D65    Quality indicator algorithm

Responsible partner
Due date
09 --> 24

This is part of work-package 6500 the purpose of which is:

Objectives:  Increase the robustness and quality of the products by developing an improved quality indicator.

Methodology/Work Description: Most of the GPS software packages provide the standard deviation of the estimated Zenith Total Delay (ZTD) parameter as an estimate of the quality of the solution. The standard deviation is a formal measure of quality computed from the inverse of the normal matrix. As a measure of quality it is seriously flawed because
* It does not take into account the actual quality of the observations,
* It is unaware of important errors such as multipath, and
* It assumes the orbits (and sometimes satellites clocks) are perfect.
The standard deviation is always too optimistic and cannot be used to model the errors during the assimilation into NWP.

A new quality indicator for the ZTD will be developed and tested. The new indicator will be computed from the estimated least squares residuals by using variance component estimation techniques, taking into account the degree of freedom over the domain of the ZTDparameter.

* TUD will develop robust quality indicators dependent on the number of data and degrees of freedom of the geodetic solution
* TUD will distribute the algorithms to be implemented by all processing centre in the first revision of the processing system.

Deliverable D65: The methodology and results can be found in the report: Robust quality indicators. Further details by contact to Hans van der Marel at h.vandermarel@geo.tudelft.nl