I have run a viewshed analysis on a single point using a UK OS Terrain 5 DTM which has worked fine. I now need to perform the same analysis but with buildings and woodlands taken into account.
I've have OS Vectormap District data for both the buildings and the woodland areas which are shape files and want to add generic height values to each of these. Am I right in thinking that this is the process?
- Add 'Height' attribute field of 5 to buildings and 15 woodland layers (Conservative values)
- Convert both polygon layers to rasters
- Use the raster calculator to add the two new rasters to the existing DTM (I'm not familiar with this so a step by step process would be very useful). When running this it's masking out the areas that are not woodland or buildings (presumably NoData areas). How do you assign a value of 0 to these NoData areas?
- Run viewshed again using new DTM
One final question - how can I avoid the viewshed calculating 'on top' of those features? (i.e. the woodland and the buildings)