I've been searching the forum and read all the manuals avalible for Context Capture Master and the process of aerotriangulation and productions of orthophotos. But I'm still uncertain on how the process should be conducted in order to achive best result in shortest time. There are - in my perspective - too many options and settings to be altered without any proper explanation on how they affect the process and the final result.
So my question is, has anyone developed a standard process that could be described and applicated on a project like mine?
We have houndreds - or even thousands of photos shot with at simple consumer grade drone with a 12Mp camera from 80m height, 70/80% overlap on photos and it should all now bo georeferenced by survey grade control points - GCP:s collected with our GNSS-equipment. Our goal is to produce up to date orthophotos with 2,5 to 5cm resolution per pixel.
All our trial projects, so far, have come out with decent results, but that is after several trials and as it seems they may be successful or not, regardless of some of the settings we try. Unfortunately forrest parts won't be included in the photo process and house roofs come out with rounded corners. I can't get my head around things like the difference between "adjustment constrains" and "final rigid registration" although it is briefly described in the user manual. Also I find it strange when adding control points to the project and they show up all over the model - or atleast several at the time on single photos in the process of pointing out their position.
Any help is appreciated!
Anders Theodorsson, Ludvika Municipal GIS-office
Best practices:
Dear Oto - and "community members"
It's been a while since I posted my question and had Oto's swift reply. I'm sorry to say I'm still struggling to achive an acceptabel result from the aerotriangulations I run and the orthophotos I produce are sometimes really good and next time very poor quality. It seems like a random process and it's really stressful not being able to tell why things turn out like they do.
I still haven't figured out what settings to use in the different steps from first aerotriangulation through a second AT to a production of orthophoto. All instructions and manuals i find are both outdated use small size projects suggesting one should "try what settings are the best for the project". Well, it is not a quick process trying different settings when the AT-process takes 12 hours or more and the orthophoto production takes more than two days to complete!
In my last project with over 7000 photos several hundreds of normal quality nadir photos are not included in the main component. Even though I've pointed out survey grade control points on many of them. Why does this happen? Next photo in the flight line may very well be included but not the one with the GCP on it. I wouldn't be surprised if som photos only showing trees would not be included but in my case there are many with plenty of infrastructure objects that should easily be identified on other photos. Now they are not used in the main component and pointing out "User Tie Points" doesn't seem to help either.
Surely there must be an easy access guideline on how to set up the project starting with nadir drone photos and survey grade GCP:s to complete a good aerotriangulation and then produce both orthophotos, DSM and 3D-mesh - all georeferenced in a local coordinat system? If anyone know where to find that instruction I'm deeply greatful to get some advice on how to find that in the djungle of outdated info out there!
All the best,
Anders Theodorsson said:and had Oto's swift reply
Yes that was what I was afraid that there will be no swift answer from Bentley. You should consider logging SR request or ask money back if no help and software is not working as advertised.
Anders Theodorsson said:but not the one with the GCP on it.
This mostly happens when GCPs are innacurate or doesn't fit correctly. As I said Nadir is not too well suited for 3D mesh.
Hello Oto
Funny enough, just before your post showed up here I had an answer from Bentley support in Canada on my latest SR request! They have som basic suggestions, all of which I've already tried. But the support technician offers to connect over the net for a remote session next week which sounds great to me - applouse!
So I'm waiting for a confirmed booking and hope the net will be fast enough to show what it is all about, cross fingers!
The GCP;s we're using are picked up with a GNSS-device having RTK-correction signal from Swepos giving us single centimeter tolerans. So that shouldn't be the cause to all misshaps. I have noticed the GPS positions stored on the photos from our drone are really bad jumping around several meters. But the photos still show up in reasonably good order after the first AT not assisted by any GCP;s
When entering and setting the GCP;s as adjustment constrains in the second AT I assume those low accuracy positions from the drone would just be ignored. But apparently they are still used to show the quality of each GCP based on how much it alters from the photo position recorded by the drone - which is a bit strange to me.
When it comes to 3D-mesh production I still have a long way to go since we first have to make good orthophotos and DSM;s for whole town before we even try next step. Looking forward to that!
Did you ever get this issue resolved? In the future, to check that the photos go together, you might try doing a quick AT with a heavy downsampling applied. At least if it doesn't go together you haven't wasted 12 hours.