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Comparison of ILRS Station Positions (“AA” & “A” Series, i.e. 1999)

Comparison of ILRS Station Positions (“AA” & “A” Series, i.e. 1999). Van Husson. 1999 NP Data Volume. 1999 Performance Problems. 1999 Height Standard Deviations. 1999 Avg. Height Variations (best 12 sites). “A” Series Data Treatment by site/28 days.

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Comparison of ILRS Station Positions (“AA” & “A” Series, i.e. 1999)

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  1. Comparison of ILRS Station Positions (“AA” & “A” Series, i.e. 1999) Van Husson

  2. 1999 NP Data Volume

  3. 1999 Performance Problems

  4. 1999 Height Standard Deviations

  5. 1999 Avg. Height Variations(best 12 sites)

  6. “A” Series Data Treatmentby site/28 days 1. DGFI estimated pass-by-pass biases, when the suspected range or time bias exceeded 30mm or 30 microseconds, respectively. 2. IAAK assumed no biases, except a constant RB for Maidanak and Komsomolsk 3. For the core sites, assumed no biases, for other sites RB estimated every 7 days per satellite There are significant differences in data treatment.

  7. “AA” Series Data Treatmentby site/28 days 1. For the better sites, assumed no biases, for other sites RB estimated once/28 days. The data treatment differences are vanishing. Will this map into less deviations in site heights?

  8. ASI Analysis (Sol “A” V1)(state vector error) Monument Peak McDonald Greenbelt OMC(mm) Herstmonceux Grasse Graz OMC(mm) Yarragadee Mt. Stromlo OMC(mm)

  9. Effect of Modeling Errors Any modeling errors (e.g. GM, satellite CoM, troposphere, biases, data weighting, data treatment) will be absorbed into the station coordinates, mostly height. What can be done to mitigate these errors? Radial Height Baselines Scale Modeling Error Range Bias

  10. SolAA.V1 (no rb estimation) SolA.V3 (rb estimation) SolA.V1 (state vector error) ASI Analysis (Solution Comparison) Monument Peak McDonald Greenbelt Height(mm) Herstmonceux Grasse Graz Height(mm) Yarragadee Mt. Stromlo Height(mm)

  11. SolAA.V1 (no rb estimation) SolA.V1 (rb estimation) CRL Analysis (Solution Comparison) Monument Peak McDonald Greenbelt Height(mm) Herstmonceux Grasse Graz Height(mm) Yarragadee Mt. Stromlo Height(mm)

  12. SolAA.V1 (no rb estimation) SolA.V1 (rb estimation) NERC Analysis (Solution Comparison) Monument Peak McDonald Greenbelt Height(mm) Herstmonceux Grasse Graz Height(mm) Yarragadee Mt. Stromlo Height(mm) Fixed error in sat. once/rev acceleration between SolA.V1 and SolAA.V1.

  13. JCET A JCET AA JCET Solution Comparisons

  14. 1999 Height Agreement by Region

  15. 1999 Range Bias Comparison Longitude Range bias estimates averaged over the year are in excellent agreement

  16. JCET AA ASI AA CRL AA Height Comparisons

  17. CSR A 1999 Height Comparisons IAAK A DGFI A

  18. NERC AA 1999 Height Comparisons

  19. JCET CSR ASI DGFI CRL IAAK NERC Solution Comparisons Monument Peak McDonald Greenbelt Height(mm) Herstmonceux Grasse Graz Height(mm) Yarragadee Mt. Stromlo Height(mm)

  20. JCET CSR ASI DGFI CRL IAAK NERC EUROLAS Comparisons Potsdam Grasse LLR Zimmerwald Height(mm) Herstmonceux Grasse Graz Height(mm) Borowiec Wettzell Height(mm)

  21. CRL DGFI IAAK NERC CSR ASI ITRF2000 1999 Zimmerwald Height Case Study CRL, DGFI, & IAAK assumed no range bias. But NERC, CSR, & ASI estimated a range bias. Large variation, distribution appears bimodal on either side of ITRF2000 height. Why?

  22. CRL DGFI IAAK NERC CSR ASI ITRF2000 1999 Zimmerwald Height Case Study Much less height variation, if every group applied a –18mm apriori range bias (later confirmed by engineering analysis). Average height about 10mm short of ITRF2000 height. This explains the 7-8mm offset in the local tie.

  23. McDonald Case Study McDonald AA and A McDonald, Null RB

  24. Lessons learned • Modeling errors have significant influence on apparent station positions • Range bias is an important quality control tool for the sites and the station position solutions • 4-7mm RMSs appear to be a reasonable height RMS for a full year of 28 day solution

  25. Future Challenges • Complete Phase I of the benchmark project and take the lessons learned and apply them to the POS/EOP project • Implement the data corrections file • Implement new LAGEOS CoM • Estimate new GM

  26. Remarks • We are beginning to adopt some BEST modeling practices and the solutions are converging as a result. Some more work is needed. • We are getting close to the optimum strategy for handling of biases to get the BEST heights, but we are not there yet. • Range bias analysis combined with site height analysis can resolve local tie issues

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