EPSG
http://earth-info.nga.mil/GandG/wgs84/gravitymod/egm2008/egm08_wgs84.html
2015-11-25
Geodesy.
Replaces EGM96 geoid (datum code 5171). See transformation codes 3858 and 3859 for 2.5x2.5 and 1x1 arc minute geoid undulation grid files derived from the spherical harmonic coefficients.
Definition: JSON
{ "$schema": "https://proj.org/schemas/v0.7/projjson.schema.json", "type": "VerticalReferenceFrame", "name": "EGM2008 geoid", "scope": "Geodesy.", "area": "World.", "bbox": { "south_latitude": -90, "west_longitude": -180, "north_latitude": 90, "east_longitude": 180 }, "id": { "authority": "EPSG", "code": 1027 } }