Valid Datum Specifications:
| DATUM ID | ELLIPSE | DEFINITION/COMMENTS |
| WGS84 | WGS84 | towgs84=0,0,0 |
| GGRS87 | GRS80 | towgs84=-199.87,74.79,246.62/Greek_Geodetic_Reference_System_1987 |
| NAD83 | GRS80 | towgs84=0,0,0/North_American_Datum_1983 |
| NAD27 | clrk66 | nadgrids=@conus,@alaska,@ntv2_0.gsb,@ntv1_can.dat/North_American_Datum_1927 |
| potsdam | bessel | towgs84=606.0,23.0,413.0/Potsdam Rauenberg 1950 DHDN |
| carthage | clark80 | towgs84=-263.0,6.0,431.0/Carthage 1934 Tunisia |
| hermannskogel | bessel | towgs84=653.0,-212.0,449.0/Hermannskogel |
| ire65 | mod_airy | towgs84=482.530,-130.596,564.557,-1.042,-0.214,-0.631,8.15/Ireland 1965 |
| nzgd49 | intl | towgs84=59.47,-5.04,187.44,0.47,-0.1,1.024,-4.5993/New Zealand Geodetic Datum 1949 |
| OSGB36 | airy | towgs84=446.448,-125.157,542.060,0.1502,0.2470,0.8421,-20.4894/Airy 1830 |