GIS Notes PDF

**Introduction** This course is basically aimed at introducing the students to the science, art and technology of Geographic Information Systems (GIS). Some of the basic concepts, components, functions and application of GIS will be introduced in the course. Presented below is a synopsis of the cor...

**Introduction** This course is basically aimed at introducing the students to the science, art and technology of Geographic Information Systems (GIS). Some of the basic concepts, components, functions and application of GIS will be introduced in the course. Presented below is a synopsis of the core course contents. **Objectives** i. To formerly introduce the students to the science and technology of geographical information systems ii. To give a synopsis of the entire course. **Main Body** Since its inception in the early 1960s, Geographical Information System (GIS), as we know it today, has been growing by leaps and bounds. Originally developed by Geographers, GIS has become a powerful tool useful to all and sundry who handle geospatial data. Traditionally, we have long used maps as a method of storing and disseminating spatial data as well as exploring the earth and locating natural and cultural resources. In fact, the origins of GIS are rooted as far back as several millennia ago, when early man drew cave paintings of the animals they hunted along with crude maps depicting migration trails. While the cave paintings only vaguely resemble today's advanced geographic information systems they contain the same basic data as modern systems namely, geographic data linked with spatially dependent attribute (descriptive) information. Modern Geographic Information System (GIS) is a computer based information system used to digitally represent and analyse the geographic features and events on the Earth\' surface and the non-spatial attributes linked to the geography under study. This way, the GIS has proved itself as a robust and reliable technology for managing spatial data and as a decision support tool. Indeed GIS is rather revolutionizing the way we collect, store, visualize, analyse and use geographical data. Owing to its versatility, many disciplines can benefit from GIS technology. An active GIS market has resulted in lower costs and continual improvements in the hardware and software components of GIS. These developments will, in turn, result in a much wider use of the technology throughout science, government, business, and industry, with applications including real estate, public health, crime mapping, national defense, sustainable development, natural resources, landscape architecture, archaeology, regional and community planning, transportation and logistics. GIS is also diverging into location-based services (LBS). LBS allows GPS enabled mobile devices to display their location in relation to fixed assets (nearest restaurant, gas station, fire hydrant), mobile assets (friends, children, police car) or to relay their position back to a central server for display or other processing. These services continue to develop with the increased integration of Global Positioning System (GPS) functionality with increasingly powerful mobile electronics (cell phones, PDAs, laptops) coupled with and Web-enabled operations. **Defining GIS** **Introduction** There are several definitions of GIS in existence. However, none of such definitions is universally accepted. It is difficult to agree on a single definition for GIS for the simple reason that various kinds of GISs exist, each made for different purposes and for different types of decision making. As we will see shortly in the range of definitions presented below, people offer definitions of GIS with different emphases on various aspects of GIS. **Objectives** i. To formerly define or describe GIS ii. To highlight the essential features of GIS iii. To highlight some of the spatial questions that GIS can help us answer easily **Main Body** Definition of GIS Geographic Information System (GIS) has been defined in various ways by different authorities. A typical GIS can be understood by looking at its various definitions. In this section, therefore, we present a selection of the numerous definitions (or descriptions) of GIS that have been offered by people. GIS is a \"Set of tools for collecting, storing, retrieving at will, transforming and displaying spatial data from the real world for a particular set of purposes\" (Burrough, 1986). GIS is \"a computer based system that provides four sets of capabilities to handle geo-referenced data: data input, data management (data storage and retrieval), manipulation and analysis, and data output." (Arnoff, 1989). \"... The purpose of a traditional GIS is first and foremost spatial analysis. Therefore, capabilities may have limited data capture and cartographic output. Capabilities of analyses typically support decision making for specific projects and/or limited geographic areas. The map data-base characteristics (accuracy, continuity, completeness, etc.) are typically appropriate for small-scale map output. Vector and raster data interfaces may be available. However, topology is usually the sole underlying data structure for spatial analyses.\" (Huxhold, 1991). \"A geographic information system is a facility for preparing, presenting, and interpreting facts that pertain to the surface of the earth. This is a broad definition... a considerably narrower definition, however, is more often employed. In common parlance, a geographic information system or GIS is a configuration of computer hardware and software specifically designed for the acquisition, maintenance, and use of cartographic data.\" (Tomlin, 1990). \"A geographic information system (GIS) is an information system that is designed to work with data referenced by spatial or geographic coordinates. In other words, a GIS is both a database system with specific capabilities for spatially-reference data, as well \[as\] a set of operations for working with data... In a sense, a GIS may be thought of as a higher-order map.\" (Star and Estes, 1990). A GIS is \"an organized collection of computer hardware, software, geographic data, and personnel designed to efficiently capture, store, update, manipulate, analyze, and display all forms of geographically referenced information.\" (ESRI, 1990). "A Geographic Information System (GIS) is a collection of computer hardware, software and geographic data used to analyse and display geographically referenced information.". "A GIS is a computer system capable of capturing, storing, analyzing, and displaying geographically referenced information; that is, data identified according to location. Practitioners also define a GIS as including the procedures, operating personnel, and spatial data that go into the system.". "In the strictest sense, a GIS is a computer system capable of assembling, storing, manipulating, and displaying geographically referenced information, i.e. data identified according to their locations. Practitioners also regard the total GIS as including operating personnel and the data that go into the system.". "GIS is an integrated system of computer hardware, software, and trained personnel linking topographic, demographic, utility, facility, image and other resource data that is geographically referenced." **Essential features of GIS** - From the foregoing it is obvious that a geographic information system (GIS) is a computer-based tool that combines the visual appeal of conventional maps with database operations and statistical analysis. - It is used for mapping and analyzing things that exist and happen on the surface of the Earth by classifying the information into \"layers\", making it easy for users to distinguish each element separately. - The speed and accuracy of a GIS provide an invaluable service to organizations, by explaining events, predicting outcomes and planning future strategies. Irrespective of the definition one is giving or adopting, it must be realized that GIS is a peculiar technology with the essential features of spatial references and data analysis. Hence, the true power of GIS lies in its ability to integrate information and to help in making decisions. - A GIS integrates hardware, software, and data for capturing, managing, analyzing, and displaying all forms of geographically referenced information. - GIS allows us to view, understand, question, interpret, and visualize data in many ways that reveal relationships, patterns, and trends in the form of maps, globes, reports, and charts. GIS is a technological field that incorporates geographical features with tabular data in order to map, analyze, and assess real-world problems. The key word to this technology is Geography -- this means that the data (or at least some portion of the data) is spatial, in other words, data that is in some way referenced to locations on the earth. Coupled with this data is usually tabular data known as attribute data. **Attribute data** can be generally defined as additional information about each of the spatial features. An example of this would be schools. The actual location of the schools is the spatial data. Additional data such as the school name, level of education taught, student capacity would make up the attribute data. It is the partnership of these two data types that enables GIS to be such an effective problem solving tool through spatial analysis. GIS operates on many levels. On the most basic level, GIS is used as computer cartography, i.e. mapping. The real power in GIS is through using spatial and statistical methods to analyze attribute and geographic information. The end result of the analysis can be derivative information, interpolated information or prioritized information. A GIS is an information system designed to work with data referenced by spatial / geographical coordinates. In other words, GIS is both a database system with specific capabilities for spatially referenced data as well as a set of operations for working with the data. It may also be considered as a higher order map. GIS technology integrates common database operations such as query and statistical analysis with the unique visualization and geographic analysis benefits offered by maps. These abilities distinguish GIS from other information systems and make it valuable to a wide range of public and private enterprises for explaining events, predicting outcomes, and planning strategies. (ESRI) "A geographic information system (GIS) is a computer-based tool for mapping and analyzing things that exist and events that happen on earth. GIS technology integrates common database operations such as query and statistical analysis with the unique visualization and geographic analysis benefits offered by maps." (ESRI). Many professionals, such as foresters, urban planners, and geologists, have recognized the importance of spatial dimensions in organising & analysing information. Whether a discipline is concerned with the very practical aspects of business, or is concerned with purely academic research, geographic information system can introduce a perspective, which can provide valuable insights as - 70% of the information has geographic location as its denominator making spatial analysis an essential tool. - Ability to assimilate divergent sources of data both spatial and non-spatial (attribute data). - Visualization Impact - Analytical Capability - Sharing of Information In a nutshell, GIS is a special-purpose digital database in which a common spatial coordinate system is the primary means of reference. A full-fledged, comprehensive GIS has dedicated facilities or subsystems for: - Data input, from maps, aerial photos, satellites, surveys, and other sources - Data storage, retrieval, and query - Data transformation, analysis, and modeling, including spatial statistics - Data reporting, such as maps, reports, and plans **Questions that GIS can answer** We can gain a deeper understanding of GIS by looking at the type of questions the technology can (or should be able to) answer. GIS can be used to address concerns relating to location, condition, trends, patterns, modelling, spatial questions, as well as aspatial (non-spatial) questions. Basically, we can identify five broad types of questions that a sophisticated GIS can answer. **Location**: What is at.............? This question seeks to find out what exists at a particular location. A location can be described in many ways, using, for example place name, post code, or geographic reference such as longitude/latitude. **Condition**: Where is it.............? In this question, instead of seeking to identify what exists at a given location, one may wish to find location(s) where certain conditions are satisfied (e.g., all rentable 3-bed room apartments in a neighbourhood, sites suitable for the construction of a cement industry, an unforested section of at-least 2000 square meters in size, within 100 meters of road, and with soils suitable for supporting buildings) **Trends**: What has changed since..............? This question involves seeking to know what has changed over a given period of time, as well as the magnitude and spatial pattern of such a change (e.g. change in land use or elevation over time). **Patterns**: What spatial patterns exist..............? This question is more sophisticated. One might ask this question to determine whether, for instance, landslides are mostly occurring near streams. It might be just as important to know how many anomalies there are that do not fit the pattern and where they are located. **Modelling**: What if.................? \"What if...