KSA geoid preparation

LSC computation with data selected in 0.02 d dataa cells.

Error estimates.
Scaled error estimates.
Differens wrt FFT..

Comparisons sea-gravity with gravity model

Differences (mgal).

Comparison with ARAMCO GPS/levelling.


Comparison fft - lsc (using 0.01 d data) in 4 areas.

Plots of diferences and gravity stations.
NW area.
NE area.
SW area.
SE area.
Note that the differences are only large where there are no or little data.

Error estimation with airborne gravity added.

Using LSC with reduced data close to 0.025 deg. grid points (82569) error estimates of a (quasi) geoid was computed, see Figure
The errors are largest where there are no or sparse data or where the gravity variation is larger than the one used in the covariance modelling.
Grids of Gravity anomalies were generated at 2500 m altitude, covering an area bounded by 25 deg to 28 deg in latitude and 36 deg to 43 in longitude. The spacing in longitude was in all cases 0.05 deg. In latitude the spacing was 0.2, 0.25, 0.5 and 1.0 deg, respectively. File names are ksa_airborneX.XX.dat
All error estimates are in the area bounded by 24.0 29.0 35.0 44.0 in a 0.2 deg grid (at zero altitude) for all 4 examples. The computation is quite easy, since the 82400 first reduced equations are re-used.
The results using a smooth field can be seen from
No airborne .
0.2 deg. spaced .
0.25 deg. spaced .
0.5 deg. spaced .
1.0 deg. spaced .
The calculations were then repeated corresponding to the montaneous NE area at an altitude of 3.5 km. A new covariance model was determined.
No airborne .
0.1 deg. spaced .
0.1 deg. spaced with sea-gravity (5 mgal error assumed) .
0.2 deg. spaced .
0.25 deg. spaced .
0.5 deg. spaced .
1.0 deg. spaced .

Sea gravity files.

gravsoft format
geodas header
geodas format
Last update 2014-08-28.