You can use SAR higher up than LIDAR, because SAR is not affected as much by cloud cover. However, SAR is less detail oriented than LIDAR.
Interesting. Because of detail, it yields spectacular results. I participated in one of the first public trials of GPR in 1982. It wasn’t much different looking that what you see dragged along the ground today, but it was absolutely amazing in its day. Before we used it in the field on an Excavation, we dragged it across a quiet, little used blacktop hiway in Texas.
I didn’t think much of it until I saw the image of a tree truck, with a perfect root system, under the hiway. I don’t remember the gentleman’s name that demonstrated it for us, but he was a NASA engineer. Apparently it was developed as part of the moon investigation effort.