\" questions are posed to determine what happens, for example, if a new road is added to a network or if a toxic substance seeps into the local ground water supply. Answering this type of question requires both geographic and other information (as well as specific models). GIS permits spatial operations. **Aspatial Questions** \"What\'s the average number of people working as Estate Surveyors and Agents in each location?\" is an aspatial question - the answer to which does not require the stored value of latitude and longitude; nor does it describe where the places are in relation with each other. **Spatial Questions** \"How many people work with Estate Firms in the major urban centres of Lagos Metropolis?\" OR \"Which centres lie within 10 Kms. of each other? \", OR \" What is the shortest route passing through all these centres\". These are spatial questions that can only be answered using latitude and longitude data and other information such as the radius of earth. Geographic Information Systems can answer such questions. **Conclusion:** GIS is basically a computer-based system for comprising hardware, software, geographically referenced data, people and procedures logically arranged to store, retrieve, manipulate, analyze, update and output data (as information), for decision making. This way, GIS should be rightly seen as a powerful decision support system (DSS). **History of GIS development** **Introduction** Man has always used geographical information. Geographical features and data describing them form part of our everyday lives. Indeed most of the decisions we make on a daily basis are influenced by some aspect of Geography. Hence one would be right to say that, generally speaking geographical information system is as old as man himself. However, in this unit our focus is on modern geographical information system. We will briefly look at the emergence and growth of GIS as well as the underlying factors. **Objectives** i. To trace the historical evolution of GIS ii. To highlight the factors responsible for the growth of GIS **Main body** **History of development** It is commonly believed that the more sophisticated modern GIS can be traced back to John Snow's 1854 map of the distribution of incidences of cholera in 19th century London. While it is only a fairly basic 2-dimensional rendering, Snow's map is a useful tool to demonstrate the data analysis possibilities of GIS. When viewed in isolation, a list of cholera cases suggests nothing as to the origin of the outbreak. When that same data is translated into a GIS map the data takes on new meaning, allowing the analyst to track down the outbreak to an infected water pump (the Broad Street Pump) in the centre of a cluster. When the pump's handle was disconnected the outbreak was terminated, giving the authorities the opportunity to curtail the cholera outbreak and save lives. While the basic elements of topography and theme existed previously in cartography, the John Snow map was unique, using cartographic methods not only to depict but also to analyze clusters of geographically dependent phenomena for the first time. The early 20th century saw the development of photolithography, by which maps were separated into layers. Computer hardware development led to general-purpose computer \"mapping\" applications by the early 1960s. Work on GIS began in late 1950s. Canada was the pioneer in the development of GIS as a result of innovations dating back to late 1950s and early 1960s. Much of the credit for the early development of GIS goes to Dr. Roger Tomlinson. The year 1962 saw the development of the world\'s first true operational GIS in Ottawa, Ontario, Canada by the Federal Department of Forestry and Rural Development. Developed by Tomlinson and his team, it was called the \"Canada Geographic Information System\" (CGIS) and was used to store, analyze, and manipulate data collected for the Canada Land Inventory (CLI) -- an effort to determine the land capability for rural Canada by mapping information about soils, agriculture, recreation, wildlife, waterfowl, forestry, and land use at a scale of 1:50,000. A rating classification factor was also added to permit analysis. CGIS was the world\'s first such system and an improvement over \"mapping\" applications as it provided capabilities for overlay, measurement, and digitizing/scanning. It supported a national coordinate system that spanned the North American continent, coded lines as \"arcs\" having a true embedded topology, and it stored the attribute and locational information in separate files. As a result of this, Tomlinson has become known as the \"father of GIS,\" particularly for his use of overlays in promoting the spatial analysis of convergent geographic data. CGIS lasted into the 1990s and built a large digital land resource database in Canada. It was developed as a mainframe computer based system in support of federal and provincial resource planning and management. Its strength was continent-wide analysis of complex datasets. The CGIS, however, was never available in a commercial form. In 1964, Howard T. Fisher formed the Laboratory for Computer Graphics and Spatial Analysis at the Harvard Graduate School of Design (LCGSA 1965-1991), where a number of important theoretical concepts in spatial data handling were developed, and which by the 1970s had distributed seminal software code and systems, such as \'SYMAP\', \'GRID\', and \'ODYSSEY\' \-- which served as literal and inspirational sources for subsequent commercial development---to universities, research centers, and corporations worldwide. By the early 1980s, M&S Computing (later Intergraph), Environmental Systems Research Institute (ESRI), CARIS (Computer Aided Resource Information System) and ERDAS emerged as commercial vendors of GIS software, successfully incorporating many of the CGIS features, combining the first generation approach to separation of spatial and attribute information with a second generation approach to organizing attribute data into database structures. In parallel, the development of two public domain systems began in the late 1970s and early 1980s. The Map Overlay and Statistical System (MOSS) project started in 1977 in Fort Collins, Colorado under the auspices of the Western Energy and Land Use Team (WELUT) and the U.S. Fish and Wildlife Service. GRASS GIS was begun in 1982 by the U.S. Army Corps of Engineering Research Laboratory (USA-CERL) in Champaign, Illinois, a branch of the U.S. Army Corps of Engineers to meet the need of the U.S. military for software for land management and environmental planning. The later 1980s and 1990s industry growth were spurred on by the growing use of GIS on Unix workstations and the personal computer. By the end of the 20th century, the rapid growth in various systems had been consolidated and standardized on relatively few platforms, and users were beginning to export the concept of viewing GIS data over the Internet, requiring data format and transfer standards. More recently, a growing number of free, open source GIS packages run on a range of operating systems and can be customized to perform specific tasks. Increasingly geospatial data and mapping applications are being made available via the World Wide Web. Computerized mapping and spatial analysis have been developed simultaneously in several related fields. The present status of GIS would not have been achieved without close interaction between various fields such as utility networks, cadastral mapping, topographic mapping, thematic cartography, surveying and photogrammetry remote sensing, image processing, computer science, rural and urban planning, earth science, and geography. **Factors Aiding the rise of GIS.** Certain developments over the centuries have been cumulatively instrumental to the emergence and subsequent growth of the GIS technology. Such factors include: - Revolution in Information Technology. - Computer Technology. - Remote Sensing. - Global Positioning System. - Communication Technology. - Rapidly declining cost of Computer Hardware, and at the same time, exponential growth of operational speed of computers. - Enhanced functionality of software and their user-friendliness. - Visualizing impact of GIS corroborating the Chinese proverb \"a picture is worth a thousand words.\" **Conclusion** The management of geographical data has a long and rich history. Modern sophisticated computer-based GIS, however, is a relatively new innovation. Nonetheless, since its formal inception in the early 1960s the GIS industry has been growing by leaps and bounds. Advancements in the field of GIS have been taking place faster than anticipated. The technology is steadily making great inroads into virtually every facet of human endeavour. **Geographical Data** Introduction GIS is used to manage data. In fact, the ultimate essence of using a GIS is to provide the user with information that can be used to make sound decision and solve some real-world problems. But our concern here is primarily with geographical data or geographical information. Hence, to properly understand and appreciate the workings of GIS and how it is used to handle data, there is need for us to first comprehend the nature and importance of that data. **Objectives** - To define geographical data - To understand the nature/characteristics of geographical data - To identify the types/classes of geographical data - To highlight the value of geographical data **What is Geographical Data?