Introduction to Maps

Introduction to Maps

• A map reduces the world to points, lines, and areas.
• These elements are defined by their positions within a coordinate system.
• Maps employ visual aids like size, value, texture, color, orientation, and shape for representation.
• Maps are often stylized, generalized, or abstracted.
• Careful interpretation is needed.
• Maps usually show only a static situation or a "time slice."
• Maps specify how objects are located in space relative to each other.

Map Definitions

• The International Cartographic Association says a map is a graphic representation on a flat medium, typically to scale.
• The representation contains a selection of material or abstract features on or related to the Earth's surface.
• M.J. Kraak & F.J. Ormeling define a map as a spatial information system placing spatial data, (location-based data about objects or phenomena), in correct relation to each other.

How Maps Represent Reality

• Cartographers select features or add invisible phenomenon based on the map's purpose and scale.

Map Use: Reading, Analysis, and Interpretation

• Map reading is determining what the map maker depicted, including identifying location or attribute.
• Map analysis detects spatial patterns on the map, noting any trends or directions.
• Map interpretation involves explaining these patterns to gain insights and make predictions or decisions.

What Maps Can Offer

• Maps can help answer questions about migration causes, visibility range, event locations, efficient routes, and disease outbreaks.

Medium of Display

• Maps can be displayed in various formats, including:
• Globes, which are 3D spheres and representations of the Earth
• Printed paper
• Desktop browsers
• Mobile phone screens
• Satellite imagery.
• Car navigation systems.
• 3D printers, which can produce topographic maps.

Map Elements and Symbols

• Due to the impossibility of labeling every feature, maps use map symbols and elements.
• These elements include titles, inset maps, symbols, scale bars, source information, north arrows, neat lines, and legends.

Maps are Useful for Answering Questions

• Maps can answer questions like "What is there?", "How big is it?", "How do I get there?", and "How does a disease spread?"
• Overlapping multiple layers on a map can reveal inter-relationships between spatial events

"Observe" and "Infer"

• Maps allow one to "observe" and "infer,"
• Processes by observing patterns through visualization.

Overlaying Maps

• Overlaying maps reveals spatial relationships and can provide insights or answers to questions.

Purposes of Maps

• Maps store geographical data/information
• Maps serve as mobility and navigation aids
• Maps visualize the invisible, (boundaries of countries and temperature)
• Maps recognize spatial distributions and potential relationships and help visualize processes.
• Maps summarize statistical data to detect patterns and trends for forecasting and decision-making.
• Maps stimulate spatial thinking about the placement of resources, climate, farming technology, natural disasters, and how they relate to each other

GIS Software

• Mapping or Geographic Information System (GIS) software (e.g., ArcGIS Pro and QGIS) provides tools for mapping and design.
• Cartographic rules are needed to make a map that can communicate with general users.
• A map's appearance and readability determine its usefulness.

Spatial Data

• Spatial data is recorded and displayed on a map
• Spatial data translates into a graphic representation that visually displays the location, distribution, and spatial relationship
• It includes spatial geographic features, invisible features, and phenomena.

What Spatial Data Is

• Geographic Data, Spatial Data, Geospatial data, and location data are often used interactively,
• Refer to any information about the location, shape, and relationships among geographic features.

Types of Spatial Data Models

• There are two types; Vector and Raster
• Vector data models use coordinates to store the shape of spatial data objects, like topographic maps or road networks.
• Raster data models use individual cells in a matrix or grid format to represent real-world entities, like satellite imagery, aerial photos, or scanned maps.

Vector Data Model Characteristics

• Features are represented by points, lines, or areas (polygons) defined by x-y coordinates.
• It organizes geometric objects and their spatial relationships into digital data files for computer access, interpretation, and processing.

Raster Data Model Characteristics

• Each location is represented by a cell (or pixel) organized into a matrix with rows and columns (a grid).
• The value may be a measurement like light intensity, numerical data (elevation, temperature), or a class of category (land use code or soil type).

Characteristics of Spatial Data

• Spatial data has:
• Geographic position (e.g., coordinates).
• Attributes (descriptive information).
• Spatial relationships (how objects are located in space relative to each other).
• Time (how the locations are changing over time).

Geographic Position

• Geographic position include geographic reference systems such as absolute position (coordinates) and relative position (location relative to another place).

Data Attributes

• Data describes characteristics of the spatial features with quantitative data (width, length, traffic volume)
• Data has qualitative data (road name, direction, categories)
• Attributes connect with the spatial feature, which is referred to as geometry

Spatial Relationship

• This illustrates how an object is located in space in relation to another object based on computed coordinates of spatial features

Time

• Historical data is used for time series analysis, like tracking population density changes.
• Historical maps and spatial data animate historical events, like the Imperial Japanese occupation of Hong Kong.

Sources of Geographic Data

• GIS data originates from digital resources classified as primary or secondary.
• Primary data comes from direct measurement (e.g., GPS).
• Secondary data is derived from existing sources, (e.g., old paper maps)

Open Data Sources

• Maps in Hong Kong are supplied by the Lands Department, HKSAR.
• Hong Kong Common Spatial Data Infrastructure, which provides free spatial data
• Data.gov.hk with data from different departments of Hong Kong Government
• Open Geo-Spatial Data in HK
• Esri China (Hong Kong) Limited,
• USGS (US-based datahub)