I found the following in http://help.arcgis.com/en/arcgisserver/10.0/apis/rest/index.html?pcs.html. The definition DATUM are mixed up between 102100 (3857) and 102113, since DATUM for 102100 should be using a sphere vs. 102113 should be using pancake. (the same thing happens for 3857). 3785 is gone from the list. If you look at the DATUM section, 102100 is using a pancake but 102113 is using sphere. Can you clarify? 102100 WGS_1984_Web_Mercator_Auxiliary_Sphere PROJCS["WGS_1984_Web_Mercator_Auxiliary_Sphere",GEOGCS["GCS_WGS_1984",DATUM["D_WGS_1984",SPHEROID["WGS_1984",6378137.0,298.257223563]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],PROJECTION["Mercator_Auxiliary_Sphere"],PARAMETER["False_Easting",0.0],PARAMETER["False_Northing",0.0],PARAMETER["Central_Meridian",0.0],PARAMETER["Standard_Parallel_1",0.0],PARAMETER["Auxiliary_Sphere_Type",0.0],UNIT["Meter",1.0]] 102113 WGS_1984_Web_Mercator PROJCS["WGS_1984_Web_Mercator",GEOGCS["GCS_WGS_1984_Major_Auxiliary_Sphere",DATUM["D_WGS_1984_Major_Auxiliary_Sphere",SPHEROID["WGS_1984_Major_Auxiliary_Sphere",6378137.0,0.0]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],PROJECTION["Mercator"],PARAMETER["False_Easting",0.0],PARAMETER["False_Northing",0.0],PARAMETER["Central_Meridian",0.0],PARAMETER["Standard_Parallel_1",0.0],UNIT["Meter",1.0]]
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