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I'm using ArcGIS 10.2.2. I've been running some viewsheds using DTM files from EDINA Digimap and data that I've imported using .csv files. These files only contain the X Y details and a code for each site. The DTM files were 'stitched' together using the 'Mosaic to New Raster' tool in the ArcToolbox.

Out of nine that I've run, six viewshed's show no visibility to the south east.

I've checked the following.

  • I've run the viewshed again just using the one square and nothing else. That was fine.
  • I've run it using the mosaic to new raster on the NE, SE, SW and NW cells as one. This was fine.
  • I then ran it again using the mosaic to new raster but this time included the four cells below, so its not 74 NE, SE, SW and NW 75 NE, SE, SW and NW all stitched together. This showed the same problem with no view to the south east.

Has anyone had any issues like this before? It seems odd (to me anyway).

  • Are you sure this result is incorrect? Especially when either (a) the viewpoint is not elevated above the DEM and/or (b) the DEM is noisy and/or (c) the terrain is rugged, whole sections of the view can appear to be cut off. The problem in cases (a) and (b) lies with the DEM and the parameters supplied with the viewshed, but do not reflect problems in the viewshed algorithm itself. – whuber Sep 5 '14 at 22:51
  • Yes, I'm pretty sure its incorrect. I've been out at these sites and know what I was expecting. The DTM does show a decrease in height too, so its not as though some information the DTM files have been lost during the mosaic phase. – AJames Sep 5 '14 at 22:58

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