Count number of pixels overlapped by points.

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12-18-2018 08:30 AM
mariagarcia
New Contributor II

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.

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6 Replies
DanPatterson_Retired
MVP Esteemed Contributor

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

JimCousins
MVP Regular Contributor

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

mariagarcia
New Contributor II

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

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mariagarcia
New Contributor II

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

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ModyBuchbinder
Esri Regular Contributor

Hi

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

mariagarcia
New Contributor II

thanks I will research on this.

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