** Geographical data (also known as spatial data) can be defined as any data that has locational or positional identity with respect to the surface of the earth. In other words, geographical data gives us some information about a geographical object or event. Simply put, a geographical object or feature is anything, anywhere. Anything that exists on or in relation to the Earth's surface is a geographical object; similarly, any event that takes place on or in relation to the Earth's surface is a geographical event. So, facts and figures that help us to identify the location and other spatial dimensions of any geographical phenomenon are geographical data. **Characteristics of Geographical Features** Geographical features have some characteristics which the GIS technology uses to manipulate geographical data. The major characteristics are: i. **Location**: Every geographical phenomenon has a locational or positional identity which can be used to know exactly where it is on or in relation to the surface of the Earth. The relative location of an object can be defined using geographical coordinates (latitude and longitude) or some other form of position identification. ii. **Size**: There is a great variety in the magnitude of geographical phenomena. Some are small in size e.g. insects, rats, etc., while some are quite gigantic e.g. mountains, oceans, settlements etc. iii. **Dimensions**: Every geographical feature has some geometric dimension(s). Hence each feature can be identified as a point, linear, areal, or volumetric feature. (See the sub-section on types/classes of geographical objects below). iv. **Shape**: Geographical objects have shape. Natural features commonly have irregular shapes while most of the man-made features have regular shapes. v. **Distributed**: Geographical phenomena are distributed over space. Some features are highly dispersed while some are clustered together. Similarly, while some features, especially natural features, are more randomly distributed, some others, especially man-made features, tend to be more evenly or regularly distributed. Some geographical objects are considered to be discrete in their distribution; they are not found everywhere, instead they exist at distinct locations e.g. bus stops, boreholes, lakes, etc. On the other hand, some other geographical features are ubiquitous in their distribution; they cover a vast area at varying degrees, e.g. population, temperature, rainfall, soil, etc. vi. **Relationship**: No geographical feature exists in isolation; in various ways and degrees they relate and interact with one another. A geographical feature can be located close to or far away from another feature. Also a feature can be locate to the north, east, south, or west of another; just as it could be on the left or right side of another feature. Features could be adjacent to each other; they could also be contiguous to one another in which case they share common boundaries; they can also be widely separated. Similarly features could intersect, just as one feature could lie completely inside another feature. The spatial relationships mentioned above are the key to all GIS-based analysis. **Types/Classes of Geographical Features** There is a wide range of geographical features in existence. Traditionally, however, all geographical features are grouped into four namely, point, linear, areal (polygon), and volumetric features. This grouping is done based on the geometric dimensions of the features. i. **Point features**: These are features that exist at a single spot without appreciable length and breadth. Hence, point features are considered to be zero dimensional (0-dimensional or 0-D) in nature. Examples include boreholes, bus stops, electrical transformers, etc ii. **Line or linear features**: They are considered to be one dimensional (1-dimensional or 1D) in nature; it is the length of such features that is usually taken into account. Examples are roads, rivers, railways, etc. iii. **Areal or polygonal features**: These are features that occupy a considerably large expanse of space. Both the length and breadth dimensions of such features are usually considered in their measurement; hence they are treated as two dimensional (2-dimensional or 2-D) features. Examples are lakes, farmlands, local government areas, etc. iv. **Volumetric features**: these are three dimensional (3-dimensional or 3-D) features. Their length, breadth and height (or depth, or quantity as the case may be) are usually measured. Examples include mountains, population, vehicular traffic, and air mass. **The value of Geographical data** - About 80% or more of the data man uses on a daily basis is geographical in nature. In other words, the decisions and actions we take daily are largely based on information that has geographical content. - This should not really be quite surprising, especially when we realize that virtually every activity of man takes place in geographical space. - Geographical data or information helps us to understand our environment and, hence, to exploit the available resources in the most productive, sustainable and beneficial manner. - More so, geographical information enables us to navigate our environment in an intelligent way. - Questions relating to the spatial location, distribution, relationship and accessibility of various phenomena are best answered using geographical information. - In other words, geographical knowledge helps us erase locational ignorance by affording us the opportunity of identifying events and features within a spatial frame. Geographical features and data describing them are part of our everyday lives. Most of our daily decisions are influenced by some aspect of Geography. **Conclusion** GIS makes use of geo-referenced data to function. An understanding of the peculiar nature of geographical data, therefore, is critical to proper handling of the data in a GIS environment. Before entering a piece of geo-data into a GIS environment, the type or class of the data has to be defined; similarly, the type of analysis it would be used for has to be known. Unless a piece of data is given a geographical identity in a GIS environment it will be almost impossible to process the data to yield the desired result. It therefore behoves a potential user of the GIS technology to sufficiently understand the true nature of geographical data; this will help the user in knowing how to handle the data in GIS. GIS versus Allied Technologies. **GIS VERSUS ALLIED TECHNOLOGIES** **Introduction** There are so many terms and technologies that are related to GIS. The use of so many acronyms, synonyms, and terms with related meaning to GIS can actually cause some confusion. Therefore aimed at assisting the student to know some of the various terms and technologies that are allied to GIS and to know the similarities and dissimilarities between GIS and those other technologies. **Objectives** - To highlight some acronyms, synonyms and terms related to GIS. - To identify some information technologies that are related to GIS. - To differentiate between GIS and other related technologies. **Related Terms: Acronyms, Synonyms, and More** As noted earlier one reason why it can be difficult to agree on a single definition for GIS is that various kinds of GIS exist, each made for different purposes and for different types of decision making. A variety of names have been applied to different types of GIS to distinguish their functions and roles. Some of the most widely used related terms include: - AGIS (Automated Geographic Information System) - AM/FM (Automated Mapping and Facilities Management). AM/FM is designed specifically for infrastructure management. Automated mapping by itself allows storage and manipulation of map information. AM/FM systems add the ability to link stores of information about the features mapped. However, AM/FM is not used for spatial analysis, and it lacks the topological data structures of GIS. - CAD (Computer-Assisted Drafting): These systems were designed for drafting and design. They handle spatial data as graphics rather than as information. While they can produce high-quality maps, generally they are less able to perform complex spatial analyses. - CAM (Computer-Assisted Mapping, or Manufacturing) - Computerized GIS - Environmental Information System - GIS (Geographic Information System) - Geographically Referenced Information System - Geo-Information System - Image-Based Information System - LIS (Land Information System) - Land Management System - Land Record System - Land Resources Information System - Multipurpose Cadastre: Multipurpose Geographic Data System Multipurpose Land Record System - Natural Resources Inventory System Natural Resources Management Information System Planning Information System Resource Information System - Spatial Data Handling System Spatial Database Spatial Information System **GIS and Related Systems** There are some systems that are similar in both function and name to GIS. Nevertheless such systems are not really geographic information systems as defined above. Broadly, these similar systems do not share GIS\'s ability to perform complex analysis. Computer-Aided Drafting (CAD) systems, for example, are sometimes confused with GIS. Not long ago, a major distinction existed between GIS and CAD, but their differences are beginning to disappear. CAD systems, used mainly for the precise drafting required by engineers and architects, they are also capable of producing maps though not designed for that purpose. However, CAD originally lacked coordinate systems and did not provide for map projections. Nor were CAD systems linked to data bases, an essential feature of GIS. These features have been added to recent CAD systems, but geographic information systems still offer a richer array of geographic functions. Uluocha (2007) has identified the similarities and differences between GIS and CAD. Such similarities and differences are discussed below. **Similarities between GIS and CAD** i. Both systems have similar requirements for capturing, storing and displaying graphic images interactively. ii. Interactive commands for entering lines or symbols and for editing, moving, modifying and deleting features are required for both applications. iii. Existing (analogue) maps (in the case of GIS) and drawings (in the case of CAD), must be digitised. iv. Both applications require capabilities for operations such as annotation, labelling, calculation of length, distance and area. v. Both types of systems require similar computer hardware devices such as processor, disk, tape, workstation, digitizer, scanner, and plotter. vi. Both have requirements for the linking of attribute data with their graphic entities. **Differences between GIS and CAD** i. GIS makes use of maps ranging from large to small scales whereas engineering drawings used in CAD applications usually have very large scales. ii. GIS applications unlike their CAD counterpart, generally require complex and large volume of attribute data. iii. Whereas GIS operations involve complex geographic analysis and modelling of geographic features, CAD applications deal with sophisticated engineering calculations and modelling of engineering structures. iv. GIS makes use of standard map projections while CAD does not. Simple local plane coordinates are usually enough for engineering drawings. v. GIS has powerful facilities for numerous attribute data processing operations; CAD, on the other hand, has more limited attribute processing capabilities. vi. GIS handles many spatial features such as soil, vegetation, elevation, boundaries, population and infrastructural facilities like roads, sewers, electricity, water, and so on; and also covers a wide geographic area like city, local government, state, country or even the entire earth. On the other hand, CAD applications deal with a specific or single project like the engineering design of a road segment, water or sewer line, electrical wiring, and so on. Such designs are usually done at a very large scale hence they cover very small geographic area. vii. GIS applications use topological data structure that allows for the geographic analysis of the data based on the spatial relationships among map elements. CAD applications do not require a topological data structure. viii. A GIS can be used to perform geographic analytical tasks such as polygon overlay analysis, network tracing and routing, buffering and delineation of service area, district, ecological zone, and so on. A CAD on the other hand, is used for carrying out engineering analysis and calculation functions. ix. GIS is usually used for constant updating of map features, which are known to change frequently. On the other hand, engineering drawings (and structures) hardly change. However, if a major change should occur which may necessitate altering the original concept or structure, an entirely new drawing is produced rather than updating the original drawing. **Conclusion** There are many digital data processing systems that use geo-referenced data. However, it is not every computer-based system that utilizes geospatial data that can be considered to be a geographical information system. There are notable similarities as well as differences between GIS and some allied technologies. What distinguish the GIS system from other information systems are its spatial analysis functions. The analysis functions in GIS use the spatial and non-spatial attributes in the database to answer questions about the real world. **Components of GIS\]** **GIS Hardware** **Introduction** There are many specialized hardware associated with GIS operations. Hardware comprises the physical electronic equipment needed to support the many