I am using ArcMap 10.7.

It comes down to needing to get my data into a local custom spatial reference system. I have not yet been able to project my data into it.

Desired coordinate system/spatial reference: Calgary_3TM_WGS_1984_W114

Full detail:

Projection: Transverse_Mercator
false_easting: 0.0
false_northing: 0.0
central_meridian: -114.0
scale_factor: 0.9999
latitude_of_origin: 0.0
Linear Unit: Meter (1.0)

Geographic Coordinate System: GCS_WGS_1984
Angular Unit: Degree (0.0174532925199433)
Prime Meridian: Greenwich (0.0)
Datum: D_WGS_1984
Spheroid: World_Geodetic_System_of_1984_GEM_10C
    Semimajor Axis: 6378137.0
    Semiminor Axis: 6356752.314245179
    Inverse Flattening: 298.257223563

So far I have tried a number of the datum transformations included in ArcGIS for NAD83 -> WGS84 but none have worked, resulting in errors such as 'geographic transformation not valid'.

To create a new custom geographic transformation I was never taught, and looking online has extremely little information on doing so, and the printed material simply explains what geographic transformations are and no further. I have so far only found a single video, which brings up the issue of the 'method' of the transformation. I haven't been able to find anything from Esri on the subject (but perhaps I am not looking in the right place).

What am I doing incorrectly, or what must I do in moving forward on this?

1 Answer 1


It turns out that the Calgary 3tm projection I was trying to use with the "World_Geodetic_System_of_1984_GEM_10C" Spheroid was actually a variant of the official/proper one. I tried another that used another spheroid, it was successfully associated with the correct geographic transformation (WGS_1984_(ITRF00)_To_NAD_1983) in ArcGIS.

I have no idea why it was using GEM 10C based on what I read about it ( factors in gravity potential and a few other things).

  • It's the spheroid definition. That doesn't match what Esri uses for WGS 84.
    – mkennedy
    Commented Jul 12, 2020 at 2:42

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