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Is it possible to compare a point shapefile with a DEM raster in which the Aspect tool has been applied?

I am reading about Overlay Analysis but cannot find a definitive answer.

The attached photo is an example of my point dataset (enlarged black dots) shown in front of the study area with Aspect applied. I would like to see how the shapefile is distributed by aspect (e.g., How many points are on a south-facing aspect, how many on a southwest-facing aspect, etc.). With over 200 points, I am trying to avoid doing this manually. I am using ArcMap 10.3.

Example of dataset (shown in black dots) against portion of study area with Aspect shown

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You would want to use the Extract Values to Points tool (if you have the Spatial Analyst extension). The result would be a new field in a new point layer that dictates the aspect value at that particular point. From here, you could quickly determine the aspect distribution of your points.

A recommendation: I would smooth out the DEM first. If (by chance) your point lands on an abnormal bump in the terrain, you might get a false impression of the overall trend of that slope.

  • Thank you very much! Extract Values to Points worked like a charm. The DEM has been frustrating to deal with. I ran and re-ran the merge process numerous times, changing various aspects along the way to see which one worked best. The one I went with wasn't perfect (none were), but it had the least amount of irregularities. Is there a simple way to "smooth" out a DEM after it has been created? – SpencerL Aug 28 '17 at 20:11
  • There is also the Sample tool resources.arcgis.com/en/help/main/10.2/index.html#//… which I find useful. One or more rasters can be the input and points as In Location Data. Output is a table which can be joined to your point features either temporarily (with Add Join) or permanently (with Join Field). – Michael Stimson Aug 28 '17 at 20:52
  • @SpencerL that might be a great question to post to the site as a separate question! Glad I could help (feel free to hit that checkmark!) – Map Man Aug 29 '17 at 13:12
  • @MapMan Great suggestion, I'll create a new question now :) – SpencerL Aug 29 '17 at 14:33
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overlay is a set of tools for vector analysis (vector with vector), so it will not work for vector and raster.

However, iy you have "spatial analyst" extension (which you have if you made aspect from raster DEM in ArcGIS), you can use the tool called "extract multivalue to point" in order to add a new field with the values of the underlying raster(s). Alternatively, you could reclassify the raster into a set of major aspect values (e.g. 0-45;45-90 etc), then convert this reclassified raster into vector polygons and finally use intersect tool between points and polygons.

PS: I prefer extract multi value to point instead of extract value to point, because it does not create a new shapefile.

  • Thank you very much for the help! The Extract Values to Points tool seemed to work, but I will remember Extract Multivalue to Point tool in case I need everything to be in one shapefile. – SpencerL Aug 28 '17 at 20:18

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