Thanks, this is NOT the standard Web Mercator projection. I am aware of EPSG:90013 and EPSG:3857. This projection is used with HYCOM data that I have extracted into geotif files so that I can accurately project that onto EPSG:3857. It took some fiddling with the values to get to overlay visually correctly. HYCOM data is weird in that it uses two different projections based on if the data is above or below some latitude.

On 4/13/2024 4:19 AM, Javier Jimenez Shaw via gdal-dev wrote:
If what you need is really EPSG:3857, yes, use it.

However I have seen strange parameters on your projection. The radius of the sphere is the "average" 3671 km, and you set a false easting and northing of just 4.4 km. Is that trying to correct the radius of the sphere? I do not know why you need that.

Bas, are they really equivalent?

In proj you can convert to WKT1 (see that I added +type=crs):

projinfo "+proj=merc +a=6371001 +b=6371001 +lat_ts=0.0 +lon_0=0.0 +x_0=-4448 +y_0=-4448 +k=1.0 +units=m +over +nadgrids=@null +no_defs  +type=crs" -o wkt1_gdal

Ok I get this adding by +type=crs but how do I add it to the proj database so I can access it referencing it by something like EPSG:90014?

Thanks,
  -Steve

On Sat, 13 Apr 2024 at 06:17, Sebastiaan Couwenberg via gdal-dev <gdal-dev@lists.osgeo.org> wrote:

    On 4/12/24 11:24 PM, Stephen Woodbridge via gdal-dev wrote:
    > and was able to access it in gdal, mapserver, postgis, etc with
    > "EPSG:900914"

    I used to do that too, but switched to EPSG:3857 its non-deprecated
    equivalent. I would recommend that instead of trying to keep using a
    non-standard projection.

    Kind Regards,

    Bas

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