Saturday, 23 May 2020

Digital terrain models help create a picture

The previous blog showed how to effectively portray coastal inundation, as it progresses inland from the encroachment of sea level rise. These were base on 30 m. resolution Digital Elevation Models (DEM) from OS OpenData as explained previously here.

DEFRA's Risk of Flooding from River and Sea - yet another contributor to coastal inundation discussed here - lead me to DEFRA's high resolution Digital Terrain Model data. In the vast catalogue we used DTM and DSM, respectively, digital terrain and digital surface with buildings and trees atop.  Ranging from 25 cm. to 2 m. resolution, they are very large and many-tiled datasets. Mid-range 1 m. resolution is available as a web mapping service, both from  the mentioned DEFRA site, and as Authoritative features in ArcGIS Online as DTM and DSM, with in addition an Elevation rendering.

That resolution is enough to show features at a local scale, that augment what is seen from DEM data. This story map details the portrayal of coastal inundation. Mid section the geomorphology that can be seen from DEMs is then augmented via updates with digital terrain, surface and elevation.




Turn off the lower two layers (toggle in upper left hand corner) to see the Cam River levee at left, the ditches draining the subsea area at centre, and the road following high ground at top & bottom right.

Tip: hit the toggle arrow and leave it to observe even more detailed imagery (may depend on monitor)


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