Information on the Swiss geoid model CHGeo1998
by Urs Marti, December 2023

CHGeo98 was computed by swisstopo in 1998.
It was the official geoid model in Switzerland and Liechtenstein from 1998 to 2004.
It is a hybrid solution of deflections of the vertical, gravity and  GNSS-Levelling.
The solution is relative to ETRS89 (GRS80-Ellipsoid) with a resolution of 30".
The format of the original files is "ESRI ASCII grid" (.agr)

There are several variants of the model, which are shortly described here:
CHGeo98: Geoid model, compatible with Swiss orthometric heights LHN95 (preliminary version)
CHQua98_EF.agr: Quasigeoid model compatible with EVRF2000 (shifted by 10.31 cm from Swiss normal heights)
