File: h:\cctwp\slice4.3.doc, 28 sep. 2001.

 

Slice 3: Input to Task 3. (with reference to Slice 2, structure, status and critical items).).

 

A. External calibration.

S3.1 Development sequence

S3.1.1 Inventory

 

SELECT: program to extract data in a region or conversion to GRAVSOFT format.

GEOCOL: subtraction of the contribution from an a-priori model. Data may be given in the specified satellite oriented frame. Program may be used for upward continuation of the ground data.

Calibration parameters (bias+tilt) and their errors may be estimated

TC: calculation and subtraction of topographic effects from ground and satellite data.

EMPCOV: estimation of empirical covariance function (from ground or satellite data)

COVFIT: analytic modeling of empirical covariance function.

 

All the programs have simple ASCII-based interfaces using the GRAVSOFT standards.

 

S3.1.2 Software upgrades

GEOCOL: from spherical approximation to no approximation. Atmospheric corrections needed as well as correction for pole-tides.

TC: upgrade to be used on gravity gradient data in satellite frame.

COVFIT: upgrade so that Bjerhammar sphere totally included in the Earth is used, and so that covariance functions which does not use spherical approximation may be modeled. Since COVFIT will have to be used after each new gravity model has become available, it would be worthwhile to find a method for automatic determination of the parameters which define an analytic model.

 

The upgrades will be tested using simulated data.

S3.1.3 Prototypes

All the above mentioned programs are in daily use for gravity field modeling of regional data where spherical approximation may be used. The used algorithms are documented in the scientific literature.

S3.1.4 Implementation

 

The prototypes have already been tested in earlier ESA studies. It may not be necessary to upgrade TC. It depends on the use of the program.

 

S3.2 Schedule and manpower

 

The upgrade of GEOCOL has started. Program changes and testing is estimated to 2 mm. It is expected to be finished April 1, 2002.

 

COVFIT and TC upgrades may not be strictly needed. If needed the upgrades will require 2 mm, and should be done in the second half of 2002.

S3.3 Outputs

S3.3.1 Development plan (as in 3.1.1-3.1.4)

GEOCOL: upgrade finished and tested April. 1, 2002.

 

S3.3.2 DRD

 

A document describing the upgrade of GEOCOL ( http://www.gfy.ku.dk/~cct/geocol15.log ) will be updated.

S3.3.3 SWPARD

All the GRAVSOFT modules contain detailed descriptions imbedded in the software. Algorithms are documented by direct reference to the scientific literature. Changes are documented in an update log for GEOCOL.

 

B: Gross-error detection, quick-look validation, data screening.

 

S3.1 Development sequence

 

S3.1.1 Inventory

 

GEOGRIDX: Program for outlier detection by prediction from surrounding data of the same data type, and at the same altitude. It processes the data one by one, using the data within a given pre-defined radius. (Spatially defined covariance functions are not used). This program may be sufficient for quick-look validation and data-screening.

GEOGRIDXX: same as GEOGRIDX, but spatially defined covariance functions are used. Only usable for one data type. Uses fixed covariance function parameters for a region.

GEOCOL: Uses all datatypes, but is not well suited to handle large datasets. Useful for gross-error detection. Uses fixed covariance function parameters for a region.

 

S3.1.2 Software upgrades.

 

GEOGRIDXX must be updated to handle several data-types (gravity gradients) simultaneously-

 

S3.1.3 Prototypes

 

GEOGRIDX, GEOGRIDXX and GEOCOL are all well-tested prototypes.

 

S3.1.4 Implementation

 

The interface is using the GRAVSOFT standard interface.

 

S3.2 Schedule and manpower.

 

The upgrade of GEOGRIDXX require 3 mm. Depending on available staff, the upgrade is scheduled for the last part of 2002.

 

S3.3 Outputs

 

S3.3.1 Development plan (as in 3.1.1-3.1.4)

 

 

S3.3.2 DRD

 

A document describing the updates to GEOGRIDXX will be written.

 

S3.3.3 SWPARD

 

Descriptions of tests are found in the final report of E2M.

 

C: No input.

 

D. Data gaps.

 

 

S3.1 Development sequence

 

S3.1.1 Inventory

 

GEOCOL: the program may be used to fill a data gap by prediction using least-squares collocation.

 

S3.1.2 Software upgrades

 

Upgrade so that spherical approximation is not used needed for large data gaps, see above (A).

 

S3.1.3 Prototypes

 

GEOCOL is a working prototype.

 

S3.1.4 Implementation

 

It is fully implemented, but may need upgrade.

 

S3.2 Schedule and manpower

 

See (A).

 

S3.3 Outputs

 

S3.3.1 Development plan (as in 3.1.1-3.1.4)

See (A)

 

S3.3.2 DRD

See (A)

 

S3.3.3 SWPARD

Update of GEOCOL change log.

 

 

E: No input.