OCTO and agency stakeholders with custom web map applications select spatial data coordinate systems that best meets requirements for its intended use.

Maryland State Plane NAD 83 (meters)

The data stored in the District’s internal enterprise geodatabase, managed by OCTO, are projected in the Maryland State Plane coordinate system of the American Datum of 1983 (NAD 83). This local, and more focused, projection supports better analysis and data maintenance for projects like the Master Address Repository and Vector Property Mapping. Shapefile data projected in MD State Plane NAD 83 are available upon request at [email protected]. Also, some ArcGIS Server Map Services are MD State Plane; those that are not labeled WebMercator.

WGS 84 Web Mercator

The majority of public facing web apps use the WGS 84 Web Mercator as its projected coordinate system. The District re-projects its data to best integrate with world-wide industry platforms such as Google Maps, Mapbox and Esri. The following include data that are provided in WGS 84 Web Mercator,

• DC Atlas Plus
• Open Data DC APIs and File Downloads
• DC Government’s ArcGIS Online Organization
• ArcGIS Server Map Services (labeled _WebMercator)
• Map Gallery