ChartTiff Web Mercator

Web Mercator Projection

Web Mercator, Google Web Mercator, Spherical Mercator, WGS 84 Web Mercator or WGS 84/Pseudo-Mercator is a variant of the Mercator projection and is the de facto standard for Web mapping applications. It rose to prominence when used in the first Google Maps in 2005.

Wikipedia has an on-line description of this projection at:

                https://en.wikipedia.org/wiki/Web_Mercator

WEB Mercator Projection uses EPSG:3857.

For GeoTIFF formats, the GeoTIFF record PCSCitationGeoKey
contains the following string for ESRI applications:

   ESRI PE String =
         PROJCS["WGS_1984_Web_Mercator_Auxiliary_Sphere",
   GEOGCS["GCS_WGS_1984",
   DATUM["D_WGS_1984",
   SPHEROID["WGS_1984",6378137,298.257223560493]],
   PRIMEM["Greenwich",0],
   UNIT["Degree",0.017453292519943295]],
   PROJECTION["Mercator"]
   PARAMETER["central_meridian",0],
   PARAMETER["standard_parallel_1",0],
   PARAMETER["false_easting",0],
   PARAMETER["false_northing",0],
   PARAMETER["Auxiliary_Sphere_Type",0],
   UNIT["Meter",1]]

   which is a copy of the .prj file created by ChartTiff
          for each file of WEB Mercator Projection.

For GeoTIFF formats, the GeoTIFF record GTCitationGeoKey contains the following string:

   PCS Name = WGS_1984_Web_Mercator_Auxiliary_Sphere

Some Elevation data file formats do not support WEB Mercator Projection, including:

   USGS DEM
   PLS-CADD XYZ File Format
   C Tech File Format