activities of GIS ranging from data collection to data analysis and output. In this Unit we will look at the computer, data input devices, data storage devices, data output devices, and other related hardware devices. **Objectives** 1\. To identify the hardware components of a typical GIS. 2\. To discuss the functions of each of the hardware devices. **Main Body** **Computer** It consists of the computer system on which the GIS software will run. The computer forms the backbone of the GIS hardware. The central piece of equipment is the workstation, which runs the GIS software and is the attachment point for ancillary equipment. The choice of hardware system ranges from 300MHz personal computers (PCs) to multi-user supercomputers having capability in Tera FLOPS. The computer contains the processor, which is used to manage and manipulate the database based on certain rules and commands. **Input Devices** The input devices are used to capture or enter data into the computer. There are two broad categories that are usually handled in a GIS environment namely, spatial data and aspatial (attribute or descriptive) data. The spatial data can be entered into the computer with the aid of a digitizer or a scanner. A digitizer is a flat electronic board used for vectorisation of a given map objects. In other words, a digitizer is used for conversion of the drawings on an analogue or hard copy map to digital data. On the other hand, a scanner converts an analogue image or picture into a digital image for further processing. The image data acquired via a scanner can be stored in many formats e.g. TIFF, BMP, JPG etc. The use of handheld field technology is also becoming an important data collection tool in GIS. For instance, data collection efforts can also require the use of a Global Positioning System (GPS) data logger to collect data in the field. The attribute (statistical or non-spatial data) used in GIS are keyed into the computer using the keyboard. A Trimble handheld GPS receiver **Storage devices** The storage devices include various media such as optical hard disk, magnetic tape, CD, Flash drive. **Output devices** Output devices are used to obtain the hardcopy versions of processed data. Printers and plotters are the most common output devices for a GIS hardware setup. Presently, printers can only be used to obtain print-outs on paper as large as A3, whereas there are plotters that can draft on paper as large as A0. **Others** With the advent of web-enabled GIS, web servers have also become an important piece of equipment for GIS. **Conclusion** In a typical GIS environment various digital hardware devices are used. Some of the devices such as GPS, digitizer, and plotter are rather peculiar to GIS and similar systems, which handle geographical data. The capabilities of these devices can make or mar the success of GIS operations. **GIS Software** **Introduction** In computing, the software is the component that drives the hardware and data using certain methods and rules. There are a number of software packages that are used in GIS operations. GIS software packages are designed to handle geographical or spatial data. In this Unit we will learn about the nature as well as types of GIS software. **Objectives** 1\. To understand what a GIS software is. 2\. To identify different types /makers of GIS software. **Main Body** What is a GIS software? Generally, software is a digital language comprising of a set(s) of rules, commands, algorithms or programs, logically and systematically written to perform certain tasks. The software elements allow the user to input, store, manage, transform, analyse and output data (Heywood, Cornelius, and Carver, 1998). Basically, a GIS software is a package of programs, rules or commands used to perform certain GIS operations such as the input, storage, retrieval, editing, querying, analysis, manipulation, update, display and output of geographic data, in a computer environment (Uluocha, 2007). GIS software encompasses a broad range of applications, all of which involve the use of some combination of digital maps and georeferenced data. In the main, GIS software provides the functions and tools needed to store, analyze, and display geographic information. Different software packages are important for GIS. Central to this is the GIS application package. Such software is essential for creating, editing and analyzing spatial and attributes data; therefore these packages contain a myriad of GIS functions inherent to them. Extensions or add-ons are software that extends the capabilities of the GIS software package. Component GIS software is the opposite of application software. Component GIS seeks to build software applications that meet a specific purpose and thus are limited in their spatial analysis capabilities. Utilities are standalone programs that perform a specific function. For example, a file format utility that converts from one type of GIS file to another. There is also web GIS software that helps serve data through Internet browsers. Typical GIS software consists of four distinct but interrelated subsystems or modules. These are: Data input software subsystem (used for e.g. digitising or scanning, checking, editing, topology building, etc). Data storage and retrieval software subsystem. Data manipulation and analysis software subsystem (e.g. for querying, sorting or indexing, overlay operations, buffer creation, etc.) Data output software subsystem (e.g. for screen display, page set-up formatting, hard copy generation, etc.) **Types of GIS software** Numerous GIS software packages are nowadays available which cover all sectors of geospatial data handling. However, the GIS software systems can be sorted into different categories. Presented below is a list of some notable GIS software packages. It should be noted that some of the packages mentioned are also used for digital cartographic (map-making), CAD, and remote sensing (image processing) operations. (For more details on GIS software packages and their manufacturers, see Uluocha, 2007). - GRASS GIS -- Originally developed by the U.S. Army Corps of Engineers, open source: a complete GIS - SAGA GIS -- System for Automated Geoscientific Analysis- a hybrid GIS software. SAGA has a unique Application Programming Interface (API) and a fast growing set of geoscientific methods, bundled in exchangeable Module Libraries. - Quantum GIS -- QGIS is an Open Source GIS that runs on Linux, Unix, Mac OS X, and Windows. - MapWindow GIS -- Free, open source GIS desktop application and programming component. - ILWIS -- ILWIS (Integrated Land and Water Information System) integrates image, vector and thematic data. - gvSIG -- Open source GIS written in Java. - JUMP GIS / OpenJUMP -- (Open) Java Unified Mapping Platform (the desktop GIS OpenJUMP, SkyJUMP, deeJUMP and Kosmo emerged from JUMP; - Whitebox GAT -- Open source and transparent GIS software - Kalypso (software) -- Kalypso is an Open Source GIS (Java, GML3) and focuses mainly on numerical simulations in water management. - TerraView -- GIS desktop that handles vector and raster data stored in a relational or georelational database, i.e. a frontend for TerraLib. - Capaware -- Capaware is also an Open Source GIS, an incredible fast C++ 3D GIS Framework with a multiple plugin architecture for geographic graphical analysis and visualization. - FalconView -- FalconView is a mapping system created by the Georgia Tech Research Institute for the Windows family of operating systems. A free, open source version is available. - PostGIS -- Spatial extensions for the open source PostgreSQL database, allowing geospatial queries. - MySQL Spatial - TerraLib is a spatial DBMS and also provides advanced functions for GIS analysis. - Spatialite -- Spatial extensions for the open source SQLite database, allowing geospatial queries. - GeoNetwork opensource -- A catalog application to manage spatially referenced resources - Chameleon -- Environments for building applications with MapServer. - MapPoint, a technology (\"MapPoint Web Service,\" previously known as MapPoint.NET) and a specific software program created by Microsoft that allows users to view, edit and integrate maps. - Autodesk -- Products include Map 3D, Topobase, MapGuide and other products that interface with its flagship AutoCAD software package. - Bentley Systems -- Products include Bentley Map, Bentley PowerMap and other products that interface with its flagship MicroStation software package. - ERDAS IMAGINE by ERDAS Inc; products include Leica Photogrammetry Suite, ERDAS ER Mapper, and ERDAS ECW JPEG2000 SDK (ECW (file format))are used throughout the entire mapping community (GIS, Remote Sensing, Photogrammetry, and image compression). - ESRI -- Products include ArcView 3.x, ArcGIS, ArcSDE, ArcIMS, ArcWeb services and ArcGIS Server. - Intergraph -- Products include GeoMedia, GeoMedia Professional, GeoMedia WebMap, and add-on products for industry sectors, as well as photogrammetry. - MapInfo by Pitney Bowes -- Products include MapInfo Professional and MapXtreme. - Smallworld -- developed in Cambridge, England (Smallworld, Inc.) and purchased by General Electric and used primarily by public utilities. - Cadcorp -- Products include Cadcorp SIS, GeognoSIS, mSIS and developer kits - Caliper -- Products include Maptitude, TransModeler and TransCAD - ENVI - Utilized for image analysis, exploitation, and hyperspectral analysis. - Manifold System -- GIS software package. - Netcad -- Desktop and web based GIS products developed by Ulusal CAD ve GIS Çözümleri A.Ş. - Dragon/ips -- Remote sensing software with some GIS capabilities. - Field-Map : GIS tool designed for computer aided field data collection, used mainly for mapping of forest ecosystems. - VISIONLABS -- Products - VISION Enterprise GIS Suite earlier named VISION MapMaker, Complete 2D/3D mapping - Installations in Indian Govt and Defence - RegioGraph by GfK GeoMarketing; GIS software for business planning and analyses; company also provides compatible maps and market data. - IDRISI -- GIS and Image Processing product developed by Clark Labs at Clark University. Affordable and robust, it is used for both operations and education. - Boeing\'s Spatial Query Server spatially enables Sybase ASE. - DB2 -- Allows spatial querying and storing of most spatial data types. - Informix -- Allows spatial querying and storing of most spatial data types. - Microsoft SQL Server 2008 -- The latest player in the market of storing and querying spatial data. At this stage only some GIS products such as MapInfo and Cadcorp SIS can read and edit this data while ESRI and others are expected to be able to read and edit this data within the next few months - Oracle Spatial -- Product allows users to perform complex geographic operations and store common spatial data types in a native Oracle environment. Most commercial GIS packages can read and edit spatial data stored in this way. - PostGIS -- a spatial database based on the free PostgreSQL database - Safe Software -- Spatial ETL products including FME Desktop, FME Server and the ArcGIS Data Interoperability Extension. - Mapnik - C/Python library for rendering - used by OpenStreetMap - GeoServer - MapGuide Open Source -- Web-based mapping server. - MapServer -- Web-based mapping server, developed by the University of Minnesota. - MapLarge -- Web-based mapping server for large datasets. Software Development Frameworks and Libraries (for web applications) Open Layers -- open source AJAX library for accessing geographic data layers of all kinds, originally developed and sponsored by MetaCarta. MapFish GeoBase (Telogis GIS software) - Geospatial mapping software available as a Software development kit, which performs various functions including address lookup, mapping, routing, reverse geocoding, and navigation. Suited for high transaction enterprise environments. **Conclusion** Not all that are called GIS software actually have the full range of GIS functionalities. Whereas some packages are general-purpose in nature, some others are thematic or dedicated to performing some specific, usually limited, tasks. Full-fledged GIS software are relatively few. **DATA** **Introduction** Data is the core of any GIS. There are two primary types of data that are used