I am currently working on a fantasy map project building the world of Ternia, a project that is designed to create something that is similar to Nicolaus Germanus' Ptolemy world map from 1482 (author died in 1490, so no copyright restrictions). The original map that I am trying to reproduce can be found here:
https://upload.wikimedia.org/wikiped...a_Germanus.JPG

Now I have run in to a few issues regarding getting the right effects applied for the mountains in Inkscape (since mountains were drawn back in the day as lumpy shapes rather than actual hilltops) - the closest that I have managed to get to reproducing the effect that I wanted so far is the "Canvas Edges Matte" effect in Inkscape, using a filter size of 0.015 and detail of 10. The output that I have managed to achieve so far can be found in this link here:
https://photos.app.goo.gl/U9YfVMbAg77EfVSh9
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Is there anyone who is knowledgeable in Inkscape (or can do something similar using GIMP) who can advise me on how to reproduce the mountains as seen in the work of Germanus?

Many thanks, Jakub