Specifications

70 Z-Family Technical Reference Manual
Elevation Modeling
In addition to the ability to compute and output geodetic and cartesian coordinates in
different systems, the receiver can compute and output elevations in different
systems.
By default, the receiver computes and outputs ellipsoidal heights. In some messages,
the geoid separation is included, computed from the internal global model, relative to
WGS-84. To set the receiver to compute and output orthometric heights, use the
$PASHS,HGT,GEO command. Once this command is set, the receiver will output
orthometric heights using the internal global geoid model. Be aware that the internal
geoid model used in this calculation is very coarse. Orthometric heights derived from
using this model could be in error by a meter or more.
If separation is included in the message, this will be calculated by adding the difference between
WGS-84 and a user or pre-defined datum, to the WGS-84 based geoid separation. An exception to
this is the GGA message which ONLY outputs WGS-84 based geoid heights and separation, as per
NMEA specifications.
Figure 5.6: Lambert Conformal Conic