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Given a shapefile layer of 5-ft interval topography contour lines overlaid on google earth, I could, using the Ruler tool and some simple arithmetic, calculate average percentage grade numbers for a sample of points in an area.

What are some ways I could do calculations that like using a GIS program to ultimately generate a heatmap of grade estimates for an area? In terms of functionality, I suppose it would segment out the spaces between contour lines by some predefined length (or other method based on variation...), calculate the average grade between those lines, and output a number, which would then be used to color code each given polygon.

I have a fair amount of GIS scripting experience (ruby/rgeo/geos) and could probably cook up a custom solution for this, but given my experience in the GIS space by now, I have come to learn that it is best to see what's out there already in terms of pre-packaged solutions and/or established algorithms (for example, Hexagonal tessellations rather than cubes) before breaking out the custom scripting.

  • What you are talking about called interpolation, you might want to use triangular irregular network or multiple interpolation methods eg inverse distance weighted. I wish you best of luck to 'cook something' quickly. As far as I know topo to raster in Arcgis is the best when dealing with contours and it is anything but simple. I'd be careful stating fluency with GIS. Scripting, perhaps.. – FelixIP May 21 '17 at 9:34
  • @FelixIP Yes, scripting, heavily reliant of abstractions, C libraries mostly, to do the heavy lifting. But that's all software development really is in my world at least. – boulder_ruby May 21 '17 at 10:42
  • Google earth now does some pretty amazing stuff with its "generate elevation profile" feature, over lines, and who knows what else – boulder_ruby Jun 2 '17 at 3:20

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