Authoritative definitions of fundamental cartographic projections, geodetic reference datums, open vector data standards, and administrative boundary nomenclature. Maintained by Open Map Lab for researchers, teachers, and geospatial engineers.
A base outline map that delineates outer geopolitical boundaries or internal subdivisions with zero text labels, watermarks, or raster shading.
Serves as an unencumbered spatial canvas for classroom educational tests, choropleth thematic data coloring, route plotting, and custom graphic design overlays.
A mathematical model of the Earth’s oblate ellipsoidal shape combined with a network of reference control points used to define geographic coordinate systems.
WGS84 (World Geodetic System 1984) serves as the global standard for GPS satellite navigation, while NAD83 (North American Datum 1983) is the statutory standard for federal United States surveying.
A systematic mathematical transformation of angular spherical or ellipsoidal surface coordinates (latitude and longitude) onto a flat, two-dimensional Cartesian plane.
Because a curved spherical surface cannot be flattened without tearing or compression, all projections introduce geometric trade-offs between area, shape, distance, or direction.
A map projection engineered to preserve the exact relative proportional surface areas of all regions across the globe at the expense of local angular distortion.
Essential for thematic choropleth maps, demographic distributions, and geopolitical area comparisons (e.g., Albers Equal-Area Conic for the US, Equal Earth or Gall-Peters for global maps).
A map projection that preserves infinitesimal local angles and true compass bearings in every direction, maintaining recognizable local shapes while severely distorting regional areas toward the poles.
Standard for marine navigation, aviation charts, and regional topographic cadastral surveys (e.g., Mercator, Lambert Conformal Conic).
An XML-based, open standard vector graphics format that describes two-dimensional geometry using mathematical paths, bezier curves, polygon vertices, and styling attributes.
Unlike raster images (JPEG, PNG) that lose fidelity when scaled, SVG maps render with infinite optical resolution at any display size or 300+ DPI print scale, allowing individual administrative polygon paths to be styled with CSS.
An extension of GeoJSON that encodes geospatial geometry topologically, representing shared boundaries between adjacent polygons as shared mathematical arcs.
Eliminates redundant coordinate duplication between neighboring states or counties, reducing file sizes by up to 80% while completely preventing digital sliver gaps and boundary overlaps.
An open, text-based standard format for encoding geographic data structures including Points, LineStrings, Polygons, and MultiPolygons along with associated metadata properties.
Governed by IETF RFC 7946 using standard WGS84 geographic coordinates, GeoJSON is the universal interchange standard for web GIS mapping engines like MapLibre GL and Leaflet.
A thematic map in which predefined administrative geographic units (such as states, counties, or census tracts) are shaded or patterned in proportion to a measured statistical variable.
Used to visualize continuous statistical rates such as population density, median household income, per-capita sales tax rates, or voter turnout percentages.
The geometric center of mass of a two-dimensional polygon, calculated by computing the arithmetic mean position of all coordinate vertices along its boundary.
Crucial for automated label placement, proportional circle symbol anchoring, and point-in-polygon routing algorithms without visual clutter.
A worldwide legal instrument by which a creator waives all copyright, neighboring, and related rights in a work, dedicating it unconditionally to the public commons.
Enables educators, publishers, software developers, and commercial enterprises to download, modify, and commercialize cartographic vector files without licensing fees, attribution mandates, or paywalls.
A standardized, 5-digit numerical identification system established by the United States federal government to uniquely identify geographic and administrative entities.
The first two digits represent the state (e.g., 48 for Texas, 06 for California), while the last three digits uniquely distinguish individual counties (e.g., 48201 for Harris County, TX).
An administrative division in the United States that does not carry the formal legal title of "county" but is statistically and geographically recognized as functioning at the secondary administrative tier.
Includes Louisiana's 64 Parishes, Alaska's 19 organized Boroughs and 11 Census Areas, Virginia's 38 Independent Cities, Connecticut's 9 Planning Regions, and Puerto Rico's 78 Municipios.
A well-documented source of statistical bias in spatial analysis occurring when point-based socio-demographic phenomena are aggregated into arbitrary geographic boundary zones.
Changing the scale or spatial configuration of aggregation zones (e.g., gerrymandering or varying census tract sizes) can drastically shift statistical correlation results.
The precise outermost border or clipping frame of a map sheet that separates the cartographic image area from the surrounding page margin, graticule ticks, and legend metadata.
Establishes the visual boundary and ensures precise registration during professional printing and architectural document trimming.
