I have one population raster showing how many 'people' are in a grid cell (i.e. population count per cell)

And I have another raster for water available per cell.

I want an output raster that is classified based on how much water is available for 1 person in a cell. for example:

If 1 person has 1000 cubic meters of water for matching cells in the input rasters, that grid cell in the output raster will have a value of 1.

How do I achieve this in arcmap 10.2. I have the spatial analyst tool activated.

I feel this is a conditional query but I don't know how to do it. It should be something like this in english:

If water raster has cell values of <500, 500-1000, 1000-1700 and >1700 for each 1 person in a cell then output raster will record values of 1, 2, 3 and 4 respectively for cells with these values.

The issue is that population raster shows total number ofpeople in a cell, how do I factor this into the query which is looking at what is available per person.

  • what is the spatial resolution of each raster ?
    – radouxju
    Dec 1, 2014 at 19:08
  • Thank you for your reply. They are all 30 minute (0.5 degree) resolution on WGS 1984 Coordinate System Dec 1, 2014 at 19:24
  • You need to divide the raster population by the water availability (you can use the Raster Calculator tool, i.e. Raster Pop / Raster Wa) and then on the resulting output use the Reclassify tool to define your classes Dec 1, 2014 at 19:47
  • below radouxju says water/population. which one? Dec 1, 2014 at 19:51

1 Answer 1


You could use the raster calculator to have the amount of water per person

Con("population" > 0, "water"/"population" , -1)

then you can use "reclassify" to set your threshold.

  • Thanks radouxju, GianlucaF says population/water. Which one? Dec 1, 2014 at 19:52
  • Thanks again radouxju! water/popuation is what I need to do Dec 1, 2014 at 20:01
  • I ran the raster calculator but I'm having nodata in some cells where there should both raster are overlapping Dec 1, 2014 at 20:20
  • 1
    it could be due to a division by zero (no population). I've changed the code to avoid this issue.
    – radouxju
    Dec 1, 2014 at 21:39
  • Hi radouxju, the raster calculator provided data this time. but attempt to classify still not working properly, it is not displaying the new integer values. Dec 1, 2014 at 22:15

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.