Enhance DynAdjust to apply geoid model uncertainties

[Splinter31]

Brief description
An enhancement to DynAdjust is required to interpolate uncertainty from geoid model grids and apply to ellipsoidal height uncertainties to derive orthometric height uncertainties

Background
The AUSGeoid2020 model and Australian Gravimetric Quasigeoid (AGQG) model include uncertainty fields. When the AUSGeoid2020 model or AGQG model are applied in DynAdjust to compute an orthometric height, the geoid model uncertainty should also be combined with the ellipsoid height uncertainty to provide an orthometric height uncertainty.

This functionality will be applied to GDA2020 adjustment ellipsoidal height uncertainty to produce an estimate of AHD or AVWS height uncertainty. The same functionality can be applied to orthometric height uncertainty to derive ellipsoidal height uncertainty.

The geoid model grid files are available here:
https://www.ga.gov.au/scientific-topics/positioning-navigation/australian-geospatial-reference-system/agrstoolsandmodels

Basic requirements
When the AUSGeoid2020 model or AGQG model are applied in DynAdjust to compute an orthometric height, the geoid model uncertainty should also be combined with the ellipsoid height uncertainty to provide an orthometric height uncertainty.

The geoid model uncertainty can be interpolated from the geoid model grid file. This can be done using the same bicubic interpolation used to derive the geoid-ellipsoid separation values from the grid file. The geoid model uncertainty can then be combined with the ellipsoidal height uncertainty through propagation of variances.

A similar process can be applied to derive ellipsoidal height uncertainties when only an orthometric height uncertainty is available.

Priority
feature new