These are two python GIMP plug-ins to resacle and juxtapose images of the same area. To use them put the .py file in the GIMP plugin folder see this guide for more info.
#Mac OS See this guide
cd /Applications/GIMP-2.10.app/Contents/Resources/lib/gimp/2.0/plug-ins/
chmod 755 CompareImageAdva.py
The two images must be registered before with an external tool (see image registration).
In some case (e.g. when you use GIS software) exported images are registered but don't have the same scale.The first plug-in simply center an rescale the images so the can be compared with the second plug-in.
It basically allows to place images side by side and eventually automatically palce a marker (arrows, circles, etc. etc.) in every images in the same point over all the images.
Click on the image to see a youtube tutorial.