Contribution to IAG

Joint Study Group JSG0.3 (2011-2015)



Numerical comparisons between different approaches for regional gravity field modelling.

For regional gravity anomaly prediction in this study, two methods are used, one of them being Least-Squares Collocation (LSC) (developed by C. C. Tscherning, 1974) and the other the Reduced Point Mass (RPM) method (developed by Herceg, 2012).

Both methods show good agreement in prediction of the gravity anomaly residuals. Compared to the LSC method, the RPM method needs less time for calculation since LSC number of equations solved depends on the number of observations. When using RPM number of equations is dependent on the number of gridded point masses.



Prediction of T from GOCE Tzz gradient anomaly

(contribution up to spherical harmonic d/o 36 is removed):

Europe


Observations

Collocation

Diff (Col-Obs)

RPM

Diff (RPM-Obs)

Mean

-0.1141

0.1454

-0.2594

-0.7152

0.6011

St. Dev.

32.5489

31.4413

6.0328

31.4973

5.7783

Pacific


Observations

Collocation

Diff (Col-Obs)

RPM

Diff (RPM-Obs)

Mean

4.6159

4.80

-0.18

5.3564

-0.7405

St. Dev.

49.0739

48.52

6.66

48.4749

6.9177


Prediction of Tr from GOCE Tzz gradient anomaly

(contribution up to spherical harmonic d/o 36 is removed):

Europe


Observations

Collocation

Diff (Col-Obs)

RPM

Diff (RPM-Obs)

Mean

3.5638

2.29

1.27

2.4206

1.1431

St. Dev.

49.1310

37.10

29.44

38.6243

29.0696

Pacific


Observations

Collocation

Diff (Col-Obs)

RPM

Diff (RPM-Obs)

Mean

-2.2160

-3.60

1.39

-3.7367

1.5207

St. Dev.

65.2483

52.66

38.24

54.6542

39.5912


Prediction of T from terrestrial Tr

(contribution up to spherical harmonic d/o 240 is removed):

Europe


Observations

Collocation

Diff (Col-Obs)

RPM

Diff (RPM-Obs)

Mean

-0.0120

0.02

-0.03

-0.0799

0.0679

St. Dev.

4.0806

4.19

0.82

3.8173

1.4415

Pacific


Observations

Collocation

Diff (Col-Obs)

RPM

Diff (RPM-Obs)

Mean

-0.1273

-0.0715

-0.0557

0.2765

-0.4038

St. Dev.

4.8176

4.7864

0.2439

3.7575

2.9365


Prediction of T from airborne Tr (Corsica)

(contribution up to spherical harmonic d/o 240 is removed):

Europe ( Corsica)


Observations

RPM

Diff (RPM-Obs)

Mean

-0.0953

-0.5383

0.4429

St. Dev.

3.5330

2.9636

1.9740