1. Generation of a Digital Elevation Model using high resolution satellite images By Mr. Yottanut Paluang FoS: RS&GIS

2. Presentation Outline 1.Introduction 2.Methodology 3.Result of this study 4.Conclusion

3. Introduction Digital elevation models (DEMs) are increasingly used for visual and mathematical analysis of topography, landscapes and landforms as well as modeling of surface processes. This study attempts to find out the quality assessment of DEM products using different satellite images including ASTER and ALOS PRISM stereo image, comparing existing DEM. Three techniques are used to validate the result of DEM products ALOS PRISM ASTER DEM Generation

4. Objectives 1. To fuse DEM from ASTER and ALOS PRISM satellite imagery. 2. To evaluate the derived DEM for the suitability in term of terrain surface application. 3. To verify the result of DEM for several terrain surface in term of application suitability.

5. Study Area Map of the Study area

6. 6 1.Introduction 2.Methodology 3.Result of this study 4.Conclusion Presentation Outline

7. 7 Available data Material NameData Description Producing or Acquisition Remark ASTER Image Pair Level 1A VNIR Band 3 nadir and backward views, spatial resolution 15 m 20050107 (acquisition date) The data source of this study ALOS PRISM Image Pair Level 1B2 nadir and backward Spatial resolution 2.5 m 20071023 (acquisition date) Topographic map Scale 1: 50,000, contour interval 20 m, coordinate system: UTM /WGS 84 2001 -Used for collected data - gained from RTSD

8. 8 Ground Truth The form of Ground truth for collecting data. Date & Time: 14 November, 2007 Serial No. 53 Code of Point on Map: 670 Code of Point on image : 1 UTM/ WGS 84 GPS Coordinates Lat/ Long GPS Coordinates 4971121906530 17º 14' 37.82″N 98º 58' 22.19 ″ E GPS Altitude : 248 mMap Altitude : 240 m No. of Satellites: 8 Description ( on the map) : The intersection of road and right edge of Bhumibhol Dam Terrain type : Near the right edge of Bhumibhol Dam and medium terrain Remark : This cross is clear on both map and image Located on Ban Wang Khai – Song Khaw, Sam Ngao district, Map Sheet: 4843 III

9. 9 Ground Truth Cont’d Ground truth for collecting data.

10. 10 Methodology DEM Generation Accuracy Assessment Result ASTER ALOS PRISM DEM Validation ASTER DEM ALOS PRISM DEM Fused DEM + Locational Error Profile Curvature Check Points Mountain Area Flat Area Water Area

11. 11 Methodology Cont’d Objective 1: To fuse DEM from ASTER & ALOS PRISM satellite images ASTER DEM ALOS PRISM DEM Fused DEM GCPs Selection Tie Points Selection Triangulation DEM Generation ASTER Images Ground Truth Data ALOS PRISM Images Data processing

12. 12 USGS DEM Elevation range Low: 30 m High : 1931 m

13. 13 ASTER DEM Elevation range Low: 58 m High : 1086 m

14. 14 ALOS PRISM DEM Elevation range Low: 135 m High : 1625m

15. 15 Fused DEM Elevation range Low: 58 m High : 1086 m

16. 16 Methodology Cont’d Objective 2 : To evaluate the derived DEM for suitability of terrain surface application 1. comparison of the drainage network from these DEM

17. 17 Drainage networks Referenced - USGS Referenced - ASTERReferenced - ALOSReferenced - Fusion All Drainage networks Referenced Data

18. 18 Locational Error First step: line buffering. Perform a buffer operation on the line data sets X, using a buffer size, ε, which should be significantly larger than the geometric accuracy measure found for the data set X. Second step - overlay. Perform an overlay of the two line-polygon overlays: Overlay Xε with Q, resulting in the new mixed data sets as XεQ. Third step: statistics. Statistics is run to determine completeness Length (Q inside Xε ) Completeness (X ) = Length (Q)

19. 19 Methodology Cont’d Objective 2 : To evaluate the derived DEM for suitability of terrain surface application 1. comparison of the drainage network from these DEM 2. comparison of the terrain relief and Profile Curvature

20. 20 Terrain relief & Profile Curvature - Linear error represents the accuracy of the vertical and the horizontal position. - Differences of profile curvature between DEMs are displayed as linear features Derived DEMReferenced DEM Result Comparison

