Relating Hill-Shading to Terrain Metrics

Patrick Kennelly – LIU Post
James Stewart – Queens University

Transcript

1. Relating Hill-Shading to Terrain Metrics Patrick Kennelly – LIU Post James Stewart – Queens University
2. Relating Hill-Shading to Terrain Metrics ò Background ò Objectives ò Methodology ò Results ò Summary
3. Hill-Shading in GIS Background Objectives Methodology Results Summary
4. Hill-Shading in GIS Elevation Grid Hill-Shaded Grid Background Objectives Methodology Results Summary
5. Point Source Illumination Background Objectives Methodology Results Summary
6. Point Source Illumination Background Objectives Methodology Results Summary
7. Other Illumination Models Background Objectives Methodology Results Summary
8. CIE Sky Models ò  Directional ò  Uniform ò  Overcast ò  Non-Directional ò  Clear ò  Sharp ò  Turbid ò  General (1 – 15) Background Objectives Methodology Results Summary
9. CIE Sky Models Background Objectives Methodology Results Summary Directional Non-Directional Uniform Overcast Sky Point Source Sharp + Diffuse Sharp Clear Day ✔ ✔ ✔
10. Objectives ò  Allow GIS users to hill-shade terrain maps using models in addition to point source illumination. ò  Use well-established sky models in a rigorous manner for hill-shading. ò  Understand which sky models are most useful for various types of terrain or landforms. Background Objectives Methodology Results Summary
11. Methodology Overview Background Objectives Methodology Results Summary
12. PC Application Background Objectives Methodology Results Summary User defined variables: Ø Sky model (from a list) Ø Azimuth (if directional) Ø Inclination (if directional) Ø Sharpness of illumination (if Sharp) Ø Diffuse lighting (if Sharp) Ø Number of points with which to sample the sky
13. PC Application Background Objectives Methodology Results Summary
14. Methodology ò  Begin with large number of sky sample points of equal azimuth spacing for equal increments of inclination. ò  Sky radiance for each sample point is computed. ò  Radiance values of sample points are divided into a given number of standard deviations, each representing a strata. ò  Each stratum allocated approximately the same number of illumination vectors. ò  Illumination vectors iteratively chosen to maximize angular distance from all previously chosen directions. Background Objectives Methodology Results Summary
15. Output List & Python Script Azimuth, Inclination and Weight Weights and sums hill-shaded grids Background Objectives Methodology Results Summary
16. Hill-Shaded Grids Weighted and Summed x W1 x W2 x W3 x W4 x W5 + + + + + Background Objectives Methodology Results Summary
17. Mt. Hood, Oregon Point Source Clear Day Background Objectives Methodology Results Summary
18. Mt. Hood, Oregon Point Source Clear Day Background Objectives Methodology Results Summary
19. Mt. Hood, Oregon Background Objectives Methodology Results Summary Clear Point Aspect m=-0.5072 R2=0.69441 m=-1.0026 R2=0.36791
20. Mt. Hood, Oregon Point Source Overcast Sky Background Objectives Methodology Results Summary
21. Grand Canyon, Arizona Point Source Clear Day Background Objectives Methodology Results Summary
22. Grand Canyon, Arizona Point Source Overcast Sky Background Objectives Methodology Results Summary
23. Grand Canyon, Arizona Point Source Overcast Sky Background Objectives Methodology Results Summary
24. Grand Canyon, Arizona Background Objectives Methodology Results Summary Slope m=-0.0388 R2=0.04274 m=-0.1697 R2=0.09952
25. Grand Canyon, Arizona Background Objectives Methodology Results Summary Elevation m=-0.6517 R2=0.00189 m=9.7655 R2=0.05161
26. Summary ò  CIE sky models can be rigorously implemented in GIS using output from a PC application develop by the authors. ò  Hill-shading with sky models reveals details of terrain that can be lost in shadows, dark shading, or strongly illuminated terrain. ò  Directional sky models preserve the three-dimensional appearance of terrain with predominantly positive relief. ò  Non-directional sky models allow more light to illuminate the depths of dissected terrain such as canyons. Background Objectives Methodology Results Summary
27. Beta Application Download and Additional Information ò  Application download: ò  http://watkins.cs.queensu.ca/~jstewart/SkyLum.zip ò  Upcoming publication: ò  Kennelly, P. and J. Stewart. General Sky Models for Illuminating Terrains. Accepted by the International Journal of Geographical Information Science. DOI: 10.1080/13658816.2013.848985 (not yet activated) Background Objectives Methodology Results Summary