projection name issue GM vs ArcGIS

Amasaeda

Hi, I have a issue with GeoTiffs written out with GM. For custom projections (Lambert with specific parameters), ArcGIS shows the projection name of the GeoTiff as "GCS_WGS_1984" but all other parameters are correct. Has anyone encountered this and is there any way to work around it? Thanks!

bmg_bob

Hi,

What version of Global Mapper are you using?

Is your data located correctly in ArcGIS despite the incorrect projection name?  That would indicate that, even though the name is wrong, ArcGIS is using the correct definition.

Another option is to use the "Generate PRJ File" option when exporting your GeoTIFF from Global Mapper.  ArcGIS might then use the PRJ instead of the definitions in the GeoTIFF file, and that might work better.  If that doesn't work, please post the PRJ here and we can take a look.

sandyhannum

I am no expert on projections, but isn't GCS_WGS_1984 a datum (Geographic Coordinate System), and Lambert is a type projection, so having both items listed could be correct? I have some Lambert projected files where the datum is GCS_North_American_1983. This question made me curious.

bmg_bob

sandyhannum said:

I am no expert on projections, but isn't GCS_WGS_1984 a datum (Geographic Coordinate System), and Lambert is a type projection, so having both items listed could be correct? I have some Lambert projected files where the datum is GCS_North_American_1983. This question made me curious.

You are correct.  The original question suggests that ArcGIS is using the datum name as the name of the projected coordinate system.  Typically, in this case, ArcGIS would show both a projected system (Lambert) and a Geographic system (WGS84).  Since the @Amasaedais using a custom system, it is possible that the name got mixed up somehow.

Amasaeda

Hi, I'm on GM v17.0 Everything is perfectly located in ArcGIS, all projection parameters are correct, only the name is wrong. Unfortunately, generating the prj file doesn't help, ArcGIS still reads "GCS_WGS_1984". Unfortunately, I can't send the .prj file along. But I can paste below as string: PROJCS["Lambert_Conformal_Conic",GEOGCS["GCS_WGS_1984",DATUM["D_WGS84",SPHEROID["WGS84",6378137,298.257223563]],PRIMEM["Greenwich",0],UNIT["Degree",0.017453292519943295]],PROJECTION["Lambert_Conformal_Conic"],PARAMETER["scale_factor",1],PARAMETER["standard_parallel_1",65.33333333330022],PARAMETER["standard_parallel_2",70.66666666669978],PARAMETER["central_meridian",22.5],PARAMETER["latitude_of_origin",0],PARAMETER["false_easting",0],PARAMETER["false_northing",0],UNIT["Meter",1]] Thanks for your help

Amasaeda

Quite right, In ArcGIS, I get "GCS_WGS_1984" in the Spatial Reference field (which I assume means Geographic coordinate system on WGS84 Datum, so the "projection", not the Datum). In the Datum field, I see correctly "D_WGS_1984"

bmg_bob

I exported a GeoTIFF using your custom projection (loaded from your PRJ string), creating a PRJ during the export.  My GeoTIF loaded into ArcMap 9.3.1, and on the Data Frame Properties I see Projection: Lambert_Conformal_Conic, and the Geographic system is GCS_WGS_1984, which looks correct.

Here is something to try:
- Load your original data into GM.
- Change the Projection to your custom projection using the PRJ file (Load from File... on the Projection tab, Configuration window)
- Export your GeoTIFF
- Load into ArcGIS

Those are the steps that I used.  It will be interesting to see if that works for you.

Amasaeda

thanks for the hints. I did the same. no changes, I still get "GCS_WGS_1984" as projection in ArcGIS 10.3.1 Can you send your file so I can open here and see if it's the same in my version of ArcGIS?

bmg_bob

Here you go...

bmg_bob

One more thing...if you haven't already done so, you should get the latest release of Global Mapper 17.1.

Amasaeda

Hi Bob, thanks for the file. It shows as "GCS_WGS_1984" for projection in ArcGIS 10.3.1. If you have no more idea, I'll check with esri. Thanks for all the help