1 / 31

Daniel R. Roman and Vicki A. Childers

45 th Annual Alaska Surveying & Mapping Conference February 21-25, 2011 Hilton Anchorage Hotel Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska Part III: Geoid Modeling. Daniel R. Roman and Vicki A. Childers. Outline. Introduction Crossovers

lance-oconnor
Download Presentation

Daniel R. Roman and Vicki A. Childers

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. 45th Annual Alaska Surveying & Mapping ConferenceFebruary 21-25, 2011 Hilton Anchorage Hotel Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska Part III: Geoid Modeling Daniel R. Roman and Vicki A. Childers

  2. Outline • Introduction • Crossovers • Gridded Residual Gravity • Equivalent Geopotential • Residual Terrain Modeling • Future Geoid Models • Outlook Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska Thursday, 0800-1200

  3. Introduction • Airborne gravity = Aerogravity • Relative gravity observations (i.e., need a base) • Collected on a fast-moving platform (400-500 kmh) • Kinematic GPS fixes positions • Also helps to determine gravity (a/c accelerations) • Very complicated process to “observe” aerogravity • Product is a function of observations and processing • Lastly, it is observed at very high altitudes (20 kft) Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska Thursday, 0800-1200

  4. Purpose of GRAV-D • Aerogravity are for a geoid – not a gravity grid • A pattern of observation poor for gravity might be sufficient for geoid determination • The longest wavelengths affect the geoid • Gravity data highlight shorter wavelengths • Random gravity observation errors are “short” • Transformation into geoid effectively removes • Systematic errors are the cause of geoid errors Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska Thursday, 0800-1200

  5. Creating a Gravimetric Geoid • Satellites provide global consistency & accuracy • GRACE has been up a long time – likely follow-on • GOCE supplements coverage of GRACE • Combined satellite model would cover 200 km > • Significant errors exist below 200 km • GRAV-D aerogravity will help to resolve these • Terrain modeling captures the smallest features • Melding all these together remains the challenge Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska Thursday, 0800-1200

  6. Crossover Plots for AK08 Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska Thursday, 0800-1200

  7. AK08 Residual Gravity Profiles Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska Thursday, 0800-1200

  8. AK08 Residual Geopotential (N=1440) Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska Thursday, 0800-1200

  9. AK08 Residual Geopotential (Min=175, Max=1440) Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska Thursday, 0800-1200

  10. Crossover Plots for AK09 Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska Thursday, 0800-1200

  11. AK09 Gridded Residual Gravity

  12. AK09 Residual Geopotential (N=1440) Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska Thursday, 0800-1200

  13. AK09 Residual Geopotential (Min=175, Max=1440) Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska Thursday, 0800-1200

  14. Statewide Geoid Modeling • Each month-long survey covers 400x500 km • All surveys collected in a consistent manner • All constrained to a GRACE/GOCE model • GRACE/GOCE will account for long wavelengths • Aerogravity will bridge the gap to surface data • Shortest wavelengths will come from DEM’s • Must properly account for all these signals • “Short” wavelength gravity can have big effects Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska Thursday, 0800-1200

  15. Residual Terrain Modeling • Terrain creates the smallest gravity signal • Density contrast between rock and air • EGM2008 accounted for signal to 5’ (10 km) • Remaining signal between 5’ and 3” (90 m) • This neglected signal has a systematic effect • Examples are given for CONUS and Alaska Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska Thursday, 0800-1200

  16. Point Gravity Minus EGM2008 Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska Thursday, 0800-1200

  17. RTM Gravity Signal from 3” to 5’ Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska Thursday, 0800-1200

  18. Point Gravity Less EGM2008 and RTM Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska Thursday, 0800-1200

  19. Filtered Residual Gravity Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska Thursday, 0800-1200

  20. Equivalent Residual Geoid Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska Thursday, 0800-1200

  21. Alaska RTM • For CONUS, SRTM was available for uniformity • In Alaska, several models were melded into one • SRTM below 60 N Latitude • NED was used for Alaska • CDED was used in Canada • GTOPO30 was used in Russia • Dr. Xiaopeng Li used GPSBM’s to unify them all • Final grid is improved, but probably not consistent • ASTER was looked at but didn’t perform as well Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska Thursday, 0800-1200

  22. Combined Terrain Models Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska Thursday, 0800-1200

  23. Alaska DEM (USGG2009) Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska Thursday, 0800-1200

  24. Point Gravity Minus EGM2008 Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska Thursday, 0800-1200

  25. RTM Gravity Signal from 3” to 5’ Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska Thursday, 0800-1200

  26. Point Gravity Less EGM2008 and RTM Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska Thursday, 0800-1200

  27. RTM Summary • RTM signal 3”-5’ significantly helped • Residual gravity much reduced • DEM for CONUS is from SRTM 3” – uniformity • DEM for Alaska built from many sources • In CONUS, long wavelength residuals • Small signal but yields big geoid residual • No equivalent signal for Alaska – too many gaps Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska Thursday, 0800-1200

  28. Future Geoid Models • By the end 2012, plan is to be about 80% done • Comparison to Canadian data in overlap regions • Potentially, in next national gravimetric geoid • (e.g. USGG20xx) • GRACE/GOCE - long wavelengths (200 km >) • Aerogravity – mid-wavelengths (20 - 400 km) • RTM – short wavelengths (0.1 – 20 km) • Terrestrial gravity – all wavelengths – just too few Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska Thursday, 0800-1200

  29. Outlook • Aerogravity is improving local gravity field • Significant improvements being implemented • Aim is for 2 mgal crossovers or better • Random errors have minimal impact • Systematic errors create geoid errors • Aerogravity will bridge satellite and terrestrial • DEM’s provide shortest wavelengths • Satellite, airborne, terrestrial, & terrain all merged • Removing errors in each yields an accurate geoid Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska Thursday, 0800-1200

  30. Questions? • Aerogravity Team • Vicki A. Childers, Ph.D. • Theresa Diehl, Ph.D. • Sandra A. Preaux (DST) • Processing Support • William Waickman • Xu Yang (SGT) Websites • http://www.ngs.noaa.gov/GEOID/ • http://www.ngs.noaa.gov/GRAV-D/ GEOID Team Daniel R. Roman, Ph.D. Yan Ming Wang, Ph.D. Xiaopeng Li, Ph.D. (ERT) Simon Holmes, Ph.D. (SGT) Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska Thursday, 0800-1200 30

  31. Why we didn’t use Aster Impact of Airborne Gravity Surveys on Geoid Modeling in Alaska Thursday, 0800-1200

More Related