1 / 15

GEOID03 in Louisiana and Alaska

GEOID03 in Louisiana and Alaska. Dr. Yan M Wang and Dr. Daniel R Roman Geodesist, NGS/NOAA ACSM Annual Conference and Technology Exhibition Orlando, FL April 21-26, 2006. Outline. GEOID03 update in Louisiana GEOID03 in Alaska. Geoid03 update in Louisiana.

illias
Download Presentation

GEOID03 in Louisiana and Alaska

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. GEOID03 in Louisiana and Alaska Dr. Yan M Wang and Dr. Daniel R Roman Geodesist, NGS/NOAA ACSM Annual Conference and Technology Exhibition Orlando, FL April 21-26, 2006

  2. Outline • GEOID03 update in Louisiana • GEOID03 in Alaska

  3. Geoid03 update in Louisiana • Subsidence corrections to the leveling network (85 pts) provided by LSRC • Subsidence corrections are computed from a model, and further improvement is expected • The leveling network will be readjusted in the National Spatial Reference System in February, 2007.

  4. Few Remarks • Updated Vertical Time-dependent Positioning bench marks must be used for all applications • New survey along one long level line of 40 km, running from the coast inland as close to North/South is under discussion

  5. The Geoid in Alaska • NGS has computed a gravimetric geoid for Alaska as a separate computational area since GEOID96 • Gravimetric only; No hybrid possible • Lack of wide-spread GPS on leveled benchmarks • Refers to ITRF origin, not NAD 83

  6. Simplified Concept of NAD 83 vs. ITRF Earth’s Surface hNAD83 hITRF hNAD83 – hITRF varies smoothly by latitude and longitude ITRFxx origin ~2.24 m NAD 83 origin

  7. Gravity Holdings Zoom near Nome - Note lack of good near-shore data - Some sparseness in terrestrial network - Airborne gravity could solve both of these

  8. GEOID99 vs GEOID03 in Alaska • An error in how OPUS estimates orthometric heights was found during FAA airport surveys • OPUS/GPS yields NAD 83 ellispoid height • GEOID99 is an ITRF/GRS80 geoid height • Incompatible! • GEOID03 was created in Alaska to fix this problem

  9. Alaskan GEOID99 vs GEOID03 Earth’s Surface hNAD83 GEOID03 (refers to NAD 83 centered ellipsoid) GEOID99 (refers to ITRF96 centered ellipsoid) hITRF00 N03 N99 Note: Physical location of geoid In space has not changed from 99 to 03! ITRF96 origin Geoid ~2.24 m Erroneously, OPUS was doing: H≈h83-N99 Now, correctly, OPUS does: H≈h83-N03 NAD 83 origin

  10. The Geoid in Alaska (2) • Ongoing research • GPS on leveled benchmarks vs GEOID03 • Accuracy assessments • Better theory • Better data • Airborne gravity • Most logical way to collect accurate data in areas previously unvisited

  11. Final snag: Heights change over time! • All heights needs monitoring: • Crustal motion (affects H, h) • Gravity changes (affects H, N) • h=H+N • Monitoring can be done efficiently: • GPS for crustal monitoring • Spot gravity re-visits for gravity monitoring • Re-leveling is not efficient • Lest we forget, Alaska has some very active geology…

  12. Questions/Comments? • Dr. Yan M Wang and Dr. Daniel R Roman • Geodesist, National Geodetic Survey • Yan.Wang@noaa.gov • 301-713-3202 x 127 • Dan.Roman@noss.gov • 301-713-3202 x 161

More Related