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For my dissertation I have collected point features as coordinates and want to relate their distribution around a lake to elevation to see if there is any pattern/relationship between them.

I have downloaded the 5m DTM file for the location but want to be able to automatically calculate the number of points within each grid square of the DTM but I'm unsure how to do this.

I then want to be able to create graphs from this data of elevation vs. number of points.

As a relative newbie to GIS, I don't have much experience doing what appear to me, to be more complicated processes.

I'm using ArcMap 10.2.2 and I believe I have access to all toolbox functions whether on my laptop or a university computer!

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    Please clarify if @HDR answer is what you are after? I think it more likely that you are interested in general elevation values than the individual DTM cells/ – DMusketeer Oct 7 '15 at 12:24
  • Sorry, been away from internet access for a while! I have now resolved my issue so thank you both for your help, its greatly appreciated! – LMC94 Oct 7 '15 at 16:19
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To clarify, you want to know the number of points that coincide with each cell of the 5 m DTM? If so, I'd try:

  1. convert the DTM to polygon using the raster to feature tool
  2. Perform a join-by-location of the polygon feature to the points. Now each point will be labelled with the ID of the polygon cell it resides in.
  3. Create a histogram of the polygon cell IDs in the point featureclass. This reveals how many points are located in each polygon cell.

Let me know if this is what you're looking for.

  • OP mentioned "elevation vs. number of points." but I think this solution focuses more on individual raster cells than it does elevation which is more likely to be the research question (imo). I would use this method but use the raster value rather than ID's to join. Better yet is probably binning the elevation values - maybe reclassify the raster first? – DMusketeer Oct 7 '15 at 12:21
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    Yeah, I fully see what you mean. My answer focuses on "the number of point withing each grid square". But I fully agree that it'd be more interesting to join to the raster values. If that's indeed what OP is after, I'd recommend using the Extract Values to Point tool. – HDR Oct 7 '15 at 12:29
  • Hi Thank you for your help, I have done steps 1 and 2 but am unsure exactly what you mean in step 3? I'm not sure how to do what you've suggested so if you could give me any more info that would be fantastic and my problem will be sorted! Thanks for you help thus far though! – LMC94 Oct 7 '15 at 13:20
  • Step 3 implies counting how often each grid cell occurs among all your point. However, please confirm first what exactly you're looking for. Are you sure you don't want to extract the DTM elevation value to each point?? – HDR Oct 7 '15 at 13:27
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To pass values from the raster to a point file, use the Spatial Analyst tool, Extract Values to Points.

/r/gis

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