GIS TerminologyPlain-language definitions for common geospatial terms
Shapefile
Data Format
A popular geospatial vector data format developed by Esri. Despite its name, a shapefile is actually a collection of files (.shp, .shx, .dbf, and others) that together store geometry and attribute data.
ExampleWhen downloading parcel boundaries from a county GIS portal, you'll often receive a .zip containing multiple shapefile components.
GeoJSON
Data Format
A lightweight, text-based format for encoding geographic features. Based on JSON, it's easy to read and widely supported by web mapping libraries.
ExampleWeb developers often prefer GeoJSON for mapping applications because it works natively with JavaScript and APIs like Mapbox or Leaflet.
WGS 84 (EPSG:4326)
Coordinate System
The most common geographic coordinate system, using latitude and longitude in degrees. It's the standard for GPS and most web mapping.
ExampleWhen you see coordinates like "37.7749, -122.4194" (San Francisco), that's WGS 84.
Web Mercator (EPSG:3857)
Coordinate System
A projected coordinate system used by Google Maps, Bing, and most web mapping platforms. Coordinates are in meters, not degrees.
ExampleIf you're building a web map with tiles from OpenStreetMap, your data needs to be in Web Mercator to align properly.
NAD83
Coordinate System
North American Datum 1983 — a reference system used for mapping in North America. Often paired with State Plane zones for high-accuracy local mapping.
ExampleUS government agencies like USGS and state DOTs typically publish data in NAD83.
Feature Service
Web Service
A web service that provides access to vector data (points, lines, polygons) with the ability to query, edit, and analyze features.
ExampleArcGIS Hub datasets often provide Feature Service URLs that you can connect to directly in QGIS or ArcGIS Pro.
Tile Service / WMTS
Web Service
A web service that delivers pre-rendered map images (tiles) at various zoom levels. Fast to display but not queryable.
ExampleBasemaps like satellite imagery or street maps are typically served as tile layers for performance.
Raster Data
Data Type
Grid-based data where each cell (pixel) contains a value. Used for continuous data like elevation, temperature, or satellite imagery.
ExampleA Digital Elevation Model (DEM) is raster data where each pixel represents the ground elevation at that location.
Vector Data
Data Type
Data represented as points, lines, or polygons with associated attributes. Best for discrete features like roads, buildings, or boundaries.
ExampleCensus tract boundaries are vector data — each polygon has attributes like population and median income.
Metadata
Concept
Data about data — information describing a dataset's source, date, accuracy, projection, and how it should be used.
ExampleGood metadata tells you when data was last updated, who created it, and what coordinate system it uses.
Extent / Bounding Box
Concept
The geographic area covered by a dataset, defined by minimum and maximum coordinates (west, south, east, north).
ExampleBefore downloading a large dataset, check its extent to make sure it covers your area of interest.
Attribute Table
Concept
A table of data associated with geographic features. Each row represents a feature; columns contain properties like name, type, or measurements.
ExampleA roads layer might have attributes for road name, speed limit, surface type, and number of lanes.
More terms coming soonWe're continuously adding definitions based on what users search for and ask about.
GIS Terminology | FindGeoData Academy | FindGeoData