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Check points not within 2-3 times GSD

Hi All,

 

I have completed a project (ignore the ortho mosaic in the quality report, I cleaned that up with a processing area) and I am concerned about the error shown on some of the check points that I have. They are “005” and “014” “6” and “7” as can be seen in screen shot they are a bit off, not major but I would like to get them closer than they are. Any ideas?

 

Is it a weighting problem?

Quality report can be found here:

https://electricitysupplyboard-my.sharepoint.com/personal/colin_donnelly_esbi_ie/Documents/Grouse%20Lodge%202_report.pdf?csf=1&e=c818a559489648699eb22b6b7ce3ef3c

 

Thanks

Can’t get to your Quality Report but the Projection Error per pixel isn’t big at all so if you have accuracy issues then the overlap in taking the pictures is likely the culprit…or some Pix4D settings.

Personally that map view looks like very low overlap but it depends on the camera optics and flight height.  Please provide a public link to your Quality Report so we can provide better help for you.

1 Like

Hey Colin,

Indeed, as mentioned by @Adam, we could provide better assistance if you granted public access to your quality report. 

In the meantime: on one hand, the Error[s] XY, and Z for the check points seem to have higher values than expected, especially since they are higher than 2-3*GSD (as mentioned in the post title). On the other hand, the overall projection error values for all 3D tie points (ground control points GCP and check points) are pretty low. This means the 3D tie points were well marked in the images and that the project was well fitted to the ground control points. 
Note for check point 012: you could check out how you marked it on the images.

There could be a number of reasons why the error values for check points is higher than expected, such as:

  • the location of the check points in the project. The error can be higher if the check points are located on the edge of the project

  • the location of the check points with respect to the ground control points. The further the check points are from ground control points, the lower the absolute accuracy of the position of the check points in the project.

  • the flight plan: mainly flight height and overlap

  • the camera optimization

However, it is hard for us to give you a more accurate response without the quality report. Could you also give us more information about your flight plan?

Additionally, what you should also keep in mind, is that the 3D tie points (ground control/check points) are weighted differently according to the accuracy you indicated. As a consequence, make sure you neither overestimate nor underestimate the accuracy of your ground control/check points.

 

Looking forward to hearing from you!