in GIS namely, spatial (or geographic) data and aspatial (attribute or descriptive) data. Documentation of GIS datasets is known as metadata. Metadata contains such information as the coordinate system, when the data was created, when it was last updated, who created it and how to contact them and definitions for any of the code attribute data. Geographic data and related tabular data can be collected in-house or purchased from a commercial data provider. A GIS will integrate spatial data with other data resources and can even use a DBMS, used by most organization to maintain their data, to manage spatial data. This lesson aims at introducing both spatial and attribute data. **Objectives** 1\. To introduce spatial data 2\. To introduce attribute data **Main Body** **Spatial data** Spatial data are used to graphically represent some real world features. The features could be material (visible), e.g. road, building, water body; or they could also be abstract (invisible) e.g. geopolitical boundaries, language, temperature. Similarly, spatial data can be obtained from primary or secondary sources. The primary data are obtained first-hand by the user while secondary data are obtained from already existing sources. The digital map forms the basic data input for GIS. The map is an abstraction or model of some aspect of reality. Geographical features are abstracted into four spatial entities namely - Point (0-dimensional) - Line (1-dimensional), - Area (2dimensional), and - Volume (3-dimensional). In practice, however, the first three entities (point, line and area) are commonly used. Point Borehole, benchmark, Bus Stop Line Road, river, railway, coastline Area Farmland, lake, forest reserve, boundary Volume Population, traffic, air mass Spatial data in GIS are usually held in a database. A geodatabase is a database that is in some way referenced to locations on the earth. Geodatabases are grouped into two different types: vector and raster. Vector data is spatial data represented as points, lines and polygons. Raster data is cell-based data such as aerial imagery and digital elevation models. The vector and raster models are discussed in greater. **Aspatial (attribute) data** Coupled with geographic data is usually data known as aspatial or attribute data. Attribute data is generally defined as additional information about each spatial feature. An attribute data gives descriptive information about some aspect of a geographical entity. Every geographical feature has some attributes. For example, a person is a geographical object located somewhere and occupying space. However, this person also has some attributes with which they can be identified e.g. name, age, complexion, height, tribal/ethnic affiliation, religion, occupation, educational level, hobby, etc. Similarly, a school is a geographical entity having various attributes such as name, address, year of establishment, owner, facilities available (e.g. classrooms, playground, library, laboratory, weather station, hostels), etc. In a GIS environment attribute data is usually housed in tabular format. This tabular database related to the map objects can also be attached or linked to the digital spatial database. **Conclusion** To successfully implement GIS data is a critical element. Data is the raw material that GIS processes to yield a highly sort after product namely, information. In a sense, data is the element that keeps the engine of GIS running. However, care must always be taken to ensure that the right data is fed into the system. Creating GIS databases could be herculean; yet once in place and routinely updated, the databases are an invaluable asset to the users. **Personnel** 1.0 Introduction Effective development and use of the GIS technology requires the involvement of a number of people performing different tasks. In a GIS environment the people are fittingly referred to as the humanware or liveware. Well-trained people knowledgeable in spatial analysis and skilled in using GIS software are essential to the GIS process. The humanware coordinates and controls all the other components of GIS. GIS personnel range from technical specialists who design and maintain the system to those who use it to help them perform their everyday work. There are three factors to the people component: education, career path, and networking. The right education is key; taking the right combination of classes. Selecting the right type of GIS job is important. A person highly skilled in GIS analysis should not seek a job as a GIS developer if they haven't taken the necessary programming classes. Finally, continuous networking with other GIS professionals is essential for the exchange of ideas as well as a support community. **2.0 Objectives** 1\. To identify the various groups of GIS personnel. 2\. To identify the functions of GIS personnel. **3.0 Main Body** 3.1 Engineers (hardware and software) This has to with crop of technical specialists who design and maintain the system. They include the hardware engineers who fashion various GIS hardware such as the computers (CPU) and accessories like visual display units (VDUs), digitizers, scanners, disk drives, tape drives, plotters, printers and other hardware components associated with the GIS technology. On the other hand, GIS software engineers specialize in churning out computer programs and programming languages containing a set of rules (or algorithms) for solving certain spatially defined problems. **3.2 Data providers** Data providers are those who collect and/or market spatial/non-spatial data for GIS operations. The data could be acquired through field observation, land survey, GPS, aerial photography, remote sensing technique, socio-economic surveys, and so on. In Nigeria, some of the vendors of data that could be used in GIS projects are the Federal and State Survey Departments; the National Space Research and Development Agency (NASRDA); the Federal Office of Statistics (FOS); the Nigerian Meteorological Agency (NIMET); private surveying/mapping outfits; the Ministry of Environment; Geological Surveys of Nigeria; the National Population Commission (NPC); Centre for Satellite Technology Development, Abuja; National Centre for Remote Sensing, Jos; and so on. **3.3 Digitizers** These are the CAD/GIS operators whose work is to create the database; they vectorise the map objects. In other words, they are those who capture or key in or convert the data from analogue to digital or from binary to image and vector. **3.4 Programmers and Analyst** These are the GIS experts who use of the vectorised data to perform query, analysis or any other work. Their ultimate task is to generate information useful for decision making. **3.5 Managers** The GIS managers undertake administrative functions necessary for the successful implementation of the GIS technology in an organisation. They also make useful decisions based on the available geo-referenced information. **4.0 Conclusion** A team of experts is usually required to successfully install and run a GIS outfit. The quality of personnel involved in the implementation of a GIS project can make or mar the initiative. Hence, concerted effort should be made to ensure that the right calibres of personnel are used. Personnel is the most valuable asset required in the implementation of any GIS programme. **Method** **1.0 Introduction** Every task follows some laid down procedure or method; and GIS tasks are no exceptions. But the method of doing things may vary from one task to another and also from one organization to another. In any case, it is always imperative to understand the peculiar method that applies in any given situation. Unless a good understanding of the working procedure in an organization is attained, implementing GIS in that organization may as well be an exercise in futility. Hence, in this Unit we will examine the concept of method as an element of GIS. **2.0 Objectives** 1\. To underscore the need of understanding method or procedure as a major component of GIS. 2. To highlight the need to link GIS procedure with the general business of the company **3.0 Main Body** Simply put, procedure or method has to do with the ways of getting a job done in an organization. But with particular reference to GIS, method could be understood to include a well-designed GIS implementation plan in addition to business rules, which are the models and operating practices unique to each organization (Buckley, URL). Method may vary from one organization to another, depending on the objectives as well as modus operandi of each individual organization (Uluocha, 2007). The way an estate surveyor/valuer would use the GIS facility, for instance, will differ from how a geologist would use it -- since their goals and functions also differ. The essence of adopting the GIS technology in any organization is to assist the organization to attain its goals. GIS is normally used to meet the information need of an organization, which is quite crucial to decision-making. But for GIS to successfully operate in an organization it has to be appropriately integrated into the business strategy and operations of that organization. Thus, GIS should be a functional part of the entire method of data acquisition, input, storage, sorting, indexing, retrieval, analysis, output and updating, along with the process of decision making. GIS could be implemented to simply automate (fully or partially) the methods of executing certain jobs, which hitherto were manually done. This may not involve any major change in procedure except that the job is now done digitally instead of manually. Nonetheless, the adoption of GIS in an organization may necessitate a significant shift in procedure, which could see the organization adopting some entirely new methods of executing some conventional jobs (Uluocha, 2007). For instance, in a GIS environment there are various techniques used for map creation and further usage for any project. The map creation can either be done through automated raster-to-vector conversion or it can be manually vectorised on-screen using the scanned images. The source of these digital maps can be either map prepared by any survey agency or satellite imagery. An organization should be able to decide on which suitable procedure of GIS operations to adopt. Method or procedure is usually tied to the business of the company. This means before recommending and implementing GIS in a company, the various units of the establishment and the linkages amongst them coupled with the operations/tasks that are carried out must be properly understood. In other words, the method of GIS operation in a company should be dependent on the components of the company, tasks executed, the type of data/information used the pattern of information flow, the information output (product) required, and the general modus operandi of the company. In discussing or determining the GIS procedure in any organization the following should be taken into consideration: The nature of the company's business (what does the company do?) Spatial data requirements of the company. The types of geospatial data used by the company for its various activity modules. How the company collects, converts, stores, and processes its spatial database. The pattern of information flow in the company. Data accessibility policy of the company. Geospatial data handling facilities available. The cartographic (map) and allied products (outputs) required by the company. **4.0 Conclusion** Before implementing a GIS in an organization the procedure for the use of the technology should be clearly defined in line with the aim and aspirations of the organization. A successful GIS operates according to a well-designed plan and business rules. **Data Input** 1.0 Introduction Data input is a critical aspect of GIS operations. The quality of the output data is largely dependent on the quality of the underlying database. Creating a GIS database could be quite demanding; careful and rigorous planning and execution is usually required. In this Unit we will focus on such data input operations as geographical referencing, digital data conversion/data capture, data checking/editing, and data integration. **2.0 Objectives** 1\. To discuss the concept of geo-referencing. 