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Calculate the geoid separation for any point.

Works out the geoid separation for any latitude or longitude. A geoid is the name for the undulating shape that the Earth would assume if it were all measured at mean sea level. The geoid separation is the distance between a point on this surface and the point on the ideal spheroid for the Earth's surface.

The value is computed by bilinearly interpolating a 2D table of values sampled at a resolution of 10x10 deg. This table is defined in TsTileSpecGen.h. Values of lat/long given in the range -90..+90, and -180..+180 respectively. (N.B. you can also specify longitude in the range 0..360, where 0 is still Greenwich Meridian, but 180..360 maps to -180..0. It is not obvious that a 0..180 mapping makes sense for latitude so we do not support this.)

If you have UTM coordinates, then you can convert them to lat/long using the tsmUTMToGeo function.