Ellipsoidal Height References, GPS Data archiving and Standards for AUSPos

1. Ellipsoidal Height References, GPS Data archiving and Standards for AUSPos Gary Johnston

2. Datum choice for Height Modernisation Non consistency of reference frames Non homogeneity of GPS epochs Collection of appropriate GPS data for archival and refined reprocessing when appropriate Morgan Sinex solution Issues

3. Datum choice for Height Modernisation • ITRF2000 is the “current” latest and greatest • Epoch 2000.0 is near the mean date of JP survey observations • Real time positioning services use ITRF or WGS84 which is ITRF aligned

4. Non consistency of reference frames • GDA94, ITRF92, ITRF97, ITRF2000 • Difference exist between ITRF realisations • GDA94 differs from the pure ITRF92 • Impact can be ~0.1m in Height • Transformation removes most but not all the error

8. ITRF92@1994.0 to ITRF2000@2000 IERS Residuals

9. Non-Homogeneity of GPS epoch • AHD TGBM campaign 99135 – 00125 • JP survey 1999 – 2004 • GDA GPS (Tas) 1993 • Validation data 1990 > • SWSZ 2002, 2004 • SASZ 2003,2004

10. Karratha

11. Townsville

12. DSTO

13. Morgan Solution • Fiducial free SINEX files for ANN, ABSLMA95, ABSLMA98, TGBM99, WA STATEFIX and ARGN • Map to epoch of choice • Use whichever ITRF we choose • Gives link between ARGN and ANN etc including VCV • Uses mapping function to map to common epoch

14. Morgan (2004) Points

15. Collection of appropriate GPS data for archival and refined reprocessing when appropriate • Large amount of data collected and processed thru AUSPos etc • Reference frames and epochs change • GPS models change • Processing gets faster and easier • Data can be used for multiple purposes