0

I have 6 species distribution maps. These species are modelled under certain climatic conditions. As a result, I have 6 raster maps. I would like to obtain a map that shows the richness of these 6 species on the same map.

I believe this can be done by converting raster maps to presence or absence maps. Then add the maps and then obtain the wealth value of each species at each point. I would like to reflect that on a map with a wealth scale of 0 to 6.

1
  • 1
    This is a whole workflow you're asking about, and thus rather hard to answer correctly. I suggest you break the whole workflow down to parts, maybe get personal help from an experienced colleague or superior. Then research each task you will have to accomplish, try what you found, and return to us with specific questions if you are stuck at a specific point in your workflow.
    – Erik
    Nov 18, 2020 at 9:02

1 Answer 1

3

I may suggest a couple of workflow according to your QGIS version.

Personally I prefer Greater than frequency tool, which keeps me from reclassifying each of the input distribution maps.


Classic approach (prior to QGIS 3.16)

This is the workflow what you have described.

  1. Reclassify your distribution map (continuous values) into binary ([0 or 1]) raster. Several tools are available, such as Reclassify by table.
  2. Add the maps using Raster Calculator.

QGIS 3.16

There is Greater than frequency tool in the QGIS Processing Toolbox > Raster Analysis. This tool outputs the frequency (number of times) the values of an input stack of rasters are greater than the value of a value raster. (I wish we could provide the threshold value as a constant, but it has to be a raster).

  1. Create a constant raster by Create constant raster layer tool (in Processing Toolbox > Raster creation). In your case, the constant value needs to be Zero.
  2. Start Greater than frequency and select the constant raster (all zero) as Input value raster. Also select all your 6 distribution maps in the Input raster layers.

enter image description here

enter image description here

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

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