### 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.