This presentation shows how AHN2 LiDAR data was used to depict buildings and determine object heights

1. 1 Extract buildings from AHN2 data Xander Bakker Grontmij Team GIS

3. A ‘Clutter’ holds base data on surface including object heights classification

4. Grontmij has provided the clutter dataset in 2004

6. Using various datasets; NKNL (plans for urban expansion), W&B (population data), aerial photography (Bing) urban expansion areas were identified

7. Previous updates were based on AHN1 (5m Min and Max grids)

9. Return time defines surface height

10. Multiple returns possible

11. AHN2: 30 points per m²

13. 6 AHN2 products Pricing / km² (< 1.250 km²) € 56,- € 56,- € 28,- € 28,- € 28,- € 12,- Pricing / km² (<= 15.000 km²) € 28,- € 28,- € 14,- € 14,- € 14,- € 6,- Pricing / NL (> 15.000 km²) € 455.000,- € 455.000,- € 227.500,- € 227.500,- € 227.500,- € 97.500,- Data contains Bare Earth Bare Earth + Objects Bare Earth Bare Earth Bare Earth + Objects Bare Earth Product Filtered laserpoints Unfiltered laserpoints 0.5m grid filtered 0.5m grid filtered + interpolated 0.5m grid unfiltered 5m grid filtered The purpose of AHN2 is to get a highly detailed representation of the bare earth (maaiveld). Objects (houses, trees, etc.) are filtered.

14. 7 LASER points Unfiltered points Filtered points Point cloud TIN

15. 8 Filtered grid 0.5 m/pix (Bare Earth) Not Interpolated Interpolated

16. 9 Unfiltered grid 0.5m/pix The only raster AHN2 product that holds information on objects…

17. 10 Profile unfiltered grid 0.5m/pix ditch river tree road hedge farm

18. 11 LIDAR Analyst v4.2

20. Attributed data

21. Extraction of buildings, trees and forest

22. Enhancement tools

23. Batch processing

24. Complex parameters

25. Parameters vary per area

26. Long processing time (estimated 20 minutes CPU per AHN2 subunit)

27. Manual corrections required

29. 14 ArcGIS 9.3 Spatial Analyst / ArcObjects Simple Case : Buildings exist in TOP10 TOP10 buildings Region group Zonal max Zonal max – Focal min AHN2 raster Focal min

31. Buildings contain mainly NoData

33. Size

34. Gradient

36. NDVIOnly works for small areas!

41. 22 Calculate object heights

43. Buildings mainly covered with NoData are depicted as well1 before 2 3 1 after 2 3

45. Processing time for 1 subunit is 3 min.

46. Batchprocessing

47. Good alternative for lacking data in TOP10

48. Highways need to be filtered out

49. Some buildings not detected

53. Many exceptions difficult to account for at forehand

54. AHN2 order process does not indicate percentage of NoData per subunit

55. AHN2 data has not been thoroughly checked (subunits entirely filled with NoData, wrong resolution, no crd sys)

56. TOP10NL is missing a lot of buildings (is not up-to-date)