Product InformationWhy is the Altitude of a Meinberg GPS Receiver not Consistent?
The GPS altitude value refers to the altitude of the antenna position above the surface of the mean earth ellipsoid, not the height above the street.
Earth ellipsoids are described by a set of parameters called "geodetic datum". The standard geodetic datum used with GPS is called WGS84, which approximates the surface of the globe reasonably all over the world. Maps often use a different geodetic datum which approximates the form of the globe better than WGS84 for a given region where it shall be used, but worse for other regions of the world. In order to compare georaphic coordinates, both sets of coordinates must refer to the same geodetic datum.
Additionally, the altitude value of GPS receivers is the parameter which is the most inaccurate, compared to the accuracy of latitude, longitude, and time. This is a simply geometric issue due to the fact that, from the receiver's point of view, all usable satellites are "above" the antenna.
