GPS-H

GPS·H Online Computation

GPS·H allows GPS users to convert their ellipsoidal heights (h) in either NAD83(CSRS) or ITRF/WGS84 to orthometric heights H (heights above mean sea level) by applying at each location a geoid height N derived from a geoid model (or Height Transformation).

The 3 heights: relationship of the ellipsoid to the geoid and topography with respect to GPS location. The orthometric height (large H) is equal to the ellipsoidal height from GPS (little h) minus the geoid height (N).

The 3 Heights

Larger image [JPEG, 48.2 kb, 697 X 393, notice]

Depending on the application, either a geoid model (CGG2010 is the latest) or the HT2.0 "Height Transformation" can be used. Several GPS and GIS software packages can also read geoid models to produce orthometric heights.

You can run GPS·H Online or download GPS·H software for standalone PC use.

Note: the online version currently can only apply the HT2.0 height transformation.  The GPS·H software download comes with HT2.0 as a default but it can read other geoid models.  The geoid models CGG2010 (the latest), CGG2005, CGG2000, GSD95 and GSD91 can all be downloaded here.