If you work with DEMs, I have a question.

Can the technology used for the data see thru trees and water? By which I mean, if the DEM includes a heavily forested area and a lake, does the DEM show the treetops or the ground? The lake bottom or the water's surface?

iirc it used USGS data so it accounts for trees and it represents water depth.

Some of the older formats use the tree line, I had to do a lot of manual editing on my Ffestiniog route because it was tree line. Best is Lidar which does actual ground level regardless of what is on top of it, doesn't do water depth though, leastwise the one I used didn't.