ARCGICE WP 5.1 Leader: UCL Synthesis report on benefit of combining data C.C.Tscherning, University of Copenhagen,

Observations: Parameter is equal to N 0 mean sea surface height A i = 1 if bias only for all values of i which are associated with geoid heights. Parameter and error-estimation C.C.Tscherning, University of Copenhagen,

Then an estimate of T and of the parameters X are obtained as where W is the a-priori weight matrix for the parameters (Generally the zero matrix). Parameter estimate C.C.Tscherning, University of Copenhagen,

The associated error estimates are with the mean square error of the parameter vector and the mean square error of an estimated quantity. Error-estimates C.C.Tscherning, University of Copenhagen,

1.From knowledge of survey type or data- collection method. 2.From comparison with independent sources such as MSS from WP From comparison of two sources in same area. Spatial errors C.C.Tscherning, University of Copenhagen,

Least-squares collocation with parameters may be used to combine data dependent on gravity field and a few other physical parameters. Data-combination C.C.Tscherning, University of Copenhagen,