I've read articles like these https://www.nationalgeographic.com/history/article/maya-laser-lidar-guatemala-pacunam and wanted to understand what's going on here. My understanding is the lidar would mostly bounce off of the canopy but to create maps like the ones in the article you would need to generate height maps from below the canopy.
Is there some sort of filtering of the point cloud that's going on? Do enough of the pulses reach the ground and back that meaningful data can be collected? I'm just wondering how surveyors able to generate meaningful maps of what what the canopy is hiding and make these amazing discoveries?