2\. To examine the processes of spatial and attribute data input. 3. To discuss the issues of data checking and editing. **3.0 Main Body** **3.1 Projection -**Projection is a key component of map making. A projection is a mathematical means of transferring information from a model of the Earth, which represents a three-dimensional curved surface, to a two-dimensional medium---paper or a computer screen. Different projections are used for different types of maps because each projection particularly suits specific uses. For example, a projection that accurately represents the shapes of the continents will distort their relative sizes. Since much of the information in a GIS comes from existing maps, a GIS uses the processing power of the computer to transform digital information, gathered from sources with different projections and/or different coordinate systems, to a common projection and coordinate system. **3.2 Geo-referencing** \"Every object present on the Earth can be geo-referenced\", is the fundamental key of associating any database to GIS. Before using any data in a GIS environment the data should be georeferenced (Uluocha 2007). Geo-referencing (also known as geo-rectification, geolocating, geocoding or registering) is the process of assigning spatial location identity to pieces of information. In other words, it is the process of giving a cartographic material such as a digital satellite imagery, aerial photograph, map, or statistical data a real world coordinate system and map projection. Or, as Kasianchuk and Taggart (2004) simply put it, "Georeferencing is the process of establishing a relation between the data displayed in your GIS software and its realworld location." Geo-referencing enables us to know exactly where things are positioned on or in relation to the earth's surface. The geo-referencing process is normally used to relate or link cartographic data to the specific portions on the earth's surface that they represent or pertain to. Besides, georeferencing enables one to accurately measure distances, directions, sizes (areas) and shapes of features on cartographic base material. In a GIS environment, unless a piece of data is georeferenced, it would be impossible to undertake certain spatial analysis operations using the data. Georeferencing is commonly achieved by using a coordinate system. There are various spatial referencing systems in use, some of which are rather crude and simple while some are sophisticated and complex. Nevertheless, it has become somewhat customary to classify geo-referencing systems into two broad groups namely, coordinate systems and noncoordinate systems. Examples of coordinate systems are the spherical (geographic) coordinate system and the rectangular coordinate system. Non-coordinate systems include Postal Addresses and Postal Codes (or ZIP codes in USA), telephone codes, placenames, Enumeration Areas (EAs), House Numberings or Street Addresses, etc. Some common geo-coding systems are shown in Table 3.1. It should be noted, though, that some of the non-coordinate systems, e.g. telephone area codes and postal zip codes, exhibit only rudimentary metric properties and do not give information about direction or size of objects (Fabiyi, 2001, p62). For large areas such as states, countries, regions, or continents, the spherical (or geographic) grid coordinate system of latitude and longitude is more useful for geo-referencing. Conversely, the plane rectangular grid coordinate system, which makes use of x,y coordinates (or Eastings and Northings) is more suited to geo-referencing small areas like a school compound, census enumeration area, electoral district, village, ward and township. The spherical coordinate system is composed of a network of infinite number of latitudes and longitudes. The latitudes and longitudes are usually numbered or identified with angular values in degrees, minutes and seconds, e.g. 4o23'14"N, 15o07'25"E. The point of intersection between the Greenwich Meridian and the Equator forms the origin (0) in the spherical coordinate system. In the spherical grid system, the value of latitude is usually given before that of longitude. **3.3 Spatial Data capture** How can a GIS use the information in a map? If the spatial or cartographic data to be used are not already in digital form, that is, in a form the computer can recognize, various techniques can capture the information. Data capture or conversion is the technical process of entering or putting information into the computer system. Data capture involves identifying the objects on the map, their absolute location on the Earth\'s surface, and their spatial relationships. This process consumes much of the time of GIS practitioners. Nevertheless, software tools that automatically extract features from satellite images or aerial photographs are now gradually replacing what has traditionally been a time-consuming capture process. There are a variety of methods used to enter spatial data into a GIS where it is stored in a digital format. Existing spatial data printed on paper or PET film maps can be digitized or scanned to produce digital data. As earlier noted, a digitizer produces vector data as an operator traces points, lines, and polygon (areal) boundaries from a map. Maps can be digitized by hand-tracing with a computer mouse on the screen or on a digitizing tablet to collect the coordinates of features. Modern GIS technologies use digital information, for which various digitized data creation methods are used. The most common method of data creation is digitization, where a hard copy map, survey plan or chart is transferred into a digital medium through the use of a computer aided design (CAD) program, and geo-referencing capabilities. With the wide availability of ortho-rectified imagery (both from satellite and aerial sources), heads-up digitizing is becoming the main avenue through which geographic data is extracted. Heads-up digitizing involves the tracing of geographic data directly on top of the aerial imagery instead of by the traditional method of tracing the geographic form on a separate digitizing tablet (heads-down digitizing). Digitization or conversion of existing paper based records, plans, maps and charts to digital using any of the three established and tested methods: Using the Digitizing tablet manually. Using the semi-automatic raster chasing method Using the Bundle (Fully automatic) method. Electronic scanners can also convert maps to digits. Scanning a map results in raster data, which could be further processed to produce vector data through a process known as vectorization. Comparative advantages and disadvantages of the manual digitising process to the automatic scanning technique. Survey data can also be directly entered into a GIS from digital data collection systems on survey instruments using a technique called Coordinate Geometry (COGO). Positions from a Global Navigation Satellite System (GNSS) like Global Positioning System (GPS), another survey tool, can also be directly entered into a GIS. Coordinates from GPS receivers can be uploaded into a GIS. Current trend is data collection and field mapping carried out directly with field computers (position from GPS and/or laser rangefinder). New technologies allow for the creation of maps as well as data analysis directly in the field; this makes mapping projects efficient and accurate. Remotely sensed data also plays an important role in spatial data collection. This consists of sensors attached to a platform such as an aircraft or spacecraft (satellite). Sensors include cameras, digital scanners and LIDAR. Here satellites use different sensor packages to passively measure the reflectance from parts of the electromagnetic spectrum or radio waves that were sent out from an active sensor such as radar. Remote sensing collects raster data that can be further processed using different bands to identify objects and classes of interest, such as land cover. The majority of digital spatial data currently comes from photo interpretation of aerial photographs. Soft copy workstations are used to digitize features directly from stereo pairs of digital photographs. These systems allow data to be captured in two and three dimensions, with elevations measured directly from a stereo pair using principles of photogrammetry. Currently, analog aerial photos are scanned before being entered into a soft copy system, but as high quality digital cameras become cheaper this step will be skipped. Digitizing and Scanning Techniques Compared. Manual digitizing Automatic Scanning - A time-consuming procedure. - The spatial (map) data is recorded in vector format. - Can be used to selectively capture map data (the operator digitizes only the required features). This reduces the amount of time spent on cleaning and editing the data. - The procedure requires a lot of human input (labour-intensive). - The captured linework often has a high resolution, hence suitable for map production. - The source material to be digitized can easily be geo-referenced. - Suitable for small mapping projects, which involve very few map sheets. - Less time-consuming - The spatial data is recorded in raster (grid cell) format. - Automatically captures every feature on the source document (e.g. map, aerial photograph, orthophoto map, satellite imagery). This creates additional editing problem. - Requires less human input. - Resolutions of lineworks are not often high, hence not quite suitable for map production. - The process of geo-referencing source material is usually extensive. - Suitable for very large mapping and geographical analysis projects requiring the digital conversion of several map sheets, aerial photos or satellite imagery. Source: Uluocha (2007) Data restructuring can be performed by a GIS to convert data into different formats. Since digital data is collected and stored in various ways, the data sources may not be entirely compatible. Some of the data may be in vector format while some may be in raster format. So a GIS must be able to convert geographic data from one structure to another. For example, a GIS may be used to convert a satellite image (raster) map to a vector structure by generating lines around all cells with the same classification, while determining the cell spatial relationships, such as adjacency or inclusion; this process is known as raster-to-vector conversion. 3.4 Attribute Data Capture In addition to collecting and entering spatial data, attribute data is also entered into a GIS. For vector data, this includes additional information about the map objects represented in the system. A typical attribute data consists of statistical facts and figures which are usually presented in tabular form. Hence, the keyboard is the device normally used to put attribute data into the computer. If the data already exists as an electronic file, for example as a spreadsheet, it can be simply downloaded into the GIS. **3.5 Checking and Editing** The data capture process is never error-free. Hence, after capturing the geographical data or keying in the statistical (attribute) data into a GIS, the data usually requires checking and editing, to identify and remove any errors, or further processing. For vector data it must be made \"topologically correct\" before it can be used for some advanced analysis. For example, in a road network, lines must connect with nodes at an intersection. Errors such as undershoots and overshoots must also be removed. For scanned maps, blemishes on the source map may need to be removed from the resulting raster. For example, a fleck of dirt might connect two lines that should not be connected. The possible errors that could occur in a digitized map include Pseudo nodes (unwanted nodes) Overshoots and undershoots (unwanted dangling arcs/nodes) Sliver polygons (unwanted overlapping polygons) The possible attribute data entry errors include the following: Spelling errors. Entering of wrong digits (numerical figures). Wrong field naming (e.g. designating a field as "character" instead of "numeric", and vice versa). Too long or too short field width (size). Omission of some data items. Inclusion of unwanted data items. **3.6 Data Integration** A GIS makes it possible to link, or integrate, information that is difficult