topic Re: Point buffer overlap in Geoprocessing Questions

Point buffer overlap

SusanneVogel — Sun, 24 Feb 2013 18:25:03 GMT

I have a map with about 300 data points, and I want to find out how many 'neighbouring' points each point has (within 300 meters). I thought it might be possible to achieve this by creating a buffer around each data point and than counting the number of overlapping buffers. I have made these buffers and used intersect between them, but I have no idea how to find out how many points each buffer overlaps. Maybe it is an easy problem but does anyone have an idea?

Re: Point buffer overlap

DaleHoneycutt — Mon, 25 Feb 2013 16:02:14 GMT

See this blog post More adventures in overlay: counting overlapping polygons with spaghetti and meatballs. It's not exactly what you're looking for, but the section titled "Point in polygon overlay" should be very helpful.

Re: Point buffer overlap

curtvprice — Mon, 25 Feb 2013 17:29:08 GMT

I have no idea how to find out how many points each buffer overlaps. Maybe it is an easy problem but does anyone have an idea?

If you have an ArcGIS Advanced license, Point Distance (with a 300m search distance) will make a table you can then process with Frequency to get the count you want.

Re: Point buffer overlap

SusanneVogel — Tue, 26 Feb 2013 13:08:10 GMT

Thank you for replying! Yes, I have already tried that for a couple of times, and I keep getting an empty attribute table! Do you know what could be going wrong? I thought it was because it might not be possible to do a point distance calculation on only one point data set (as I want to know the distance between points within the same layer)?

Re: Point buffer overlap

DanPatterson_Retired — Tue, 26 Feb 2013 13:11:19 GMT

Is the point data in a projected coordinate system? that matches your desired buffer size?

Re: Point buffer overlap

curtvprice — Tue, 26 Feb 2013 15:39:12 GMT

I thought it was because it might not be possible to do a point distance calculation on only one point data set (as I want to know the distance between points within the same layer)?

The tool does support providing the same point feature class for from and to inputs. I agree you should project your point feature classs to UTM or some other appropriate coordinate system before you run Point Distance so your distances will be in meters.

Re: Point buffer overlap

DaleHoneycutt — Tue, 26 Feb 2013 15:56:36 GMT

You could also use the Spatial Join tool. The Target Features and the Join Features would be the same layer (your point layer). The Join Operation is JOIN_ONE_TO_ONE, the Match Option is WITHIN_A_DISTANCE and your Search Radius is 300 meters. This will give you a new output point feature class where TARGET_FID is the object ID of the input point and Join_Count is the number of points within 300 meters.

Also, for most proximity (distance) calculations, I agree that projecting your data to a projected coordinate system such as UTM is usually a good idea.