1. Connecticut Height Modernization 2010 Thomas H Meyer (UConn) Robert Baron (CT DOT) Darek Massalski (CT DOT) Kazi Arifuzzaman (UConn) 1

2. Overview Goal: to assess the accuracy of GEOID03 and GEOID09 in Connecticut Goal: to assess the accuracy of GEOID03 and GEOID09 in Connecticut Means: how well do GPS-determined orthometric heights compare with NAVD 88 published heights Means: how well do GPS-determined orthometric heights compare with NAVD 88 published heights 2

3. Markers 70 markers 70 markers 22 class A 22 class A 10 class B 10 class B 11 class C 11 class C 2 class D 2 class D 25 transfers 25 transfers 3

4. 4

5. Occupations 2007-2008 2007-2008 Summer, Fall Summer, Fall Only First-Order bench marks Only First-Order bench marks At least three occupations per mark At least three occupations per mark 4 hour duration 4 hour duration Re-level range pole each hour Re-level range pole each hour 5

6. GPS Equipment Receivers Receivers UConn UConn TOPCON HipPer Lite+ (internal) TOPCON HipPer Lite+ (internal) Javad Legacy (LegAnt) Javad Legacy (LegAnt) Odyssey (internal) Odyssey (internal) CTDOT CTDOT Trimble 5700 (Zephyr) Trimble 5700 (Zephyr) 2-m, fixed-height tripods 2-m, fixed-height tripods 6

7. GPS Processing Pinnacle and OPUS Pinnacle and OPUS RINEX v.2 RINEX v.2 IGS precise ephemerides IGS precise ephemerides NGS guidelines NGS guidelines CORS for control (no benchmarks) CORS for control (no benchmarks) 7

8. Checks Pinnacle vectors against CORS inversed vectors Pinnacle vectors against CORS inversed vectors None statistically different (95%) None statistically different (95%) Pinnacle and OPUS Pinnacle and OPUS Compare ellipsoid heights Compare ellipsoid heights Different differencing kernels Different differencing kernels 8

9. Pinnacle h – OPUS h Letters/colors indicate stability classes Box-whisker plot Dots indicate outliers. 9

10. Pinnacle – OPUS no outliers Error-bar plot Frequency histogram 10

11. Conclusion Pinnacle seems to be producing ellipsoid heights that are consistent with PAGES Pinnacle seems to be producing ellipsoid heights that are consistent with PAGES 11

12. Networks NGS specifications NGS specifications No “bad” vectors No “bad” vectors All vectors, including substandard All vectors, including substandard No phase-center variation correction No phase-center variation correction 12

13. Marker Locations Letter indicates stability class. Circles indicate stdev (1-s) of H G03 and H G09. Black: too low; red: too high. 13

14. General Results H G03 – H 88 and H G09 – H 88 Box-whisker plots 14

15. Frequency Histogram 15

16. By Stability Class Class A and transfers the same. Others indicate settling. 16

17. Residual Trend Analysis Normalize eastings and northings Normalize eastings and northings (-1, 1), unit variance (-1, 1), unit variance Fit a plane through differences Fit a plane through differences Constant terms (These are consistent with Tranes et al. [2007]) Constant terms (These are consistent with Tranes et al. [2007]) GEOID03: -0.012 m (significant (99%) ) GEOID03: -0.012 m (significant (99%) ) GEOID09: -0.017 m (significant (99%) ) GEOID09: -0.017 m (significant (99%) ) Slope terms Slope terms GEOID03: significant (99%) GEOID03: significant (99%) GEOID09: not significant (99%) GEOID09: not significant (99%) 17

18. Conclusions 1. GEOID03 and GEOID09 are accurate at their stated levels in CT 2. GEOID09 out-performed GEOID03 3. H G03 and H G09 too low by about 1 cm 1. Subsidence 2. Re-observe the bench marks 3. No “correction surface” warranted 18

19. Thomas.meyer@uconn.edu http://www.nre.uconn.edu/Faculty_and_Staff/Meyer.php 19