Agisoft Metashape

Agisoft Metashape => Camera Calibration => Topic started by: kfish on October 23, 2020, 08:28:39 PM

Title: Camera Alignment from Aerial Survey Producing Significant Elevation Errors
Post by: kfish on October 23, 2020, 08:28:39 PM

Hi All,

I am brand new to Agisoft as I just starting using it to construct orthomosaics and DEMs for my PhD research. I am working with a ~20 km x 8 km area that was surveyed at 15 cm resolution with 60% overlap. I managed to produce the orthomosaic without too much issue but then when I put together the DEM I realized that one region is reading far too high for elevation. When I went back to look at my camera alignment I noticed that many frames were showing elevation errors of up to 100 meters. The errors were so significant that is actual visible in the model of the cameras (see attached screenshot). I have other DEMs of the area and also know that it shouldn't be more than a few meters in elevation yet am getting far higher.

I don't have ground control points, so I am unsure on how to correct the error. I am have tried reprocessing the images and have both processed them as a complete set (all images from the 16 passes) and in small groupings of plane passes. The error is produced in both work flows.

I followed this tutorial to produce the products: https://www.agisoft.com/pdf/PS_1.2%20-Tutorial%20%28BL%29%20-%20Orthophoto,%20DEM%20%28without%20GCPs%29.pdf


Any ideas on how to fix the errors would be greatly appreciated! One thought I had was generating my own set of control points with lat/long/elevation based on the previous DEMs I have, but I am unsure if that would correct the error?

Thanks,
Kfish

Title: Re: Camera Alignment from Aerial Survey Producing Significant Elevation Errors
Post by: Alexey Pasumansky on October 28, 2020, 03:54:00 PM

Hello Kfish,

Can you provide a screenshot of the Tools Menu -> Survey Statistics dialog of the camera errors tab?

Title: Re: Camera Alignment from Aerial Survey Producing Significant Elevation Errors
Post by: kfish on October 28, 2020, 04:39:45 PM

Yes, I've attached the results from the Tools -> Survey Statistics option. Survey_1 and Survey_full show the Camera Overlap results. Survey_1_locations and Survey_full_locations show the results from the Camera Locations results.

If this is not the right thing to be showing, let me know. Still learning where all the options are within Agisoft.

Thanks for any help!

Title: Re: Camera Alignment from Aerial Survey Producing Significant Elevation Errors
Post by: Alexey Pasumansky on November 01, 2020, 11:17:41 PM

Hello Kfish,

Does it help, if you uncheck the cameras with the highest errors in the Reference pane and then press Update button on the pane's toolbar?

It seems strange that there is camera (or cameras) with 15 km altitude error, like if camera has 16000 instead of 1600 m value input for altitude.