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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.

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4
  • what is the spatial resolution of each raster ?
    – radouxju
    Commented 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
    – veesilouette
    Commented 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
    – Gianluca Franceschini
    Commented Dec 1, 2014 at 19:47
  • below radouxju says water/population. which one?
    – veesilouette
    Commented Dec 1, 2014 at 19:51

1 Answer 1

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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.

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6
  • Thanks radouxju, GianlucaF says population/water. Which one?
    – veesilouette
    Commented Dec 1, 2014 at 19:52
  • Thanks again radouxju! water/popuation is what I need to do
    – veesilouette
    Commented 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
    – veesilouette
    Commented Dec 1, 2014 at 20:20
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    it could be due to a division by zero (no population). I've changed the code to avoid this issue.
    – radouxju
    Commented 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.
    – veesilouette
    Commented Dec 1, 2014 at 22:15

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