Glossary
Attribute Data
Non-spatial information that describes the characteristics or properties of geographic features, linked to their spatial location.
Example:
For a map of schools, the attribute data might include the number of students, average test scores, or school district boundaries.
Census Data
Demographic and socioeconomic information collected by governments about the characteristics of their populations, typically through a periodic survey.
Example:
Governments use census data to determine the allocation of political representation and funding for public services like schools and hospitals.
Digital Elevation Models (DEMs)
Gridded spatial data that represents the bare-earth surface topography, showing elevation values for each cell.
Example:
Hydrologists use Digital Elevation Models to determine watershed boundaries and predict water flow paths.
Distortion (in maps)
The inevitable alteration of shape, area, distance, or direction that occurs when projecting a 3D sphere onto a 2D surface.
Example:
The large size of Greenland on a Mercator map is a classic example of area distortion.
GIS (Geographic Information System)
A powerful computer system designed for capturing, storing, analyzing, managing, and presenting all types of geographically referenced data.
Example:
Urban planners use GIS to analyze population density, identify suitable locations for new parks, and manage city infrastructure.
GPS (Global Positioning System)
A satellite-based navigation system that provides precise location and time information anywhere on Earth with a receiver.
Example:
Your smartphone uses GPS to pinpoint your current location and provide turn-by-turn directions while driving.
GPS Coordinates
Numerical values, typically latitude and longitude, that precisely define a location on the Earth's surface.
Example:
Sharing your GPS coordinates allows someone to find your exact position on a map.
Gall-Peters Projection
An equal-area map projection that accurately preserves the relative sizes of landmasses but distorts their shapes, particularly near the equator and poles.
Example:
Advocates for representing global inequalities often prefer the Gall-Peters Projection to accurately show the true land area of developing nations.
Geometric Data
A type of spatial information that describes the shape and size of features using points, lines, or polygons.
Example:
A city's zoning map uses geometric data where individual parcels are represented as polygons and streets as lines.
Geospatial Databases
Organized collections of spatial data and associated attribute data, designed for efficient storage, retrieval, and analysis.
Example:
A city's planning department maintains a geospatial database containing information on all properties, zoning regulations, and utility lines.
Imagery (Spatial Information)
Digital images of the Earth's surface captured from satellites or aircraft, providing visual information about land cover and features.
Example:
Analyzing recent satellite imagery can reveal the extent of urban sprawl around a major metropolitan area.
Large Scale
A map scale that shows a small geographic area with a high level of detail, often used for city maps or neighborhood plans.
Example:
A large scale map of a university campus would show individual buildings, pathways, and even parking lots.
Map Projections
Methods used to represent the 3D surface of the Earth on a 2D flat map, which always results in some form of distortion.
Example:
Choosing the right map projection is crucial; for instance, a cartographer designing a world map for a textbook might opt for one that minimizes overall distortion.
Map Scale
The ratio between a distance on a map and the corresponding distance on the ground, indicating the level of detail shown.
Example:
Understanding the map scale is vital; a map with a scale of 1:24,000 shows much more detail than one with a scale of 1:1,000,000.
Maps
Representations of the Earth's surface that are essential for understanding spatial relationships and visualizing geographic data.
Example:
An urban planner might use various maps to analyze population distribution and plan new public transportation routes.
Mercator Projection
A cylindrical map projection that preserves shape and direction, making it useful for navigation, but significantly distorts area, especially near the poles.
Example:
Sailors historically favored the Mercator Projection because it allowed them to plot a straight course with true compass bearings.
Network Data
Spatial information that represents connections and relationships between features, such as roads, rivers, or utility lines.
Example:
A delivery company uses network data to optimize routes for its trucks, considering road segments and intersections.
Raster Data
A type of spatial data that represents geographic features as a grid of cells or pixels, often used for continuous phenomena like elevation or temperature.
Example:
A satellite image or a digital elevation model is stored as raster data, where each pixel has a specific value.
Reference Maps
Maps that show the locations of places and geographic features, primarily for general navigation and orientation.
Example:
When planning a road trip across the United States, you would likely consult a reference map to see state borders and major highways.
Robinson Projection
A compromise map projection that attempts to minimize overall distortion across all properties (shape, area, distance, direction), making it suitable for general world maps.
Example:
Many atlases and textbooks use the Robinson Projection because it offers a visually balanced representation of the world, even though it doesn't perfectly preserve any single property.
Satellite Imagery (Spatial Data)
Images of the Earth's surface captured by satellites, providing visual data for various analyses like land cover change or urban growth.
Example:
Monitoring the expansion of agricultural fields into rainforests often relies on recent satellite imagery.
Small Scale
A map scale that shows a large geographic area with less detail, typically used for regional, national, or world maps.
Example:
A world atlas contains many small scale maps, allowing you to see entire continents or oceans at once.
Spatial Data
Any data that has a geographic component, meaning it can be mapped or located on the Earth's surface.
Example:
Information about the location of hospitals, rivers, or voting districts are all examples of spatial data.
Spatial Information
Data that describes the location, shape, and relationships of geographic features on Earth, forming the basis for maps and GIS.
Example:
Collecting spatial information about deforestation rates helps environmental scientists track changes in forest cover over time.
Street Maps (Spatial Data)
Geospatial data representing the layout of streets, roads, and sometimes other transportation infrastructure within an area.
Example:
Navigation apps rely heavily on up-to-date street maps to provide accurate directions and traffic information.
Temporal Data
Spatial information that includes a time component, showing how geographic phenomena change or evolve over a period.
Example:
A geographer studying climate change might use temporal data to visualize the retreat of glaciers over several decades.
Thematic Maps
Maps that tell a specific story about a place by showing the distribution, pattern, or variation of a particular phenomenon.
Example:
A geographer studying climate change might create a thematic map showing the average annual temperature changes across different continents over the last century.
Topographic Data
Spatial information that represents the elevation and landforms of the Earth's surface, often depicted using contour lines.
Example:
Hikers often consult maps with topographic data to understand the steepness of trails and identify peaks or valleys.
Trilateration
The process used by GPS receivers to determine a precise location by calculating distances from at least three satellites.
Example:
By measuring the time it takes for signals to arrive from multiple satellites, a GPS receiver performs trilateration to find its exact coordinates.
Vector Data
A type of spatial data that represents geographic features as discrete points, lines, or polygons, ideal for representing distinct boundaries or locations.
Example:
A map showing country borders, rivers, and cities would typically use vector data.