In August and September of 2013, I spent several weeks in the woods of Poland teaching LiDAR processing with LAStools to four groups of forestry students as part of the ForseenPOMERANIA camp. Wanting to be locally relevant, I switched my usual training data for a 500 by 500 meter tile of LiDAR from nearby forest that I randomly clipped from the massive amount of data that was handed to me. I did not do a test run before the workshop because I trust my algorithms. Imagine the shock when – during my live demo on the first day of teaching – the bare-earth points extracted with “lasground.exe” showed unexpected distortions: large, weird-looking bumps appeared when generating a hillshade with “las2dem.exe” for terrain that was completely flat.
Turns out we found remains of WW II tank positions. We later drove to the site and verified our findings on the ground.
At that time I had generated a larger 6km by 6km bare-earth hillshade of the area which I showed to a local ranger who pointed out the defensive moat that was dug to stop tanks from advancing. It also became clear that the tanks were aiming towards the north-west, hence at Germany, suggesting they were Russian positions. When you follow the direction the line of tanks are pointing at you can find craters and evidence of the German trenches in the hills.
This was in August. On my return in September, I would meet a retired gentleman whose hobby was a variation of geo-caching: finding old German bunkers and pin-pointing their exact GPS coordinates starting from rough locations on old maps available in souvenir shops and historic records. He confirmed that the positions we found were from late WW-II when Russian forces were advancing fast towards the Eastern seaboard of Germany but were digging in whenever encountering pockets of strong resistance. The saga continues here …