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Lars Arge, University of Aarhus Herman Haverkort, TU Eindhoven Andrew Danner, Swathmore College PowerPoint Presentation
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Henrik Blunck University of Aarhus. 8. 72. 9. 7. 7. 75. 4. 71. 5. 74. 73. 3. 6. 25. 1. 24. 21. 2. 2. 27. 26. 22. 23. Watershed decomposition . Digital elevation map. Pfafstetter labels. USGS (manually). Overlay. Lars Arge, University of Aarhus

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Presentation Transcript
slide1

Henrik Blunck

  • University of Aarhus

8

72

9

7

7

75

4

71

5

74

73

3

6

25

1

24

21

2

2

27

26

22

23

Watershed decomposition

Digital elevation map

Pfafstetter labels

USGS (manually)

Overlay

Lars Arge, University of Aarhus

Herman Haverkort, TU Eindhoven

Andrew Danner, Swathmore College

Norbert Zeh,, Dalhousie University

  • TerraSTREAM: Pfafstetter Labeling
  • Watershed decomposition
  • Watershed decomposition is a fundamental task in terrain analysis
  • Watershed of a river = area which drains to the river
  • Terrain dividable into (hierarchy) of watersheds
  • A river’s watershed can be subdivided into the watersheds of the river‘s tributaries
  • Pfafstetter labels
  • Identify main river
  • Find the 4 largest tributaries (orange)
  • Label tributaries (even) and interbasins (odd)
  • Recursively label all tributaries and interbasins
  • “Sanity check”: Pfafstetter decomposition “matches” manually
  • constructed watershed decompositions

I/O-efficient algorithm

  • Modern terrain data is massive

 I/O-efficient Pfafstetter labeling algorithms needed

  • We develop I/O-efficient algorithm by exploiting
    • Terrain decomposable into rivers, i.e. into tributaries
    • Tributaries form a tree
    • Rivers can be labeled individually
    • Label prefixes can be “forwarded” to tributaries

I/O-efficient algorithm

Watershed decomposition

Pfafstetter labels

Current and future work

  • Current and future work
  • Watershed queries: Retrieval (and decomposition) of watershed for individual user-specified location
  • Meaningful labeling along coast lines, e.g., label the coastal watersheds independently or as tributaries of the “coastal river”

+

=

Subdivision of a watershed

Independent costal watersheds

Connected coastal watersheds

References

[1] L. Arge, A. Danner, H. Haverkort, and N. Zeh. I/O-Efficient Hierarchical Watershed Decomposition of Grid Terrain Models. In Proc. 12th Intl. Symp. on Spatial Data Handling, SDH, 2007.

[2] K. L. Verdin and J. P. Verdin. A topological system for delineation and codification of the Earth's river basins. Journal of Hydrology, 218, 1-12, 1999.

Integration into TerraSTREAM

MADALGO – Center for Massive Data Algorithmics, a Center of the Danish National Research Foundation