to associate through any other means. In other words, GIS is effectively used to relate information from different sources. Thus, a GIS can use combinations of mapped variables to build and analyze new variables For example, using GIS technology, it is possible to combine agricultural records with hydrography data to determine which streams will carry certain levels of fertilizer runoff. Agricultural records can indicate how much pesticide has been applied to a parcel of land. By locating these parcels and intersecting them with streams, the GIS can be used to predict the amount of nutrient runoff in each stream. Then as streams converge, the total loads can be calculated downstream where the stream enters a lake. The power of a GIS comes from the ability to relate different information in a spatial context and to reach a conclusion about this relationship. Most of the information we have about our world contains a location reference, placing that information at some point on the globe. For instance, when rainfall information is collected, it is important to know where the rainfall is located. This is done by using a location reference system, such as longitude and latitude, and perhaps elevation. Comparing the rainfall information with other information, such as the location of marshes across the landscape, may show that certain marshes receive little rainfall. This fact may indicate that these marshes are likely to dry up, and this inference can help us make the most appropriate decisions about how humans should interact with the marsh. A GIS, therefore, can reveal important new information that leads to better decision-making. **4 Conclusion** Data input is a major function of GIS; it is one of the most critical and cumbersome aspects of the system. Creating a robust, reliable and comprehensive database is crucial to the success of GIS operations. The quality of the outcome obtainable from GIS cannot be different from the quality of the underlying database -- it's still a case of "garbage in, garbage out". Thus in any GIS project the data input operation should be properly planned and meticulously executed **Data storage** **1.0 Introduction** Perhaps data maintenance in a GIS environment starts with having in place a good data storage system. Once a database has been created it needs to be properly stored for safe-keeping and easy access. There are various digital data storage devices available today. In this Unit we will take a quick look not only at the available devices but also the peculiar requirements and qualities of devices for the storage and handling of geospatial data. **2.0 Objectives** 1\. To identify the various electronic data storage devices used in GIS 2\. To discuss the qualities of good storage devices. 3.0 Main Body **3.1 Data storage** It's not just enough to digitally compile data; once compiled, the digital map files and the related attributes data files in the GIS should be stored on magnetic or other digital media. In a GIS environment data storage is based on a Generic Data Model that is used to convert map data into a digital form. As already identified, the two most common types of spatial data models are Raster and Vector. Both types are used to simplify the data shown on a map into a more basic form that can be easily and efficiently stored in the computer. On the other hand, the tabular Relational data model is commonly used to store attribute data. It is instructive to note that the particular model -- raster or vector \-- used to store spatial data matters a whole lot. As we have already discussed, comparatively speaking, each of the models has its own merits and demerits. Hence, in deciding on which model to choose for data storage, the intended application of the database and the expected output (end product) should be taken into consideration. Moreover, it must be borne in mind that certain operations are more efficiently executed using one type of data model than the other. **3.2 Storage devices** Various data storage devices exist for GIS configurations. These devices are commercially available in varying physical dimensions and storage densities. Conventionally, the magnetic tape and the optical disk are the two types of storage devices used in GIS. However, not too long ago the Zip Drive, compact disk (CD) and FlashDisk joined the family of computer storage media. Diskettes, which were once in vogue, are hardly in use nowadays. Usually, large storage capacities are required for GIS applications. This should be so because GIS databases apart from being traditionally large often include graphic data, which normally make high demand on computer storage space (Uluocha, 2007). Presently, optical disks with a capacity of several terabytes exist. Such very high storage capacity media can conveniently be used to handle large geographic databases. It should also be noted that for efficient and effective GIS operations, a storage device with an efficient read/write mechanism, hence a fast input/output (I/O) rate, is most desirable. Ordinarily, owing to the large volume of a typical geographic database coupled with the graphic component, it took a while to retrieve and view data in a GIS environment. However "with more efficient read/write mechanisms, higher capacity I/O channels, and intelligent disk controlling devices" (Croswell and Stephen, 1988), it is now a lot faster to retrieve, view, query and manipulate geographical databases. **3.3 Qualities of a good storage device** Owing to the fact that geospatial data are characteristically voluminous coupled with the peculiar nature of some GIS operations, a storage device that meets certain qualities is usually desirable. Fast access rate to data, which allows for real-time processing. For a storage device to be considered good enough for data storage in a GIS environment it should have the following qualities: Very high storage density, which can conveniently support the often large volume of geographic databases. Efficient read/write mechanism, Fast input/output (I/O) rate Cost effective. Durable Less prone to virus attack **4.0 Conclusion** Once the data have been digitally compiled, digital map files and the associated attributes data files in the GIS are stored on magnetic or other digital media. For smooth operations and to obtain good results, appropriate data model and robust devices must be chosen, for data storage. : Data Manipulation and Analysis 1.0 Introduction Spatial analysis is one of the major a GIS performs. There is a vast range of spatial analysis techniques that have been developed over the past half century. The subject of spatial analysis is a rapidly changing field, and GIS packages are increasingly including analytical tools as standard built-in facilities or as optional toolsets, add-ins or \'analysts\'. In many instances such facilities are provided by the original software suppliers (commercial vendors or collaborative non commercial development teams), whilst in other cases facilities have been developed and are provided by third parties. Furthermore, many products offer software development kits (SDKs), programming languages and language support, scripting facilities and/or special interfaces for developing one's own analytical tools or variants. In this session we will look at some of the spatial analytical operations that can be carried out using GIS. 2.0 Objectives 1\. To identify some of the major data manipulation and analysis operations carried out in GIS. 2. To discuss in detail some of the geographical analysis procedures. 3.0 Main Body 3.1 Data manipulation/analysis operations Although the data input is, in general, the most time consuming part, it is for data analysis that GIS is used. What distinguish the GIS system from other information system are its spatial analysis functions. The heart of GIS is the analytical capabilities of the system. The analysis functions use the spatial and non-spatial attributes in the database to answer questions about the real world. Geographic analysis facilitates the study of real-world processes by developing and applying models. Such models illuminate the underlying trends in geographic data and thus make new information available. The objective of geographical analysis is to transform data into useful information to satisfy the requirements or objectives of decision-makers at all levels in terms of detail. Results of geographical analysis are mostly communicated with the help of maps, and/or graphs (charts). GIS offers the user several data manipulation and analysis options. The facilities available in GIS for data processing functions are known as \"Toolkits.\" A toolkit is a set of generic functions that a GIS user can utilize to manipulate and analyze geographic and attribute data. Toolkits provide processing functions such as data retrieval, query, measuring area and perimeter, overlaying maps, performing map algebra, and reclassifying map data. Data manipulation tools include: Coordinate change (for changing from one geographical coordinate system to another), Projections (for changing from one map projection to another), Rescaling (for changing map scale), and Edge matching (or rubber sheeting), which allows a GIS to reconcile irregularities between map layers or adjacent map sheets called Tiles. Similarly, GIS is usually equipped with a number of analytical tools for conducting various kind of geographical analysis. Among the broad range of major geographical analysis procedures in GIS are: Database query Map overlay Proximity analysis Network analysis Digital Terrain Modeling (DTM) Statistical and Tabular Analysis. **3.2 Some geographical analysis procedures** This subsection looks briefly at some of the geographical analysis functions carried out using GIS. **3.2.1 Slope and Aspect** Slope, aspect and surface curvature in terrain analysis are all derived from neighbourhood operations using elevation values of a cell's adjacent neighbours. There are various techniques for calculating slope and aspect. Slope is a function of resolution, and the spatial resolution used to calculate slope and aspect should always be specified. **3.2.2 Data modeling** A GIS, however, can be used to depict two- and three-dimensional characteristics of the Earth\'s surface, subsurface, and atmosphere from information points. For example, a GIS can quickly generate a map with isopleth or contour lines that indicate differing amounts of rainfall. Such a map can be thought of as a rainfall contour map. Many sophisticated methods can estimate the characteristics of surfaces from a limited number of point measurements. A two-dimensional contour map created from the surface modeling of rainfall point measurements may be overlaid and analyzed with any other map in a GIS covering the same area. For example, with a GIS one can easily relate wetlands maps to rainfall amounts recorded at different points such as airports, television stations, and high schools. Additionally, from a series of three-dimensional points, or digital elevation model, isopleth lines representing elevation contours can be generated, along with slope analysis, shaded relief, and other elevation products. Watersheds can be easily defined and delineated for any given reach, by computing all of the areas contiguous and uphill from any given point of interest. **3.2.3 Topological modeling** A GIS can recognize and analyze the spatial relationships that exist within digitally stored spatial data. These topological relationships allow complex spatial modelling and analysis to be performed. Topological relationships between geometric entities traditionally include adjacency (what adjoins what), containment (what encloses what), and proximity (how close something is to something else). **3.2.4 Network Analysis** The GIS can be used to undertake various network analyses. With the GIS, for instance, one can study the network density, network characteristics, network behavior, and network function. The flow of materials and energy in a network can be modelled using GIS. Similarly, the potential impacts of a given network can equally be examined using GIS. For instance, if all the factories near a wetland were accidentally to release chemicals into the river at the same time, how long would it take