Agisoft Metashape
Agisoft Metashape => Bug Reports => Topic started by: Davier on April 26, 2019, 07:13:22 AM
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I have been building orthophotography from historical imagery now for nearly five years and am having a real struggle lately with the accuracy of the exported orthos.
When orthos have been built, I check the location of the control on those orthos prior to export. Once exported, I overlay the control on the orthos again in Global Mapper. I am finding that during the export process, the orthos are shifting meaning that the control does not now fit and the orthos have moved out of position. This is random and not by the same amount each time.
I have built these orthos a number of times to try and get a better result, each time taking nearly three days to process them so I am losing valuable time.
Can you please suggest why there is a shift error.
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Hello Davier,
Are you using scanned images with the fiducial marks?
How many control points are used to the projects typically, what is their distribution across the area of interest and how large is the error that you are observing?
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Davier,
I don't think so that it is any bug but from what I am seeing is that the historical aerial photos does not have their known coordinates in the old days...
What I would do is place each the markers using the x,y,z first and then when you are done with it hit the Update button.
Review them and then do the workflows and export them to orthomosaic and see what was the results
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Hi Alexey,
Yes I am using scanned images with fiducials. No issues there. The project that I am currently working on has 275 frames and I have used 62 control points which are distributed evenly throughout the project area.
As far as errors are concerned, they are random being from less than 1m through to 11m in some areas.
I am currently reprocessing the whole project, putting in a lot more control first to get the setup as tight as possible. Hopefully that will give me a good result but I am not holding out too much hope.
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Hello Davier,
Are all XYZ coordinates for the control points known with high accuracy?
Have you tried to leave some of the markers unchecked to validate the accuracy according to their errors, are you observing large errors for them in such case in the Reference pane?
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Hi Alexey,
The imagery is flown with a wide angle camera (11.5cm lens on a 18 x 18cm format) at 25,000 feet so the raw GSD is about 0.94m. The control is accurate to +/-2m in XY but to about 0.2m in Z.
What is happening is that I am getting a reasonably good set up (Alignment / AT) and even right through the process, getting errors in the +/-4 - 5m range which I am expecting. When I check the orthos in Agisoft after the build, with the control positions overlaid, they are all quite reasonable and expected given the GSD and the control accuracy. When I export the orthos from Agisoft however, the orthos shift their position which I have never seen before. That is my problem!!
The attached files show two different points at opposite ends of the project. The "Agisoft" files show where the control point falls when the control is viewed within Metashape itself. The "Global_Mapper" files are where the exact same control file is viewed over the exported orthos when loaded into Global Mapper. The images have shifted. Why?
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Does anyone have anything further on this? The silence is deafening.
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Does anyone have anything further on this? The silence is deafening.
As i a newbee here, this might not be an answer but have you checked that the export coordinate system is identacal to the one used to generation, that tha datumare the same
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Hello Davier,
Can you share the project file in PSZ format with the alignment results only and placed markers to support@agisoft.com?
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Is there any solution for this problem?
I am also having the same problem. Ortho images in Metashage have good alignments with GCPs, but once I exported to TIF, they shift randomly by half to a meter.
The coordinate system I am working on is NAD83 State Plane for Metashape file and GCPs. The location file of photos is in WGS83.
Export Orthomosaic function in WGS83 and NAD83 State Plane give different results.