vertical bended alignmend of drone gps scan and pictures from a flat road

Development Asset Creation
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1

Hello everybody, 

I have a misalignment of a road scan made with a dji Phantom 3 Standard and  litchi, n the latest Version of Reality Capture 1.0.3.3939.

A flat road was bended vertical.  

It was taken by a pre-planned way point flight mission in constant altitude of 15.00 m. The flight was fine and the drone was stable, precise and smooth at the preassigned altitude.

I used this drone for many scans in the past with earlier versions of RC without any problems.

I´ve checked and tested differed GPS relevant  alignment- and import settings in RC for this scan but without any success.

The road is banded.

Any ideas  to fix it?

Best regards, 

Uwe

 

 

2

Hello Uwe,

I believe it is caused by the error cummulation due to shooting in one direction (along line).

You can find some tips how to avoid this effect for example here:

https://support.capturingreality.com/hc/en-us/community/posts/115001359872-Camber-in-CR-reconstructions

https://support.capturingreality.com/hc/en-us/community/posts/115002474112-importing-camera-calibration-bowl-banana-shape-effect-

3

Hello Zuzana, 

thank you for your support and the links.

It was helpful.

I changed the distortion model to „Brown4 with tangential2“.

 

Another point was, to switch the RC project coordinate system and output system to GPS WGS 84.

 

At last I set the „Prior calibration“ to „Fixed“ and the „Prior lens distortion“ to „No lens distortion“.

(I already dewarp the images in adobe bridge with the lens settings for the dji P3S lens.)

 

Here some screenshots:

 

Thank you and best regards, 

Uwe

 

 

 

 

 

4

You will get better results with no prior un-distortion - one of the basic rules of photogrammetry…  :slight_smile:

5

Hello Götz, 

thank you for your response, but I can´t confirm.

I do several hundreds of scans with DSLR cameras, drones, LiDar and professional Scan rigs with ca. 120 cameras. 

After using RC for more then two years, my experience is, that it depends from case to case.

Sometimes undistorted pictures work better, sometimes not, -there is no basic rule in practice.

I use Canon cameras with the „Canon Digital Photo Professional“ tool for developing the raw images with the lens specific correction etc.

It will improve the images regarding sharpens, distortion, chromatic aberration … and the final RC 3D Model a lot.

I have made many high end side by side tests for different cases and objects. 

In this specific case, of course I tried the distorted pictures too, but the result with undistorted images is much more accurate.

Best regards, 

Uwe

 

6

Hi Uwe,

sorry, but it wasn’t entirely clear from your post that you know exactly what you’re doing! In most cases undistortion by beginners is a big source for errors.

I agree generally with your statement that it all depends on the circumstances. I myself had a case where I couldn’t get a model to align properly and my solution was to use a competitor and export the undistorted images from there, fed them into RC and it worked. Buta big part of this issue is what you consider as “better”. I am genuinely interested: which aspects improve over uncorrected images in your case? Alignment, noise in the mesh, texture?