I'm having issues with DJI Terra freezing during 2D reconstruction, gets to about 50% and freezes, left overnight and inexactly the same place the next day.  Deleted the mission, and started again, and same issue.

Running the latest version 3.6.0
Using DJI Mavic 3 Enterprise RTK drone
Importing 3320 photos with 8 GCPs, and 8 check points
Using an arbitrary co-ordinate system - site is closly related to OSGB, but on a slight shift with a scale factor of 1, so OSGB co-ordinate system isn't working.

This is the 2nd time i've done the same flight, no issues first time, only dfference this time is i've added in more GCPs and check points.  New to using drones and DJI software and wantedto see the impact of more/less GCPs on the residuals.

Any advice?

Sounds like computer hardware issue. 3320 photos, is there enough memory ?
Anyway DJI Terra is not a good value for professional.

arbitrary coordinates ! why not WGS UTM ?

Running an Intel i9 with 64GB RAM, 2TB didicated Solid State Hard drive, plenty of memory.

I'm new to drones and this was recommended software from Coptrz, whats the alternative?

Would WGS be a better alternative?

Once you start building on a site, you need a scale factor of 1, OSGB etc all havea scale factor slightly less than that to allow for the curvature of the earth.  Esentially you are using a local grid.

Trimble GPS you create a site calibration to allow for this.  Leica you create a co-ordinate system to allow for this.  How do you allow for this with DJI software? Arbitrary co-ordinates allows the software to shift to a local grid and scale factor?

FT Site Eng Posted at 12-3 09:10
Running an Intel i9 with 64GB RAM, 2TB didicated Solid State Hard drive, plenty of memory.

I'm new to drones and this was recommended software from Coptrz, whats the alternative?

Coptrz is a DJI seller, and as a good seller, he recommends the DJI product to the customer, even if the product does not meet your needs.

Since you seem to have Trimble equipment, I describe how I proceed:
-GCP acquired with Trimble+ site calibration
-Agisoft Metashape, coordinate system that adapts to your needs, aligns with GCP as described in the manual

And you will have 3D and 2D map ready.

WGS UTM is a good alternative yes, remember this is a small 20MP sensor on the M3E, quality may change depending on light/weather conditions. It's a bit overestimated to expect to have more than +/-5cm of precision.

My feeling is that you are an experienced surveyor, who wishes to improve the quality of his work thanks to new technologies, Am I right?

Unfortunately, photogrammetry and DJI products in general are not designed for high quality investigation. If you need very accurate results, your best option is still LiDAR, not DJI but RR, Yellowscan... That's a problem with DJI dealers, they don't know much and don't take the time to listen your request and to offer you the best equipment. The main goal for most of them is to squeeze the most money out of your budget.

I think you already know it but I remind you anyway, DJI sensors only give ellipsoidal altitudes. A reference geoid is needed to correct this. Metashape handles geoid .tiff .gri .ggf very well (Trimble) This is not the case with Terra.

I have no commercial link with the brands mentioned above, I simply share the brands that give me satisfaction.

I just check, OSGB36 have a scale factor of 0.9996012717
Honestly, if you prepare a dataset with OSGB36 and another with an arbitrary system that has a scale factor of 1, the difference will be so small that it will be few ppm, and anyway be below the range of precision that the photogrammetry.

I don't know the nature of your project, maybe you can tell us more...

Thanks for your help LV_Forestry.

You are right about wanting to explore new technologies.

I have flown the same flight on this site (exactly the same flight), and run it through DJI Terra with no issues.

I understand different technologies and the acheivable results, ie +/- 25mm on GPS observations.  I'm getting within +/-10mm on 2D ad 3D on my GCPs and within +/- 50mm on my check points. I now need to play around with the quantity / positioning of these to see what effect it has on the accuracies of my surveys.

I have another site on the go that was set upon OSGB, and setting this to the co-ordinate system gives me great residuals.

On the site with the 'local grid' the existing stations were 150-200mm off from OSGB.  When trying to tie the flight in with an OSGB co-ordinate system i was getting about 150mm errors to GCPs and check points.  Changed to an arbitrary  co-ordinate system, and was getting sensible errors of about 30mm.

The difference between OSGB and a scale factor of 1.000 are approx 10mm / 100m linear distance, which over a site that is 400-500m, makes a bit of a difference.

Unfortunatly i have bought licence for DJI Terra already, so am just trying tofind a solution that works, and hopefully doesn't make the software freeze halfway though the reconstruction

FT Site Eng Posted at 12-3 10:51
Thanks for your help LV_Forestry.

You are right about wanting to explore new technologies.

You're welcome

I mainly do forest and agricultural field surveys, not needing high precision for these applications I am satisfied with the DJI sensors.

The distance gaps between OSGB and arbitrary coordinates are huge. I have this kind of discrepancy when I try to place geoidal height GCPs with ellipsoidal height images.

You can download the demo version (which is complete) of Metashape. If you don't want to bother with that you can send me a dataset, I can pass it in Metashape and send you the rasters. I will be surprised to find a gap of 10mm every 100m with this software. You can use Google Drive

So DJI support have accepted that it was freezing, and it was freezing during reconstruction when a 'field' secene was selected, reconstructing the model as 'urban' solved the problem.

3D reconstruction froze when 'refine water surface' was checked, and worked fine without.

They are still scratching their heads as to why this is happening.

I'll keep this thread updated incase anyone else is suffering the same issues

Thank you for this update.
Was it DJI who answered or a local DJI dealer?

DJI themselves, local dealers generally don't have a cue about the ins and outs of software

What DJI are saying, is that becasue teh project is a mix of grass, and bare earth, i should be using 'urban' scene when carrying out a reconstruction

"based on the complete reconstruction results you provided, we can see a large area of non-grass/non-Field scene. It's recommended to give priority to the Urban scene as we suspect the DJI Terra calculations are having anomalies when switching to the Field scene, leading to the progress remaining stuck and unchanged."

I am dealing with this same issue right now.  Urban scene runs fine, however you cannot access agriculture mode when you do an urban reconstruction.  I am building maps and sending them up to the Agras cloud, so Urban scene is not an acceptable solution.  I am running 2 other machines with the same version of Terra on them with zero issues.  This is only present on my new laptop, which is a MSI Titan GT77 HX… should NOT be a hardware issue!

I left TERRA a long time ago for the same reasons.  And obviously nothing has changed.