Lectures and exercises prepared for the Riyadh geoid workshop.

Lecture 0.1
Lecture 1.1
Lecture 1.2
Lecture 1.3
Lecture 1.4
Lecture 1.5
Lecture 2.1
Lecture 2.2
Lecture 2.2a
Lecture 2.4
Lecture 3.1
Lecture 3.2
Lecture 3.5
Lecture 3.6
Lecture 4.1
Lecture 4.2
Lecture 4.3
Lecture 4.4
Exercise 1.5
Exercise 2.3

Data and job-files for geoid computation.

Free-air gravity
Free-air gravity - DIR3.
Free-air gravity - DIR3 -tc.
Free-air gravity - EGM08 output.
Program to convert SRDTM30 xyz file to GRAVSOFT grid-file .
Converted SRDTM30 xyz file to GRAVSOFT grid-file .
Output file to create reference grid
reference grid
Output to compute and subtract TC effects
Result of subtracting TC effects
-- average no of prisms/exact formulas pr station: 1840 83
--- difference given - dtm inferred station heights:
mean stddev min max: -10. 50. -689. 571.
--- statistics of computed effects, no of points: 2196
mean stddev min max
-3.53 16.52 -105.01 112.16
--- statistics of original values in statfile:
-2.91 33.89 -111.91 183.85
--- difference output on file:
0.63 24.59 -95.70 98.69
It is remarkable how the mean value has become nearly zero and the large tops have been reduced !
Original files in /home/gfy-1/cct and /home/gfy-gut/cct/cct1/dgravsoft.
Tests with EGM2008 gives further lowering of the gravity anomaly (residual) variance..
Free-air gravity - EGM08 output.
In this case a reference DTM with less smoothing was used, srtm5.
See output from TC.
The difference file was used to estimate an empirical covariance function using empcov.
Covfit16 was then used to fit an analytic model, which subsequently was used to estimate height anomalies at zero elevation, The smallest error is only 0.03 m close to the gravity measurements used.
See Plot of height anomalies,
See Plot of height anomaly error estimates.

Summary of KSA quasi-geoid computation.

Sequence of computation steps using least-squares collocation.
Last update: 2013-12-31.