I am trying to find areas near a series of roads that are withing 500 ft of the road, and have a change in elevation of +50 ft. I have been provided a 2 ft contour of the area, and a centerline layer for the roads in question. My thought process was to intersect the roads and topo, to create points which I could then create the 500 ft buffer from. From there, I am not sure how to proceed and select from this the areas of elevation im looking for

  • What is the file type of the contours? – Map Man Feb 17 '17 at 15:32
  • It is a File Geodatabase Feature Class. – Andrew Feb 17 '17 at 15:38

I would:

  1. Make a raster dtm from the contours
  2. Use the raster to make the road line 3D
  3. Buffer the roadline to make a 500ft 3D Buffer in the same resolution as the dtm
  4. Subtract the road-buffer raster from the dtm raster
  5. Set all values < 50 in the result to NoData.
  6. Convert raster to points.

You now have a point dataset with an attribute that shows how much more than 50ft they are above the road (in a perpendicular distance). There will be other approaches but this one springs first to mind.

  1. Convert contours to DEM (Topo to Raster)
  2. Change DEM to integer type (Int)
  3. Run Euclidean Allocation, where feature source = roads, input value raster = integer DEM, and set maximum distance to 500'
  4. Raster Calculator: Con("Integer DEM" - "Euclidean Allocation">50,1,0). Results in binary raster showing pixels where difference is > 50' within 500' of the road. Could also output DEM value.

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