Honeywell Technology Solutions Inc AWG Meeting, Washington DC, Oct 3-4, 2002 Comparison of ILRS Station Positions (“AA” & “A” Series, i.e. 1999) Van Husson

Honeywell Technology Solutions Inc AWG Meeting, Washington DC, Oct 3-4, NP Data Volume

Honeywell Technology Solutions Inc AWG Meeting, Washington DC, Oct 3-4, Performance Problems

Honeywell Technology Solutions Inc AWG Meeting, Washington DC, Oct 3-4, Height Standard Deviations

Honeywell Technology Solutions Inc AWG Meeting, Washington DC, Oct 3-4, Avg. Height Variations (best 12 sites)

Honeywell Technology Solutions Inc AWG Meeting, Washington DC, Oct 3-4, 2002 “A” Series Data Treatment by site/28 days There are significant differences in data treatment. 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

Honeywell Technology Solutions Inc AWG Meeting, Washington DC, Oct 3-4, 2002 “AA” Series Data Treatment by site/28 days The data treatment differences are vanishing. Will this map into less deviations in site heights? 1. For the better sites, assumed no biases, for other sites RB estimated once/28 days.

Honeywell Technology Solutions Inc AWG Meeting, Washington DC, Oct 3-4, 2002 OMC(mm) Monument PeakMcDonaldGreenbelt HerstmonceuxGrasseGraz YarragadeeMt. Stromlo OMC(mm) ASI Analysis (Sol “A” V1) (state vector error)

Honeywell Technology Solutions Inc AWG Meeting, Washington DC, Oct 3-4, 2002 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? Effect of Modeling Errors Modeling ErrorRange Bias Radial Height Baselines Scale

Honeywell Technology Solutions Inc AWG Meeting, Washington DC, Oct 3-4, 2002 ASI Analysis (Solution Comparison) Height(mm) Monument PeakMcDonaldGreenbelt HerstmonceuxGrasseGraz YarragadeeMt. Stromlo Height(mm) SolAA.V1 (no rb estimation) SolA.V3 (rb estimation) SolA.V1 (state vector error)

Honeywell Technology Solutions Inc AWG Meeting, Washington DC, Oct 3-4, 2002 CRL Analysis (Solution Comparison) Height(mm) Monument PeakMcDonaldGreenbelt HerstmonceuxGrasseGraz YarragadeeMt. Stromlo Height(mm) SolAA.V1 (no rb estimation) SolA.V1 (rb estimation)

Honeywell Technology Solutions Inc AWG Meeting, Washington DC, Oct 3-4, 2002 NERC Analysis (Solution Comparison) Height(mm) Monument PeakMcDonaldGreenbelt HerstmonceuxGrasseGraz YarragadeeMt. Stromlo Height(mm) SolAA.V1 (no rb estimation) SolA.V1 (rb estimation) Fixed error in sat. once/rev acceleration between SolA.V1 and SolAA.V1.

Honeywell Technology Solutions Inc AWG Meeting, Washington DC, Oct 3-4, 2002 JCET Solution Comparisons JCET AJCET AA

Honeywell Technology Solutions Inc AWG Meeting, Washington DC, Oct 3-4, Height Agreement by Region

Honeywell Technology Solutions Inc AWG Meeting, Washington DC, Oct 3-4, Range Bias Comparison Range bias estimates averaged over the year are in excellent agreement Longitude

Honeywell Technology Solutions Inc AWG Meeting, Washington DC, Oct 3-4, 2002 Height Comparisons ASI AACRL AAJCET AA

Honeywell Technology Solutions Inc AWG Meeting, Washington DC, Oct 3-4, Height Comparisons IAAK A CSR A DGFI A

Honeywell Technology Solutions Inc AWG Meeting, Washington DC, Oct 3-4, Height Comparisons NERC AA

Honeywell Technology Solutions Inc AWG Meeting, Washington DC, Oct 3-4, 2002 Solution Comparisons Height(mm) Monument PeakMcDonaldGreenbelt HerstmonceuxGrasseGraz YarragadeeMt. Stromlo Height(mm) JCET CSR ASI DGFI CRL IAAK NERC

Honeywell Technology Solutions Inc AWG Meeting, Washington DC, Oct 3-4, 2002 EUROLAS Comparisons Height(mm) PotsdamGrasse LLRZimmerwald HerstmonceuxGrasseGraz BorowiecWettzell Height(mm) JCET CSR ASI DGFI CRL IAAK NERC

Honeywell Technology Solutions Inc AWG Meeting, Washington DC, Oct 3-4, Zimmerwald Height Case Study Large variation, distribution appears bimodal on either side of ITRF2000 height. Why? CRL DGFI IAAK NERC CSR ASI ITRF2000 CRL, DGFI, & IAAK assumed no range bias. But NERC, CSR, & ASI estimated a range bias.

Honeywell Technology Solutions Inc AWG Meeting, Washington DC, Oct 3-4, 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. CRL DGFI IAAK NERC CSR ASI ITRF2000

Honeywell Technology Solutions Inc AWG Meeting, Washington DC, Oct 3-4, 2002 McDonald Case Study McDonald, Null RB McDonald AA and A

Honeywell Technology Solutions Inc AWG Meeting, Washington DC, Oct 3-4, 2002 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

Honeywell Technology Solutions Inc AWG Meeting, Washington DC, Oct 3-4, 2002 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

Honeywell Technology Solutions Inc AWG Meeting, Washington DC, Oct 3-4, 2002 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