map projection


GIS Data

This overlay showing WGS 84 Ellipsoid Mercator in Blue and the Spherical Web Mercator in Red WGS 84 highlights the spatial inaccuracies of the latter projection.This overlay showing WGS 84 Ellipsoid Mercator in Blue and the Spherical Web Mercator in Red WGS 84 highlights the spatial inaccuracies of the latter projection.

National Geospatial-Intelligence Agency’s Web Mercator Advisory Notice

The National Geospatial-Intelligence Agency (NGA) has an advisory notice posted on its site warning about errors users of the popular Web Mercator projection stating, “the use of Web Mercator and other non-WGS 84 spatial reference systems may cause geo-location / geo-coordinate errors up to 40,000 meters.”