Does anyone know of a program that will interpolate geoid heights from the NGA EGM08 model using a batch file as input (similar to NGS intg.exe)? I found some sites on the web that will do a single point interpolation, but not one that will accept a file of points. Geolab (least squares program) will do the interpolation for points in an adjustment, but I want to create a dem to make a contour map and to compare against geoid18, etc.?ÿ
I found exactly what I needed...
http://icgem.gfz-potsdam.de/calcgrid
Not only will it compute from a user supplied file, it will also create a gridded file. Thanks to Dan Roman for pointing me to this site.?ÿ
And I note that the latest model is XGM2019e_2159, which I have read is very close to the upcoming EGM2020.?ÿ
I would definitely NOT use any of the NGS geoid models named GEOID## (where ## is the model??s year) as they are intended to combine North American Datum of 1983 (NAD83) ellipsoid heights (h) and the ellipsoid-to-geoid separation (N) to derive a North American Vertical Datum of 1988 (NAVD88) compatible orthometric height (H).?ÿ
See the NGS geoid page for the areas where the model can be used. BTW, Canada does not use NAVD88.
Either your agency/company/clients should specify what datum your work should be performed in. If it is WGS84 you might want to use this site??s search function to understand the various versions of this datum and its relationship to the International Terrestrial Reference Frame (ITRF) which has its own set of versions. It is a big bookkeeping effort.
The National Geospatial-Intelligence Agency site is:
https://earth-info.nga.mil/ ?ÿ
The NGA has an on-line tool to compute Geoid heights using its EGM.?ÿ
https://earth-info.nga.mil/index.php?dir=wgs84&action=egm96-geoid-calc