I am trying to draw a census tract on a Google map. It looks like Google Maps lets you draw polygons using longitude and latitude coordinates. However, the data that I have is not longitudes/latitudes.

The specific dataset I have looks like this. The "spatial reference" for this data is 3857. But after looking up this spatial reference on this page, I still am not quite sure how to go about drawing the shape to the map using longitudes/latitudes.

I assume that this sort of thing can be done with GIS software or command line tools, but I am more interested in code libraries or APIs that could make this possible. Also, if anyone knows of a better source of census tract shape data which is more compatible with Google Maps, that would be great too.

  • Use epsg 3857 WGS_1984_Web_Mercator_Auxiliary_Sphere on your outSR (Spatial reference output)
    – Mapperz
    Commented Oct 28, 2013 at 1:59

1 Answer 1


Welcome to the GIS StackExchange. The library you are looking for is Proj4, originally written in C/C++. You can also find Proj4 APIs in other languages:


  • Thanks. I will mark this answer as correct because it answers my general question, although Mapperz' comment is more practical in my particular situation. Commented Oct 30, 2013 at 17:18

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