| Date: | 2003-08-06 19:24:00 | |
| Sender: | Van S. Husson <Husson, Van <Van.Husson@honeywell-tsi.com>> | |
| Subject: | [SLR-Mail] No. 1111: 7832 Riyadh ITRF coordinates | |
| Author: | Van S. Husson | |
| Content: | ******************************************************************************** SLR Electronic Mail 2003-08-06 19:24:00 UTC Message No. 1111 ******************************************************************************** Author: Van S. Husson Subject: 7832 Riyadh ITRF coordinates Dear Colleagues, Yesterday, I sent a message to the ILRS analysis community alerting them that the ITRF2000 station position for Riyadh (7832) had a large error. Many people within the ILRS analysis community were aware of this problem. I also invited analysis centers to contribute a revised set of Riyadh coordinates. So far, two groups (ASI and CSR) have furnished their coordinate sets (Thanks to Cinzia Luceri and John Ries for the fast response). Below are their revised coordinate sets: ASI SOLUTION ------------ The ASI coordinate set is based on her geodetic solution from Lageos-1 and Lageos-2 data, covering the period January 1984 to January 2002. For Riyadh, she used all their data including 1996 and 1997. The solution is constrained to ITRF2000. The values, at epoch 1997.0, are: X(m): 3992101.028 +/- 0.001 Y(m): 4192172.505 +/- 0.002 Z(m): 2670410.719 +/- 0.001 XDOT(m/yr): -0.0297 +/- 0.0004 YDOT(m/yr): 0.0151 +/- 0.0004 ZDOT(m/yr): 0.0244 +/- 0.0004 Transformed into Up, East, North Up: 1.6 mm/year North: +26.3 mm/year East: +31.9 mm/year CSR´s JASON SOLUTION -------------------- Below is CSR´s Riyadh position estimate and velocity using Riyadh Jason (not LAGEOS) data from Jan 2001 to Jul 2002 at epoch Jan 1997. X(m): 3992100.9847 Y(m): 4192172.5231 Z(m): 2670410.7150 XDOT(m/yr): -0.02813 YDOT(m/yr): 0.01282 ZDOT(m/yr): 0.02578 Transformed into Up, East, North Up: 1.7 mm/year North: +27.6 mm/year East: +29.2 mm/year CSR and ASI SOLUTION COMPARISON ------------------------------- The UNE rates from both solutions are very close in all 3 components. At epoch Jan 2002 the offsets in the three components are: Up(mm): 16 North(mm): 10 East(mm): 30 I´m confident that a in-depth range/time bias estimation analysis using Riyadh LAGEOS-1, LAGEOS-2 and Jason data would resolve the above differences. To conclude, the ILRS strongly encourages the space geodetic analysis community to NOT use the ITRF2000 Riyadh station position and either use your own set or one of the above sets. From: ”Husson, Van” ******************************************************************************** |