Hello,

I'm having some trouble with the initial setup/calibration of the Zenmuse L2,
I've followed the instructions as per the DJI video tutorial (DJI Zenmuse L2 Lidar Self-calibration (youtube.com)),
I've completed the calibration flight, uploaded data to Terra and processed it as a LiDAR Calibration mission.

Issue I'm having is that a .tar file is not generated in the terra_lidar_cali folder,
instead within this folder there is a .zip folder containing two files; sfm_report.json and user_extri.cali.
Have tried uploading these back onto the SD card and plugging into the L2 unit to see if these calibrate but they don't,
when I take the SD card back out and check the extri_update.log files, the log is blank with no successful message.

Can anybody suggest where I'm going wrong?

thankyou in advance!

Hi there, thank you for reaching out. For your inquiry, would you please take a screenshot of the task parameter settings in Terra.We will forward and help you to further check with our engineer team. Thanks.

Why do you want to calibrate the L2? Is it a brand new unit? Did you encounter major deviation?

Hi there, after checking with engineers, we may need to collect some information with you for better checking. Could you please provide a screenshot of the task parameter settings in Terra? Thanks.

AR_AirPrecision Posted at 4-20 05:39
Why do you want to calibrate the L2? Is it a brand new unit? Did you encounter major deviation?

Yes it's a brand new unit,
tbh have just assumed it needs an initial calibration similar to the P1...
Am I wrong for assuming this and the unit is good to go out of the box?

thanks

DJI Thor Posted at 4-21 22:51
Hi there, after checking with engineers, we may need to collect some information with you for better checking. Could you please provide a screenshot of the task parameter settings in Terra? Thanks.

Hi,

Please see attached picture,
is that what you require?

Many thanks

CWIC Posted at 4-22 01:44
Hi,

Please see attached picture,

Thank you for your reply. Here is the screenshot for your reference. Please ensure to the LiDAR calibration is chosen, and the reconstruction is completed.

DJI Thor Posted at 4-22 02:18
Thank you for your reply. Here is the screenshot for your reference. Please ensure to the LiDAR calibration is chosen, and the reconstruction is completed.
[view_image]

Hi Thor,

Yes I did ensure that the LiDAR Calibration scenario was selected,
have tries processing it several times but still no .tar file is generated....

CWIC Posted at 4-22 00:27
Yes it's a brand new unit,
tbh have just assumed it needs an initial calibration similar to the P1...
Am I wrong for assuming this and the unit is good to go out of the box?

I didn't do any calibration, did you fly and check the results you get are acceptable for your business case?

CWIC Posted at 4-22 03:45
Hi Thor,

Yes I did ensure that the LiDAR Calibration scenario was selected,

Just to confirm, did you click on the 'export calibration file' button? (Pic 1)

Also, may I double-check if the folder you checked was 'lidars/terra_lidar_cali' (Pic 2)? If it wasn't, please check if there is a .tar compressed file in that folder. Please keep us updated on the status. Thank you.

DJI Thor Posted at 4-22 05:54
Just to confirm, did you click on the 'export calibration file' button? (Pic 1)

Also, may I double-check if the folder you checked was 'lidars/terra_lidar_cali' (Pic 2)? If it wasn't, please check if there is a .tar compressed file in that folder. Please keep us updated on the status. Thank you.

Hi Thor,

Yes I did click 'export calibration file', I am then  presented with a compressed file which when unzipped just contains the same files as shown below (the same files which have been generated and stored in the 'terra_lidar_cali' folder within the project folders).





thanks,

CWIC Posted at 4-22 08:41
Hi Thor,

Yes I did click 'export calibration file', I am then  presented with a compressed file which when unzipped just contains the same files as shown below (the same files which have been generated and stored in the 'terra_lidar_cali' folder within the project folders).

The file to put on the SD card is the one you unzipped.  Leave it in compressed format and copy it to the root of the SD card.  

Then you put the SD card in the Lidar that you put on the drone.  You turn on the drone, and the procedure will start automatically.  It lasts 5-10 minutes.

As AR wrote, it's pretty useless with a new unit, it's not even recommended to do it unless you find a significant gap between the point cloud and its colorization.  

I have never succeeded in increasing the quality of the point clouds by doing the calibration.  This procedure only seems to be useful for aligning the images and the cloud in order to assign the correct color to the points.

I see you are in the construction industry.  I don't know if this is your first LiDAR experience with DJI, but be careful.  

The ratio quality / money is very good, however if its so cheap vs other brands on the market, it is for a good reason.

You have to be wary of the features of the paid version of Terra such as the smooth point cloud, takes a lot of liberty with reality.  Otherwise the LiDAR itself is good, although on certain structures there are strange things that can appear on the point cloud.

CWIC Posted at 4-22 08:41
Hi Thor,

Yes I did click 'export calibration file', I am then  presented with a compressed file which when unzipped just contains the same files as shown below (the same files which have been generated and stored in the 'terra_lidar_cali' folder within the project folders).

Hi CWIC, thank you for your reply. Based on the picture, this is the tar. file (It just does not show the suffix).



To ensure proper installation, please copy the tar. compressed package directly to the SD card of L2 without decompressing it. After copying, please install L2 and turn on the aircraft. Wait for a while to see if it works properly.

DJI Thor Posted at 4-24 00:24
Hi CWIC, thank you for your reply. Based on the picture, this is the tar. file (It just does not show the suffix).

[view_image]

I see, thankyou for clarifying that!

LV_Forestry Posted at 4-22 09:20
I see you are in the construction industry.  I don't know if this is your first LiDAR experience with DJI, but be careful.  

The ratio quality / money is very good, however if its so cheap vs other brands on the market, it is for a good reason.

Thank LV, appreciate you input!

I am definitely wary of using the smoothing feature, particularly where accuracy is important!
Any recommendations on overlap parameters?
Will principally be using the L2 in repetitive mode for mapping

CWIC Posted at 4-24 07:31
Thank LV, appreciate you input!

I am definitely wary of using the smoothing feature, particularly where accuracy is important!

You need to find the settings that suit you best. Its hard to recommand THE settings.
For a Lidar
-the overlap depends on the altitude and the height of the structures.
-point density is a function of altitude and speed.
In the center the precision of the points is good. The more angle the laser takes, the more likely there will be deformations.

As a general rule I put at least 50% and I aim for at least 200pts/m2, no more than 50m from the target surface.

CWIC Posted at 4-24 07:26
I see, thankyou for clarifying that!

Our pleasure to help. Please try and keep us updates if you need further assistance.