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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
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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.

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  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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