Presentation by Arjen Haag (Deltares) at the Symposium Earth Observation and Data Science, during Delft Software Days - Edition 2017. Thursday, 2 November 2017, Delft.

1. Delft, 02 November 2017 Arjen Haag
From space to the street
community participation for a high-resolution terrain model
Symposium Earth Observation and Data Science

2. Why?
Modelling / analysing floods in dense, urban environments
• buildings, streets, pavements, culverts, etc.
• elevated surfaces
• thresholds
• complex vertical geometries
• …
The challenge:
• high-resolution terrain models not available globally
• when available, might not capture all required complexity
The solution:
• fusion of best available terrain model with Open Street Map (OSM) and
community participation

3. A quick teaser
Raw Digital Elevation Model (DEM)
Enhanced Digital Surface Model (DSM)

4. Buildings
building at street level
building above street level
building below street level

5. Sidewalks
elevated sidewalks
sidewalks at street level
no sidewalks

6. Other structures
Canals, rivers
Complex vertical structures
Ditches

7. The baseline
OpenStreetMap (OSM)

8. Community participation
Project in Dar Es Salaam, Tanzania

9. Baseline + community participation
http://ramanihuria.org/

10. Elevation (DEM)
Needs improvements for adding urban features:
• resolution
• smoothness
Raw Digital Elevation Model (DEM)
Smoothed DEM

11. DEM – OSM fusion
raw DEM
OSM features
smoothen
filtering
OSM roads OSM buildings OSM waterways
add heights burn depth
processing
add heights smoothed DEM
Digital Terrain Model (DTM)
(as the water flows)
Digital Surface Model (DSM)
(as the crow flies)
processing processing

12. Results
Digital Surface Model (DSM)
Digital Terrain Model (DTM)

13. Current status
• Google Earth Engine (GEE) scripts
• Google App Engine pilot application (http://osm-terrain.appspot.com/)
• will be shared on GitHub (soonish)

14. Challenges
OSM data:
• not always consistent
• buildings (taginfo)
• (try to) use all available OSM keys/tags, grouped together where needed
• does not always contain required parameters
• building levels and/or heights (taginfo)
• find proxies, relate to others, make assumptions…?
• might not contain all features
• underground structures (sewers)
• involve local communities
• find other data sources?
OSM – DEM fusion:
• not a good match between elevation profile and certain structures
• roads (usually) don’t have elevation differences over their width
• straighten roads over their widths