21. 21 Methodology Cont’d Objective 2 : To evaluate the derived DEM for suitability of terrain surface application 1. comparison of the drainage network from these DEM 2. comparison of the terrain relief and Profile Curvature 3. comparison of the elevation of the derived DEM with the check points

22. 22 Comparison of the elevation of the derived DEM with the check points Defined from the GCPs, Tie points, and user define An algorithm of accuracy evaluation called Root Mean Square Error (RMSE) Where m z is RMSE of elevation δZ i is the elevation differences between the derived DEM and the check points n is the number of check points m z = √ 1 δz i 2 i=1 n _ n ∑ The lower the RMSE, the better the solution

23. 23 The number of Check Points Check points Mountain Area Flat Area Water Area Total USGS DEM 28291168 ASTER DEM 28291168 ALOS PRISM DEM 118726 FUSED DEM 17121039

24. 24 Methodology Cont’d. Objective 3: To verify the result of DEM for several terrain surfaces in term of application suitability. Comparison Referenced DEM ASTER DEM ALOS PRISM DEM Fused DEM Mountain Area Flat Area Water Area Locational Error Profile Curvature Check Points Result

25. 25 1.Introduction 2.Methodology 3.Result of this study 4.Conclusion Presentation Outline

26. 26 Comparison of the drainage network from these DEM

27. 27 Drainage networks (a) (c) (b) (e) (d) a : 1 st Mountain area b : 2 nd Mountain area d : 1 st Flat area e : 2 nd Flat area c : Water area

28. 28 (a) (c) (b) (e) (d) Locational Error USGS ASTER ALOS PRISM

29. ASTER ALOS PRISM USGS Locational Error cont’d (a) (c) (b) (e) (d)

30. 30 (a) (c) (b) (e) (d) Locational Error cont’d

31. 31 Comparison of the terrain relief and Profile Curvature

32. Terrain relief & Profile Curvature Min-200 Max294 Mean-11 SD72.0

33. Terrain relief & Profile Curvature Cont’d Min-204 Max474 Mean29 SD98

34. 34 Terrain relief & Profile Curvature Cont’d Min-0.68 Max0.47 Mean-0.01 SD0.19

35. 35 Terrain relief & Profile Curvature Cont’d Min-182 Max166 Mean3 SD34

36. 36 Comparison of the elevation of the derived DEM with the check points

37. ASTER Min-53.7 Max131.2 Mean17.8 RMSE52.0 USGS Min-19.8 Max81.5 Mean4.8 RMSE22.2 ALOS Min-13.0 Max56.0 Mean5.4 RMSE22.6 FUSE Min-21.0 Max30.0 Mean4.0 RMSE13.2

38. Comparison of the elevation of the derived DEM with the check points Cont’d ASTER Min-59.5 Mean-25.4 Max29.1 RSME35.7 USGS Min-27.2 Mean-1.4 Max37.0 RSME12.8 ALOS Min-11.0 Mean5.7 Max37.1 RSME17.2 Fuse Min-47.6 Mean-7.8 Max37.0 RSME26.3

39. 39 Comparison of the elevation of the derived DEM with the check points Cont’d ASTER Min-61.5 Mean-11.6 Max60.3 RSME35.8 USGS Min-24.7 Mean-9.4 Max34.4 RSME19.2 ALOS Min-30.0 Mean-1.3 Max65.0 RSME31.7 Fuse Min-44.0 Mean-14.8 Max19.4 RSME23.4

40. 40 Result MinimumMaximumRMSEGCP USGS DEM -27.281.518.868 ASTER DEM -61.5131.343.168 ALOS PRISM DEM -30.065.023.726 FUSED DEM -47.037.021.639 Comparison of the elevation of the derived DEM with the check points Cont’d

41. 41 1.Introduction 2.Methodology 3.Result of this study 4.Conclusion Presentation Outline

42. - The quality of ALOS PRISM DEM result is fitted to the referenced DEM. -The drainage networks of ALOS PRISM are likely fitted to the referenced dataset. -ALOS PRISM DEM at finer resolution present more detailed features. -Fused data are more useful for the lack of data and the damaging terrain surface. Conclusion

43. Recommendation for Further researches - Satellite Image should be free cloud for DEM generation -The quality of DEM result depend on the number of GCPs -- User must concern the source of data to generate DEM. -- Apply to use in other area.

44. THANK YOU VERY MUCH