Geospatial Data and Capture Methods

Chapter 5 Outline

• Geo spatial data
• Data capturing and data entry
• Sources of spatial data errors and its correction measures

What is Geospatial Data?

• Geospatial data has a geographic component.
• Data records include location information like coordinates, addresses, city, or ZIP codes.
• GIS data is a type of geospatial data.

Source of Data

• Field survey data
• Existing tabular data and maps
• Remote sensing data
• Aerial photographs and satellite imagery
• Soft ideas/ undocumented knowledge

Data Capture

• GIS data capture is a method to digitize map attributes, facilities, resources, and organizational information into a GIS system's layers.
• Two types of methods are commonly used
  • Primary GIS Data Capture Method
  • Secondary GIS Data Capture Method

Primary GIS Data Capture Method

• Uses surveying technologies like raster and vector data capture.

Raster Data Capture Method

• Captures attributes and data without physical contact.
• Often uses satellite imagery and aerial photography.
• Offers consistency and organization for accurate, cost-effective data.

Vector Data Capture Method

• Involves physical surveying techniques like DGPS and ETS.
• Though effective, it is often time-consuming and expensive.

Secondary GIS Data Capture Method

• Employs technologies such as scanning, manual digitizing, vectorization, photogrammetry, and feature construction to capture data.
• Scanning raster data: high-resolution scanners provide accurate raster images from hard copies, which can be georeferenced and digitized.
• Digitizing: the process of entering digital codes of analyzed data into a computer; can be manual (using digitizing tablets) or automatic (using scanners).

Data Entry

• Data input is encoding data into a computer format and recording it in the GIS database.
• Two types of data are entered in a GIS: spatial (geographic location of features) and non-spatial (descriptive or numeric details).
• Data input types include manual entry, digitizing, and scanning.

Data Storage

• Data organization within a GIS system, considering spatial and attribute data by their location and interrelationships.
• Spatial data is often stored on hard drives or diskettes.

Data Manipulation and Processing

• Data manipulation and processing provide useful information from existing data.
• Two types of operations include:
  • Editing data to remove errors and update data sets
  • Analytical operations to answer specific questions.

Data Output

• Display or presentation of data in various formats, including maps, graphs, reports, tables, and charts.
• Data can be output as hard copies, screen displays, or text files for further analysis in other programs.

Data Management and Analysis

• Used to facilitate data input, storage, management, retrieval, analysis, and presentation.
• The general procedure involves:
  • Determining the objectives of a GIS project
  • Designing the database
  • Building or creating a GIS database
  • Entering data
  • Analyzing data
  • Presenting results/information

Data management

• Data management involves securely, efficiently and cost-effectively collecting, keeping and using data.
  • This includes the process of ingesting, storing, organizing and maintaining data.
  • Data management effectively requires a data strategy and dependable methods to access, integrate, cleanse, manage and prepare data for analysis.
  • Data management skills involve the abilities to effectively manage and use information.

Errors in GIS Data

• Errors can be introduced at many points in GIS analysis, with data collection being a major source.
• Each new dataset introduces potential errors.
• Understanding data quality is essential due to the diverse sources of data.
• Errors are categorized by Burrough (1986) into:
  • Obvious sources of errors
  • Errors from natural variations or original measurements
  • Errors during processing

Errors Arising During Processing

• These errors are the hardest to detect, demanding specific knowledge of information systems.
• These errors can occur in various ways and in multiple sets which makes them potentially more insidious in GIS projects.

General Sources of Error in GIS Data

• Conception

• Measurement

• Representation

• Analysis

• GIS data errors can be corrected through careful data collection and editing.

• Good data management techniques helps to manage errors.

This quiz covers the essentials of geospatial data, including its definitions, sources, and methods of data capture. Explore the intricacies of acquiring data for geographic information systems (GIS) and understand the types of errors that can occur. Perfect for students or professionals looking to deepen their knowledge in geospatial technology.