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  1. 1. ASTER GDEM<br />IGARRS 2011, Vancouver, Canada<br />Session: TH2.T05.3 ASTER (Thursday, July 28, 10:20 - 12:00)<br />Characteristics of ASTER GDEM Version 2<br />Tetsushi Tachikawa1, Masami Hato1, Manabu Kaku2, Akira Iwasaki3<br />1 Earth Remote Sensing Data Analysis Center (ERSDAC),<br /> 2 Mitsubishi Material Techno Corp., 3 University of Tokyo<br />
  2. 2. ASTER GDEM Project<br />METI/Japan and NASA/USA in conjunction<br /> with ERSDAC and LPDAAC<br />
  3. 3. Status of GDEM Version 2<br />2009<br />2010<br />2011<br />Year<br />7<br />8<br />9<br />10<br />11<br />12<br />11<br />12<br />1<br />2<br />3<br />5<br />6<br />7<br />Month<br />1<br />2<br />3<br />4<br />6<br />8<br />9<br />10<br />Now Validated by<br /><ul><li>USGS
  4. 4. NGA
  5. 5. NASA/JPL
  6. 6. NASA/GSFC
  7. 7. University of Tokyo
  8. 8. ERSDAC</li></ul>Version 1 Release<br />Trial Process<br />Trial Version<br />Version 2 Production<br />Beta Version<br />by SILC<br />Validation<br />New Data<br /> Version 2Release (TBD) <br />ASTER New Observation<br />
  9. 9. ASTER nadir- and backward-looking telescopes (Band3, NIR band) allow acquisition of stereo image pairs<br />Automated processing <br />Terra/ASTER<br />55 sec.<br />Image correlation matching between Band 3Nand Band 3B<br />Band3NNadir<br />Band3BBackward<br />Determination of geolocation at the corresponding point for Band 3N and Band 3B <br />Elevation<br />ASTER Stereo Observation<br />Calculation of elevation <br />
  10. 10. ASTER GDEM Production<br />All ASTER stereo observation(60km*60km*1.2 million scenes)<br />Produce scene DEM<br />ASTER Coverage<br />Calculate elevations by stacking<br />ASTER GDEM<br />Global Coverage<br />Elevation (m)<br />Number of stack (#)<br />
  11. 11. New algorithm<br />Finer horizontal resolutionThe elevation is calculated by image matching of ASTER stereo pair. The kernel size for image correlation matching is changed to 5 by 5 pixel from 9 by 9 pixel.<br />Offset adjustmentEvery calculated scene DEM has elevation offset of -5m.This offset (-5m) is adjusted.<br />Water body detectionGDEM version 1 could detect lakes larger than about 12km2.This improves to 1km2 in version 2.<br />New observed data<br />GDEM version 2 incorporates new ASTER data observed after September 2008. The voids and artifacts caused by lack of ASTER data will be improved.<br />Updates in GDEM Version2<br />
  12. 12. Estimate Horizontal and Elevation Error<br />553701<br />553702<br />553801<br />553802<br />543703<br />543704<br />543803<br />543804<br />543701<br />543702<br />543801<br />543802<br />533703<br />533704<br />533803<br />533804<br />533701<br />533702<br />533801<br />533802<br />523703<br />523704<br />523803<br />523804<br />GSI 10m-grid DEM covers all the land of Japan<br />GSI (The Geospatial Information Authority of Japan)<br />
  13. 13. Method to Estimate Horizontal Error<br />13 grid square = 169 grids<br />ASTER GDEM<br />169 grids of elevation error (m)<br />0.4 arc-second<br />SD of elevation errors (m)<br />Move 13 grid square and repeat<br />2 dimensional mapping<br />Calculate the lowest location<br />GSI 10m-grid<br />DEM<br />SD<br />NS<br />EW<br />
  14. 14. Horizontal Error<br />N-S Geolocation Error (arc-second)<br />1.0arc-second<br />0.5arc-second<br />E-W Geolocation Error (arc-second)<br />
  15. 15. Standard Deviation of Elevation Error<br />SD of Elevation Error (m)<br />Average of Version 1<br />Average of Version 2<br />
  16. 16. Offset Estimation<br />Offset is estimated in ‘Rice Farm’ and ‘Farm’ as open area.<br />“Subdivision Land Use Data of Digital National Land Information”<br />produced by the GSI Japan. <br />
  17. 17. Offset Estimation<br />Offset is estimated as -0.7 m.<br />Frequency<br />Elevation Error (m)<br />
  18. 18. Horizontal Resolution<br />Version 1<br />Version 1<br />Version 2<br />
  19. 19. Version 2<br />Version 1<br />GDEM<br />0<br />4000<br />m<br />Resolution:1arc-sec<br />Resolution:2arc-sec<br />Resolution:3arc-sec<br />Resolution:4arc-sec<br />Reference DEM(Degraded 10m DEM)<br />0<br />4000<br />m<br />Elevation<br />Error<br />-50<br />+50<br />0<br />m<br />m<br />Standard Dev.<br />14.489<br />13.022<br />13.122<br />13.993<br />Method to Estimate Resolution<br />
  20. 20. Estimated Resolution<br />Standard Deviation of Elevation Error (m)<br />3.8 (114m)<br />2.4 (72m)<br />Horizontal Resolution (arc second) of Reference DEM<br />
  21. 21. Error Estimation of Version 2<br />*1 arc-second corresponds to 30m<br />
  22. 22. Improvement of Voids in Northern Area<br />Version 2<br />Version 1<br />
  23. 23. Version 2<br />Improvement of Voids in Northern Area<br />Version 1<br />
  24. 24. Improvement of Artifacts<br />Version 1<br />S31E023 1200x1200 arc-second<br />01234567890123456789012<br />filled<br />1000<br />2000<br />Stacking Number<br />Elevation (m)<br />
  25. 25. Improvement of Artifacts<br />Version 2<br />S31E023 1200x1200 arc-second<br />01234567890123456789012<br />filled<br />1000<br />2000<br />Stacking Number<br />Elevation (m)<br />
  26. 26. Improvement of Artifacts<br />Ver.2<br />Ver.1<br />Ver.1<br />Ver.2<br />
  27. 27. Improvement of Water Body<br />Version 2<br />Version 1<br />Lake Nicaragua<br />Lake Nicaragua<br />N11W086 1200x1200 arc-second<br />0<br />800<br />Elevation (m)<br />
  28. 28. Improvement of Water Body<br />Ver.2<br />Lake Nicaragua<br />Lake Nicaragua<br />Ver.1<br />Ver.1<br />Ver.2<br />
  29. 29. Improvements of Version 2<br />#Stack increase to three or more in most of the lack area.<br />Voids in northern area<br />Decrease<br />Artifacts (step, Pit-in-bump, Mole-run, etc.)<br />Almost disappear<br />New water body detection algorithm<br />Lakes are perfectly flat.<br />Step<br />Artifacts<br />Pit-in-bump<br />Mole-run<br />
  30. 30. Summary<br />Main characteristics of ASTER GDEM version 2<br />Resolution improves to 70m from 110m (version 1).<br /><ul><li>Offset reduces to -0.7m from -6m (version 1).</li></ul>Voids in northern area decrease.<br />Artifacts mostly disappear.<br />Lakes are perfectly flat.<br />