LiDAR wavelengths are returned at various depths from within the forest canopy. In order to get a return on the ground you simply filter the returns down to the

LiDAR wavelengths are returned at various depths from within the forest canopy. In order to get a return on the ground you simply filter the returns down to the last value. Sometimes however you want to keep the other returns and so you filter the values down to say 10% of all returns from a given depth, with a constraint between the depths of say 10cm so that you can see the density of the layers.