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impact of the atmosphere on the satellite measurements is examined. We present a
descriptions of the oceanic mass response to overlying atmospheric pressure and of
the models used for de-aliasing of atmospheric effects.
1 Theory of the Gravity Field
The purpose of this section is to introduce the fundamentals of the potential theory,
i.e. gravity acceleration and gravity potential with their most important relationships.
Also an introduction to spherical harmonics is given. The following information can
be found in more detail in Hofmann-Wellenhof and Moritz ( 2005 ) and Torge ( 1989 ).
1.1 Gravity Potential and Gravity Acceleration
According to Newton's law of gravitation, two point masses m 1 and m 2 separated by
a distance r attract each other with a force
G m 1 m 2
r 2
F
=
r 0 ,
(1)
10 11 m 3 kg 1 s 2 is the gravitational constant (Hofmann-
Wellenhof andMoritz 2005 ). By setting one mass to unity and denoting the attracting
mass with m , we express the force F exerted by the mass m on a unit mass at location
P and distance r as
where G
=
6
.
6742
×
G m
F
=
r 2 r 0 .
(2)
This representation of the gravitational attraction can be simplified if instead of
the vector quantity acceleration F the scalar quantity of the potential V is used.
Especially when looking at the attraction of point systems and solid bodies as it is
done in geodesy, calculations can be simplified greatly.
Following Torge ( 1989 )
rot F
=
0
,
(3)
and therefore a corresponding potential V for the gravitational field F exists so that
=
,
F
grad V
(4)
where
Gm
r .
V
=
(5)
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