Exception: Child returned 1 - Lots of trees n min-num features were at 30000


Hi there,

First time posting here, have been browsing around for a few weeks now and have been playing around with WebODM for a few weeks as well. Decided it was time I introduced myself and submitted my first topic.

I work for a company that is starting a division for drones and we’ve started using aerial imagery from UAV to help us with our work. The ODM platform has been showing quite impressive results and I would love to continue learning how to fully use the platform.

So here are the details of one of my issues I’ve had so far. It’s imagery from a patch of forest we were taking pictures for to do some photogrammetry.

How did you install WebODM? (Docker, natively, …)?

Natively on Ubuntu running on a closed server with 16go RAM allocated space and 100Go hard disk drive space

What’s your browser and operating system?

Firefox 62 on Windows 10

What is the problem?

The process fails at the end giving me this message: Exception: Child returned 1

Also under the task box there is this message : “Process exited with code 1” means that part of the processing failed. Try tweaking the [Task Options](javascript:void(0):wink: as follows:

  • Increase the min-num-features option, especially if your images have lots of vegetation

There is indeed lots of trees in this series of pictures, so I have tried increasing the min-num to 30 000 but still didn’t work

What should be the expected behavior?

A good looking orthoimage result

How can we reproduce this? (What steps did you do to trigger the problem? What parameters are you using for processing? If possible please include a copy of your dataset uploaded on Google Drive or Dropbox. Be detailed)

Here’s the drop box of my pictures : https://www.dropbox.com/sh/tkrh031qoam95vd/AABVrQcWArSvi5ItLwyYYsO0a?dl=0

And here is the task output : https://www.dropbox.com/s/o780oxcnhft6uf8/task_output.txt?dl=0

I need to run into a meeting but I will be coming back to see what you guys think.

Also, is there a guide somewhere that explains all the different features in the options menu? I’ve seen mods telling people to try different options but I haven’t found anywhere that explains what they mean…

Like I said, i’m fairly new at this.

Thank you


Hi @kingabelicio, welcome :hand:

Are you running the latest version of WebODM? If you haven’t updated in a while (like, more than a month), try to:

./webodm.sh update

And then reprocess the dataset to see if it fixes the problem.


Did the update and reprocessed the same data set with default settings and then with min-num feature at 50000. Still same error message…

Thank you for the reply,



What kind of overlap and sidelap did you fly with?


Looking back at my flight reports I believe I did 70 Forward Overlap 60 Sidelap


This error: Traceback (most recent call last): File "/code/run.py", line 47, in <module> plasm.execute(niter=1) File "/code/scripts/odm_dem.py", line 112, in process max_workers=args.max_concurrency is different from the previous one.

You most likely ran out of memory here. Try decreasing max-concurrency to 1 or 2.