How to compare two binary raster to find out the difference/change?

[Syed Amir Manzoor]

Hi,

I have two raster ouputs from Maxent (current climate scenario SDM vs Future Climate Scenario SDM) and I'm interested in making a third raster map showing the areas with increased or decreased risk of invasion (of the species under study). One of doing it, as I've tried it, is in SDMToolbox in Arcgis. But it either keeps showing error or the result folder are empty if it runs properly. Is there any advice on using SDMToolbox especially in context of avoiding key errors? (I've gone through the tutorial very well. I'd appreciate if you can share something from your personal experience or may refer to any sources other than tutorial). 

Also, other than SDMToolbox, is there a way of comparing binary SDM's or to compare SDM's with multiple classes? (like 4 habitat classes) or so?

I thank you for your time.

Amir

[Jamie M. Kass]

Not sure exactly what product you want, but you can do raster algebra with the "raster" package quite easily in R. Example:

library(raster)
a <- raster("path to raster A")
b <- raster("path to raster B")

a + b. # raster sum
a - b # raster difference

There are also easy tools for this in ArcGIS and QGIS.

Jamie Kass
PhD Candidate
City College of NYC

[tdonald]

Hi

tell me the tools i can use in ArcGis and Qgis, and how to use it

thanks

[Jamie M. Kass]

Not sure about QGIS, but in ArcMap you can use the Raster Calculator.
http://desktop.arcgis.com/en/arcmap/10.3/tools/spatial-analyst-toolbox/building-expressions-in-raster-calculator.htm

Jamie

[Žan Kuralt]

Hey!

In QGIS you should first vectorise your binary rasters (Raster -> Conversion) and then use the "Difference" function (Vector -> Geoprocessing tools) to get the desired area.
You can then easily rasterize the vector layer back.


Cheers,
Žan