Topics

1

General / Detect edge of "good quality" pts from drone flight pt cloud?

« on: July 22, 2023, 01:43:58 AM »

Hi there,
We fly many drone flights and compile, and there is always a warped zone around the edges where photo overlap degrades and so on.
I have run the survey statistics report tool and see some interesting things from it, but can I select pts using that?
The question posed to me was "can metashape automatically crop the pt cloud and ortho to some quality boundary?"
Of course, like HHGTTG, what does that question really mean?
I don't know, it was just asked by this guy, you know...lol (book reference)
All out of humor, send any good ideas my way if you got em.

2

General / How are GCP's "weighted" when also using ppk camera positions?

« on: June 06, 2023, 07:56:02 PM »

Hello,
We have a DJI Mavic 3E, and use a ppk workflow. Surveyors run a base station but we don't hook to it (no RTK).
We process our photo locations through TBC and get a text file with adjusted camera locations for metashape.
We use that text file as reference and works well.
TBC has an issue where the elevations are lifted up for some reason by 3 or 4 ft.
We typically set 4 GCP's which we have correct coords for (no error like ppk data...), and when we add those in, the elevations are corrected.
Why is that though? We have 300 cameras and only 4 gcps.

The question is how the GCP's modify the results, compared to just camera locations used.

This is quite important to know, but also likely has a few answers.
Is there anything "clear" than can be said about adding gcp's, like "they dominate the vertical placement of the results"?
This topic is super important to understand when discussing why gcp's are still recommended in ppk workflows.
In our case, our ppk elevation values have issues which we will fix eventually.

thanks,

3

General / The Meaning of GCP's moving from coords after processing pt cloud?

« on: October 02, 2020, 06:20:57 PM »

I've been using metashape for a few years now (was PS), and ran into somthing I need to understand.
I'm a civil that flies a phantom 4 pro, and has GCP points on the ground.
I use the USGS workflow I have posted here before, and generally get super good clean results.
I had a run though, where after processing the control points show quite a bit above the ground.
It occurred to me to uncheck the markers and I realized there is a "real" location, and "compiled" one - wow.
If I uncheck the markers, they show at coords I gave them and are right on the ground.
Now I am wondering what to think of this. Why would the results be essentially correct, yet the markers moved vertically after processing?
I know unchecking makes them check points. Does a large difference (more than 1 foot) between original and final location indicate anything is bad?

I'm literally facing my boss and client, wondering if I should use the data or discard and refly.
thanks

4

General / Markers not refining location after I move a few to get green flags

« on: March 25, 2020, 02:39:46 AM »

I have used PS, now metashape, for a few years and same drone (P4P V2), and always follow the same workflow.
I use the USGS workflow so am doing things super common to most.
Lately, maybe in last 2 months, when I pull in text file with ground control points, the markers come in fine.
Then I go through my regular steps of:
1) right click in model by a marker, then "filter photos by point". that works.
2) place or drag the markers in a couple photos to refine the location, turns them to green flags.
3) NORMALLY - that causes the same marker in other photos to move very close to those first two.

Now, the markers are not adjusting, and I have to move them a large amount in the remaining photos.
Many times I have to hand place them, they don't even show.

This is much slower than before, as I can't even use the "filter photos by markers" once I adjust a couple, as that is better than filter by point.
I have been trying to keep up with latest version but not sure when exactly this started happening.
I have no issues otherwise. GPS data on photos is fine, aligning cameras is fine...its all good.

What settings could affect the other markers to keep them from self adjusting closer to the first couple I hand adjust?
thanks

5

General / Creating orthomosaic seems to take way longer with metashape

« on: April 11, 2019, 06:35:39 PM »

I just installed metashape which replaces photoscan, of course, and the ortho creation step is way slower now.
It used to take an hour for about 400 photos, now its taking 2 hours.
This is a critical issue I cannot just ignore.
I need some feedback on this or have to go back to photoscan.
thanks

6

General / Shouldn't the dense pt cloud exactly match GCP's at the GCP locations?

« on: April 10, 2019, 01:07:02 AM »

I've been using PS Pro for about a year now, and have generally gotten really good results using both "targeted" GCP's, and points I "photo ID'd" after the flight and got coords from previous survey. I fly a DJI P4 Pro V2, very typical setup.
Today, I flew a job and generated GCP's as normal, such that they are 2x flight height apart. I flew at 250', and have GCP's 500' apart.
My workflow is that of the USGS, as written about in these forums.
I align photos, convert to CA83-VIF, eliminate low quality pairs...all that, and then uncheck the images.
I bring in control coords, tell the photos where the GCP's are, and eventually build dense point cloud.
My question is:
Once I get the dense point cloud, should the points right at the GCP's exctly match the elevations of the GCP's.
I thought in the past they had. Today I got points as much as 1.2 feet off. Then some dead on.
I know PS involves a lot of factors, but assume I have very good imagery, good overlap, and so on.
I'm trying to figure out proper PS behavior so I can troubleshoot problems with me, or it.
thanks