Geoscience Reference
In-Depth Information
_
_
A
B
l
2
B
l
1
earth's surface
H
B
-H
A
A
H
B
H
A
h
B
h
A
geoid
N
A
N
B
ellipsoid
Fig. 4.6. GPS leveling
With GPS leveling,
δh
AB
is obtained, so that with a known geoid, i.e., known
δN
AB
, the orthometric height difference
δH
AB
may be computed accord-
ing to (4-75). This is a tremendous advantage since otherwise the classical
leveling together with gravity measurements is required to determine the
orthometric height difference, see Eqs. (4-40) and (4-46).
Note that only the difference of the geoidal undulations impacts the
result.