for a damaging amount of pollutant to enter a recipient wetland reserve? A GIS can simulate the routing of materials along a linear network. Values such as slope, speed limit, or pipe diameter can be incorporated into network modeling to represent the flow of the phenomenon more accurately. Network modelling is commonly employed in transportation planning, hydrology modelling, and infrastructure (utility) modelling. **3.2.5 Hydrological Modeling** GIS hydrological models can provide a spatial element that other hydrological models lack, with the analysis of variables such as slope, aspect and watershed or catchment area. Terrain analysis is fundamental to hydrology, since water always flows down a slope. As basic terrain analysis of a Digital Elevation Model (DEM) involves calculation of slope and aspect, DEMs are very useful for hydrological analysis. Slope and aspect can then be used to determine direction of surface runoff, and hence flow accumulation for the formation of streams, rivers and lakes. Areas of divergent flow can also give a clear indication of the boundaries of a catchment. Once a flow direction and accumulation matrix has been created, queries can be performed that show contributing or dispersal areas at a certain point. More detail can be added to the model, such as terrain roughness, vegetation types and soil types, which can influence infiltration and evapotranspiration rates, and hence influencing surface flow. These extra layers of detail ensure a more accurate model. **3.2.6 Cartographic modeling** The term \"cartographic modeling\" refers to a process where several thematic layers of the same area are produced, processed, and analyzed to obtain a composite map. The map overlay (or simply overlay) method is generally used to achieve this. Map overlay (Fig. CCCC) involves the combination of several vector spatial datasets (points, lines or polygons) to create a new output vector dataset, visually similar to stacking several maps of the same region. These overlays are similar to mathematical Venn diagram overlays. A union overlay combines the geographic features and attribute tables of both inputs into a single new output. An intersect overlay defines the area where both inputs overlap and retains a set of attribute fields for each. A symmetric difference overlay defines an output area that includes the total area of both inputs except for the overlapping area. **3.2.7 Geostatistics** Geostatistics is a point-pattern analysis that produces field predictions from sample data points. It is a way of looking at the statistical properties of those special data. It is different from general applications of statistics because it employs the use of graph theory and matrix algebra to reduce the number of parameters in the data. When phenomena are measured, the observation methods dictate the accuracy of any subsequent analysis. Due to the nature of the data (e.g. traffic patterns in an urban environment; weather patterns across Nigeria), a constant or dynamic degree of precision is always lost in the measurement. This loss of precision is determined from the scale and distribution of the data collection. Usually the larger the sample size the more accurate will the result of the analysis be. To determine the statistical relevance of the analysis, an average is determined so that points (gradients) outside of any immediate measurement can be included to determine their predicted behavior. This is due to the limitations of the applied statistic and data collection methods, and interpolation is required to predict the behavior of particles, points, and locations that are not directly measurable. Interpolation is the process by which a surface is created, usually a raster dataset, through the input of data collected at a number of sample points. There are several forms of interpolation, each of which treats the data differently, depending on the properties of the data set. In comparing interpolation methods, the first consideration should be whether or not the source data will change (exact or approximate). Next is whether the method is subjective, a human interpretation, or objective. Then there is the nature of transitions between points: are they abrupt or gradual. Finally, there is whether a method is global (it uses the entire data set to form the model), or local where an algorithm is repeated for a small section of terrain. Digital elevation models (DEM), triangulated irregular networks (TIN), edge finding algorithms, Thiessen polygons, Fourier analysis, (weighted) moving averages, inverse distance weighting, kriging, spline, and trend surface analysis are all mathematical methods to produce interpolative data. **3.2.8 Address geocoding** Geocoding is interpolating spatial locations (X,Y coordinates) from street addresses (i.e. street names and house numbering), or any other spatially referenced data such as Postcodes or ZIP Codes, parcel lots and address locations. A reference theme is required to geocode individual addresses, such as a road centerline file with address ranges. The individual address locations have historically been interpolated, or estimated, by examining address ranges along a road or street segment. These are usually provided in the form of a table or database. The GIS will then place a dot approximately where that address belongs along the segment of centerline. For example, an address point of 50 will be at the midpoint of a line segment that starts with address 1 and ends with address 100. Geocoding can also be applied against actual parcel data, typically from municipal tax maps (cadastral maps). In this case, the result of the geocoding will be an actually positioned space as opposed to an interpolated point. This approach is being increasingly used to provide more precise location information. There are several potentially dangerous caveats that are often overlooked when using interpolation. Various algorithms are used to help with address matching when the spellings of addresses differ. Address information that a particular entity or organization has data on, such as the post office, may not entirely match the reference theme. There could be variations in street name spelling, community name, etc. Consequently, the user generally has the ability to make matching criteria more stringent, or to relax those parameters so that more addresses will be mapped. Care must be taken to review the results so as not to map addresses incorrectly due to overzealous matching parameters. **4.0 Conclusion** What distinguish the GIS system from other information system are its spatial analysis functions. As a matter of fact, the heart of GIS is the analytical capabilities of the system; it is for data analysis that GIS is used **Data Output** **1.0 Introduction** A critical component of a GIS is its ability to produce graphics on the screen or on paper to convey the results of analyses to the people who make decisions about resources. Wall maps, Internet-ready maps, interactive maps, and other graphics can be generated, allowing the decision-makers to visualize and thereby understand the results of analyses or simulations of potential events. **2.0 Objectives** 1\. To examine the issue of data display in a GIS environment 2\. To discuss document and printing formatting 3\. To look at the issue of final data output. 3.0 Main Body **3.1 Data Display** Data display is a form of data output -- softcopy output. To work interactively with the computer system the data has to be displayed. The VDU (visual display unit) also known as monitor or screen, is usually the medium of data display. Both the graphic (map and chart) and textual (attribute) data can be displayed. The attribute data is usually displayed in tabular format. The spatial data is commonly displayed in map form. Most GIS operations involve a lot of graphics; consequently, a high-resolution VDU with a powerful GUI (graphical user interface) is often desirable. There are various graphic display techniques. The VDU can be used to present spatial (map) data as a planimetric (2-D) or altrimetric (3-D) displayed, depending on the nature of the data. Traditional maps are abstractions of the real world, a sampling of important elements portrayed on a sheet of paper with symbols to represent physical objects. People who use maps must interpret these symbols. Topographic maps show the shape of land surface with contour lines or with shaded relief. Today, graphic display techniques such as shading based on altitude in a GIS can make relationships among map elements visible, heightening one\'s ability to extract and analyze information. For example, two types of data could be combined in a GIS to produce a perspective view of a portion of an area. This can be done by using the digital elevation model, consisting of surface elevations and a satellite image for the same coordinate points, pixel by pixel, as the elevation information. **3.2 Document Formatting** Before the hardcopy of a document is printed (or plotted) some form of formatting may be required. Formatting involves preparing and presenting the document in the desired final output form. This is a form of customizing the document. Thus, document formatting may involve defining certain specifications or settings relating to the document to be produced. Formatting applies to both the graphics and texts. It equally involves defining printing or plotting options. The graphics, texts and printing formatting exercises are discussed below. Graphics (map) formatting: This relates to the modifications made on the map to enhance its aesthetics and communication efficiency. The formatting exercise may include: Modifying feature colour (gray tone (black & white), or coloured). Modifying symbols. Inserting neatlines (borderlines) around the map. Choosing North Arrow symbol. Adding/modifying graticules (lines of latitude and longitude), legend and scale bar. Adding inset map. Adding/editing labels (map lettering). Proper positioning of map elements (e.g. map area, scale bar, legend box, north arrow, title, source, disclaimer, copyright, etc.), to achieve balance. Map embellishment. Text formatting: This has to do with certain modifications that could be applied to the text and font. This may involve specifying font: Type (e.g. Arial, Times New Roman, Tahoma, etc.) Colour Size (e.g. 8, 12, 36, 72 point size) Style (e.g. normal, italics, bold) Underlining Effects (e.g. shadow, panels, balloons) Orientation (horizontal, vertical, diagonal) Paper/Printing formatting: Selection of paper size (Letter, A4, A3, A2, A1, A0) Indicating paper orientation (portrait, landscape) Setting page margins Inserting page number Inserting date and other special remarks, symbols/logos, watermarks Defining printing options (e.g. gray scale, colour, number of copies, etc.) Print quality (usually specified as number of dots per inch (dpi) e.g. 300dpi, 600dpi, 1200dpi) Specifying page range to print (all, current page, pages -- to -) Selection of printer or plotter type. **3.3 Data Output** Cartographic data output is quite crucial in GIS operations. Visualization or cartographic display of spatial data in a GIS environment is a key component of GIS analytical operations. Cartography is the design and production of maps, or visual representation and communication of spatial data. The vast majority of modern cartography is done with the help of computers, usually using a GIS. Most GIS software gives the user substantial control over the appearance of the data. Cartographic work serves two major functions: First, it produces graphics on the screen or on paper that convey the results of analysis to the people who make decisions about resources. Web Map Servers facilitate distribution of generated maps through web browsers using various implementations of web-based application programming interfaces (AJAX, Java, Flash, etc.). Second, other database information can be generated for further analysis or use. An example would be a list of all building addresses within one mile (1.6 km) radius of a toxic spill. The hardcopy (paper) data output can be obtained using a printer or a plotter. Printers are used for producing relatively small size papers. Currently, the largest paper size a wide carriage printer can pri