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Gathering Different Elevations for 3D Buildings from DEM

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Gathering Different Elevations for 3D Buildings from DEM

The 3D buildings were extracted from LiDAR data collected by the City of Calgary but there were no attributes and the type of file of 3D buildings was a geodatabase. Based on what happened with flooding in 2013 the City of Calgary inspectors wanted to know in the event of future flooding, the lowest elevation of the houses or buildings to inspect right away to determine if the building is affected or not by the flooding. The elevations gathered were:
1. The lowest ground elevation of the building (x, y and z).
2. The highest ground elevation of the building (x, y and z).
3. The highest elevation of the building (x, y and z).

These elevations were calculated for more than 400,000 buildings in the City of Calgary and the whole process to gather the elevations were processed from 2 different workbenches, one using the DEM to extract the ground elevations and the other workbench was using the real 3D building elevations to calculate the highest point from every single building.

The 3D buildings were extracted from LiDAR data collected by the City of Calgary but there were no attributes and the type of file of 3D buildings was a geodatabase. Based on what happened with flooding in 2013 the City of Calgary inspectors wanted to know in the event of future flooding, the lowest elevation of the houses or buildings to inspect right away to determine if the building is affected or not by the flooding. The elevations gathered were:
1. The lowest ground elevation of the building (x, y and z).
2. The highest ground elevation of the building (x, y and z).
3. The highest elevation of the building (x, y and z).

These elevations were calculated for more than 400,000 buildings in the City of Calgary and the whole process to gather the elevations were processed from 2 different workbenches, one using the DEM to extract the ground elevations and the other workbench was using the real 3D building elevations to calculate the highest point from every single building.

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Gathering Different Elevations for 3D Buildings from DEM

1. 1. Acquiring elevations for 3D Buildings Jairo Castillo The City of Calgary
2. 2. 2013 Calgary Floods
3. 3. In case of future flooding, the inspector can access building information that identifies where the minimum elevation of the building is to check if the building has been affected. This is important as inspectors often only view the front of residences and buildings.
4. 4. How 3D Buildings were created?
5. 5. LiDAR unclassified
6. 6. LiDAR Classified
7. 7. Buildings as dgn file
8. 8. LiDAR and Buildings
9. 9. 3D Buildings have unique Structure ID attributes and the project was to calculate three Elevations per building (Rooftop, Ground Min Elev, and Ground Max Elev)
10. 10. It was a challenge to process and find heights of more than 418,000 individual buildings in the City of Calgary
11. 11. Points were generated for every vertex on the multipatch file
12. 12. Multipatch Shapefile: Consists of a number of surface patches. “ESRI Shapefile Technical Description” July 1998 . ESRI <http://www.esri.com/library/whitepapers/pdfs/shapefile.pdf >
13. 13. Rooftop Elevation Workbench
14. 14. Problem: The Minimum Elevation of the Building data does not fit the surface of the ground.
15. 15. Part of the building is in the ground.
16. 16. Solution: 3D Buildings have been transformed as Footprint (2D) features Key Transformer: SurfaceFootprintReplacer
17. 17. The footprint was densified every metre and the vertices were extracted and superimposed over the DEM.
18. 18. StatisticCalculator extracts a min and max value in Z for every building
19. 19. FeatureMerger selects the minimum and maximum elevation
20. 20. The workbench creates a point where the ground has the maximum elevation along the footprint of the building.
21. 21. The workbench creates a point where the ground has the minimum elevation along the footprint of the building.
22. 22. Final Attribute table
23. 23. Ground Elevation Workbench
24. 24. Thank you! Jairo Castillo jairo.castillo@calgary.ca The City of Calgary