D69    Regional combination methodology and report.

Responsible partner
Due date
09 --> 24

This is part of work-package 9500 the purpose of which is:

Objectives:  In a distributed network processing approach, a method is required for ensuring the results from the processing centres are compatible.

Methodology/Work Description: The International GPS Service (IGS) has developed a method for combining ZTD solutions from different processing centres by removing a bias between processing centres and averaging the results. The same method is applied for the 12 analysis centres of the EUREF Permanent GPS Network (EPN). Typical for IGS and EUREF is, that almost all stations are processed by at least three processing centres.

In our distributed network, only a subset of stations will be common among processing centres, but these can be used to verify that there are no offsets. Also, IGS and EUREF operate in post-processing mode.

The batch type of processing used by IGS and EUREF will be converted into a Kalman filter approach that can be used in near real-time applications. The differential biases between the analysis centres will be modelled for the stations in common. Special techniques for the detection, identification and adaptation of outliers and biases, developed at TUD, will be used. Algorithms will be developed and tested.

* Two possible refinements will be investigated
 1. Extension or combination of the NRT combination with bias reduction algorithms (using output from NWP analysis) to model absolute biases, 
 2. The use of error correlation models to provide analysis centre dependent corrections for stations that are not in common.
Both of these additional investigations are related to other workpackages in this proposal.

* TUD will develop automated methodology for a regional combination of solutions following the EUREF model, in order to provide the best integrated product from the regional products. They will aid in the implementation of this methodology at the processing centres.

Deliverable D69: The  results are available in the report: Sequential combination of regional troposphere solutions.  For further information contact Hans van der Marel at the Technical University of Delft.