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Would someone be able to give me the stepped process showing how to add building/woodland elevations to an existing DTM raster in ArcMap?

I seek this in order to prepare a surface model for a viewshed analysis.

I have run a viewshed analysis on a series of points using a DTM raster derived from UK OS Terrain 5. This creates the bare-earth model and is working well.

I now need to overlay this with buildings (at 8m) and woodlands (at 15m) from UK OS Open Map Local, and then add this elevation data to my existing Terrain 5 DTM. This is the bit I'm struggling with:

  • Adding the elevation data to the UK OS Open Map shapefiles for buildings and woodland. The method to do this would be to add an extra field in the attributes table and assign the 8m/15m elevation to this field. What field type/properties should the new field have?
  • Converting the shape file to a raster dataset using the Polygon to Raster tool on each raster created.
  • Merging with the existing Terrain 5 DTM using the Raster Calculator tool. How do you assign the cells with no trees/buildings a value of '0'?

I've seen the question answered for QGIS but not ArcGIS Desktop.

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If I have understood you correctly I think this is fairly straightforward.

Add a new field to the attribute table of your building and woodland shapefiles, I would call it elevation. Use Field Calculator to assign the value of 8 and 15 respectively.

Use the Polygon to Raster tool on each to convert them to rasters. enter image description here

Value field is your elevation attribute. The Cellsize option allows you to point to your existing raster and use that as a template. The new rasters you make will then match up.

So now you have 3 rasters: Existing, Buildings and Woodland. You can now simply add them together using the Raster Calculator tool.

  • That's great, and looks like the exactly what I need. Thanks. Would you be able beak the process down into a few extra steps, so I can see what needs to be input in the tools at the different stages? For examples, when I add the new elevation field to the attributes table for woodland/trees, what type and field properties should it have? It outputs a raster but the viewshed fails when running it. Many thanks. – mike1983 Nov 6 '19 at 11:45

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