anyway you may do it all - exception of cropping sketches - in Therion. And main advantage is you’ll have all sketches in scale in correct places according stations.

And here is an editor which is enough to edit .png files for Therion including erraser: https://pixlr.com/e/#editor

22. 6. 2021 v 15:40, Bill Gee <bgee@campercaver.net>:

Thanks for the hints! I was able to get several sketches combined in GIMP. Looking at the result, it is very obvious that much more work is required in the cave. There is a huge hole in the middle which has no detail at all. There are missing walls in several places.

My plan now is to print the combined sketches on a piece of paper. The next survey trip I will draw more on it. That will then become the background in Therion.