Hi all!

I have lidar data gaps in some lidar data collected by Zenmuse L1. This has happened in 3 consecutive missions.  Attached is a snip of the gap.


Any idea what could be the problem?

Hi, same situation for me when i lost the RC link.

Hi there, you can check the following possible causes:
1. During the flight, the RTK signal may be lost in some areas which would make it fail to parse the data.
2. Another possible reason is that the IMU calibration was not performed in time, resulting in the accuracy of some areas not meeting the parsing conditions
3. You can provide us with the original data for further analysis.

DJI Mindy Posted at 9-1 22:47
Hi there, you can check the following possible causes:
1. During the flight, the RTK signal may be lost in some areas which would make it fail to parse the data.
2. Another possible reason is that the IMU calibration was not performed in time, resulting in the accuracy of some areas not meeting the parsing conditions

How to share?

GEOID Posted at 9-3 00:38
How to share?

google drive

GEOID Posted at 9-3 00:38
How to share?

You can upload it to Dropbox or Google Drive and then send us the download link here.

DJI Mindy Posted at 9-5 05:34
You can upload it to Dropbox or Google Drive and then send us the download link here.

https://drive.google.com/file/d/1mfxiaNvDdq_Z4Akl8Cl77ty6xN3zBYX6/view?usp=sharing

GEOID Posted at 9-6 09:27
https://drive.google.com/file/d/1mfxiaNvDdq_Z4Akl8Cl77ty6xN3zBYX6/view?usp=sharing

The LAS file is +/- useless. it would be much more interesting to see your Files straight from the L1. Before import them in Terra. Most probably it is a RTK signal failure. The only solution is to use PPK. Then if PPK fullfil the gap, you can be sure this is the problem.
Discussion about PPK :
DJI Terra importing problems | DJI FORUM

Hi,
you interfered exactly the same issue as I had in the April-May of this year. I also wrote about it here back then. You can find my posts on forum.

Unfortunately, it is, probably, DJITerra problem - as it is a black box software, it could simply discard some data due to...GNSS or IMU bad quality data. Normally, user can process such data PRIOR TO and SEPARETELY FROM laser point cloud reconstruction, but DJI doesn't provide such an option.

The only possible solution - use PPK and pray. Or use RTK, but pray much harder then, cause every signal loss will correspond in unexpected loss of the data, which are RECORDED (visible on the LiDAR view on the controller).  

I had same issue due to rtk data transfer interruption during mission (bad 4g coverage in the area). Using PPK with rinex solved the problem.

Hi Guys
I am having a very similar issue. We mostly fly with RTK off, due to there being very little reception where we work and then process with PPK and a Rinex file. However, in the last 4 months every single flight we do has a gap at the start and the end of each flight. if we fly say 500 acres and there are 2 battery changes during this flight. there will be 3 folders created for this flight. when we process this data we get a gap at the start and the end of each folder of data. This is consistent across 30-40 separate missions using both RTK and PPK.
If anyone knows how to solve this. Id really appreciate the help.

AgriNex Posted at 1-1 18:26
Hi Guys
I am having a very similar issue. We mostly fly with RTK off, due to there being very little reception where we work and then process with PPK and a Rinex file. However, in the last 4 months every single flight we do has a gap at the start and the end of each flight. if we fly say 500 acres and there are 2 battery changes during this flight. there will be 3 folders created for this flight. when we process this data we get a gap at the start and the end of each folder of data. This is consistent across 30-40 separate missions using both RTK and PPK.
If anyone knows how to solve this. Id really appreciate the help.

Issue with the SD card?

AR_AirPrecision Posted at 1-2 00:26
Issue with the SD card?

It's across multiple SD cards.

The drone came with a rectangle sheet that has spots on it. I'm assuming that this is some sort of calibration tool. what does this do and could there be any correlation between the fact that I've not used it and the issue I am having?

AgriNex Posted at 1-3 22:43
The drone came with a rectangle sheet that has spots on it. I'm assuming that this is some sort of calibration tool. what does this do and could there be any correlation between the fact that I've not used it and the issue I am having?

Not at all. This tool is made to calibrate the surrounding camera to detect potentiel colision.

Your outcome is definitely tied to how you use your lidar, or your NTRIP network, or both.

Can it be the network though?  given that it happens when we have rtk enabled and when we have rtk disabled and process the collected data with a downloaded rinex. We have also sent our data to UPG to have  them process it and it still came back with gaps at the start and end of every dataset. We have been flying for just over a year with this specific drone and sensor. Our pre flight and flight procedure has not changed in this time. This issue has only been occurring for the last maybe two months.  

AgriNex Posted at 1-3 23:43
Can it be the network though?  given that it happens when we have rtk enabled and when we have rtk disabled and process the collected data with a downloaded rinex. We have also sent our data to UPG to have  them process it and it still came back with gaps at the start and end of every dataset. We have been flying for just over a year with this specific drone and sensor. Our pre flight and flight procedure has not changed in this time. This issue has only been occurring for the last maybe two months.

What is the distance from base station?

The distance to the base varies from a few hundred meters to 8-10 kilometers. Thing is. there are properties that we have flown that have processed perfectly. we have since been back to the same property and repeated that exact same mission to use for comparative surveys and they have large gaps in the data. I also feel that if it was a network issue the gaps wouldn't be so consistent. It is always the exact same amount of data missing from the start and end of every data set.