Warning of inconsistant echo range (0m)
Created by: cgretler
Dear Team of AMAPVox, Thank you so much for this powerful tool. I have a question regarding a warning in some of my computation. I am working with AMAPVox version 2.0.0 and LAZ-files from ALS-acquisitions. During the voxelisation process, I often get the following warning of inconsistent echo ranges:
2023-06-23 07:53:54 WARN - Inconsistant echo ranges (either interlaid blank echo or distances not monotonically increasing).
Shot 1633470, 4 echoes
origin (2646227.8955, 1266448.9913, 1282.372) direction (-0.3215, -0.1541, -0.9343)
Echo ranges 1018.7898m 1020.697m 0m 1024.7287m
Echo classes 3 3 0 2
Shot discarded.
Depending on the file I am running, it is possible that very many shots are getting discarded due to this which is unfortunate. I got the same warning from files of different ALS-acquisitions from different sources. I tried to find out the reason for this, as I assumed a faulty LAZ-file. The echo that causes the problem is of class 0 (never classified) and its range is 0m. If I understood correctly, this would represent an echo directly at the sensor. In my case it would be directly where the airplane is located at that time.
I looked further into it and wasn’t able to find points of this class 0. Neither LAStools nor CloudCompare identified points of class 0 in these files. There were also no echoes visible that are far from the ground indicating to be close to the airplane altitude. Have you ever encountered something similar, know where this echo could come from or how to fix this? Thank you very much for your help.