This is the presentation given to a delegation of students from Wageningen University (WUR) on Digital Elevation Models

1. February 25th, 2013
© http://www.viewfinderpanoramas.org
Xander Bakker - GIS Team, Grontmij GIS&ICT

2. 2
The digital elevation model represents the bare ground surface
without any objects like plants and buildings
A digital elevation model (DEM) is a digital representation of
ground surface topography or terrain.
A digital elevation model (DEM) is defined as "any digital representation
of the continuous variation of relief over space,“ Burrough, 1986
Digital Elevation Model (DEM) is a grid where each cell is a value
referenced to a common datum (sea level), Aronoff 1989

3. 3

4. 4
In some definitions a DTM is the same as a DEM
DTM is defined as spatial distribution of terrain attributes, a
topographic map in digital format, that not only consist of the
DEM but also slope, aspect and so on… (Meijerink, A. M. J., De
Brouwer, H. A. M., Mannaerts, C. M. & Valenzuela)
What’s more important; be aware that there are different definitions!

5. 5
 Spot elevation

6. 6
 Contour lines

7. 7

8. 8
© http://maps.google.com

9. 9

10. 10
No break lines Soft break lines Hard break lines
Input data
Triangulation
Surface
3D view
© http://www.ian-ko.com

11. 11
© Ramon Hanssen, TU Delft

12. ght etection nd anging
12

13. ght etection nd anging
13

14. 14

15. 15

16. 16
‘Raw’ AHN2 points(DSM) Filtered AHN2 points ( DEM)
Point cloud
TIN

17. 17
ditch
river
tree
road
hedge
farm

18. 18

19. 19
Buildings not in TOP10
are detected
Buildings mainly
covered with NoData
are depicted as well

20. 20

21. 21
Digital Surface Model
Slope
GIS
Buildings footprints
Aspect
Cities

22. 22
© http://www.iabg.de

23. 23
West East
Cundinamarca, Colombia

24. 24
3D
2D

25. 25
bare earth
Soil maps
Soil maps
GeoTOP
GeoTOP

26. 26

27. 27

28. 28
Speed bumps

29. 29
6
7
A
2 4 5
8 9
B
3 10 11
1
Center of the dike

30. 30
1200 km of dike
Evaluate every 0.5 meter
Retrieve 11 heights
> 26 million queries
… from a dataset with 7 billon pixels (30GB)
Read each time only the extent of 1
dike into memory. Hours of processing
time reduced to minutes!

31. 31
height ≥ A
B ≤ height < A
height< B
Insufficient data
No Data

32. 32
More than 1.5m, AHN2 > A More than 70% NoData
AHN2 < B
Insufficient data, less than 70% NoData, More than 1.5m, B <= AHN2 < A
but no 3 consecutive points with data

33. 33
height ≥ A
B ≤ height < A
B-10cm ≤ height < B
B-20cm ≤ height < B-10cm height ≥ A
B-30cm ≤ height < B-20cm B ≤ height < A
B-40cm ≤ height < B-30cm height < B
height < B-40cm Insufficient data
Insufficient data No Data
No Data

34. 34
Sections of 100m
DEM
Dike center line Cross profile
H100min
Standard profile 3D dike profile

35. 35

36. 36
Standard profiel
after iteration
H100min
Standard profile
before iteration

37. 37
Z
X
Y
First result
Second result before correction
after correction
with better position

38. 38

39. 39

40. 40

41. 41
More information about LAStools:
https://twitter.com/#!/LAStools
http://www.cs.unc.edu/~isenburg/lastools/
http://www.linkedin.com/groups/LAStools-4408378
http://www.facebook.com/LAStools

42. 42

43. 43

44. 44

45. http://twitter.com/#!/XanderBakker
http://nl.linkedin.com/in/xanderbakker
Xander Bakker
Senior GIS Advisor
Xander [DOT] Bakker [AT] Grontmij [DOT] NL
http://software.grontmij.nl
Grontmij Netherlands BV :: GIS & ICT – GIS Team :: http://www.Grontmij.com :: +31 30 220 79 11