topic Re: Count number of pixels overlapped by points. in Data Management Questions

Count number of pixels overlapped by points.

mariagarcia — Tue, 18 Dec 2018 16:30:12 GMT

I got a raster classified in four areas and a series of points. I would like to count the number of pixels that are overlapped by the points, I do not need to extract, just to count them, for each raster class. There could be more than 4 points in a pixel. I just need to know how many pixels got points on them?

I tried the 'extract by points' tool , but it only allows me to select one point??

Is there a tool in ESRI to do this? or a two stage process?

I use ArcMap 10.3 and I got quite a few licences such as Spatial analysis etc.

thanks for any advice.

Re: Count number of pixels overlapped by points.

DanPatterson_Retired — Tue, 18 Dec 2018 18:24:00 GMT

arcmap or pro don't do pixel counts, they can do 'zonal', 'local' or 'neighborhood' statistics. So if each pixel was its own zone, then it could be done, but if each pixel is part of a zone, then you won't get the information you need.

Local statistics would require a different formatting of your inputs

Re: Count number of pixels overlapped by points.

JimCousins — Tue, 18 Dec 2018 20:03:47 GMT

There are 2 tools in Spatial Analyst Tools >> Extraction.

1 is the tool you tried, and another is Extract Values to Points - Try that one. It will return the raster value that the point falls within, and then you can run a summary on the raster value attached to the points, and get your counts.

Best Regards,

Jim

Re: Count number of pixels overlapped by points.

ModyBuchbinder — Wed, 19 Dec 2018 06:06:37 GMT

I would try to create a "count" raster using the CON in raster calculator.

something like

outCon = Con(IsNull("ras"),0, 1)

Once you get the "count" raster you can use extract by point.

Have fun

Re: Count number of pixels overlapped by points.

mariagarcia — Wed, 19 Dec 2018 14:59:09 GMT

thanks I will research on this.

Re: Count number of pixels overlapped by points.

mariagarcia — Wed, 19 Dec 2018 15:04:39 GMT

thanks for your reply. I had tried this and I summarized by the raster value. It is not really accurate as there could be two pixels with the same value, but the closest I got.

thanks

Re: Count number of pixels overlapped by points.

mariagarcia — Wed, 19 Dec 2018 16:36:18 GMT

thanks for your reply. I had tried this and I summarized by the raster value. It is not really accurate as there could be two pixels with the same value, but the closest I got.

thanks