Hi all,
since I am doing photomapping of terrain,
I have experienced, that the light tends to change progressively as I shot photos.
The problem is, the flight is following zig-zag or spiral shape and as a result I have gradual variation
of brightness and contrast across ortophotomap.
In my case I am striving for fast response, not for HDR quality, and it might be difficult to repeat a mission
that takes up to 2h of UAV flight.
The question is, are there any tools that can linearly/gradually or maybe automatically apply some correction to a list of images?
We are talking abotu 300-3000 photos per flight, up to a few times per day. A real mill.
I am aware of ImageMagick toolset, but it is not a solution:
The problem is that any automatic method I know gathers statistics over a single image, then applies the correction to one or many.
Also ImageMagick scripts I tried to apply by merging photos etc show insufficient processing speed of Image Magick (it is general tool, with dozens of intermediary memory copies/logic layers during processing a script).
What is needed is a tool that analyses 3..tens..all neighboring images (consecutive in the list) and applies slowly changing correction.
I know that somebody will advise fixing exposition in the camera but thsi is NOT the way to go in 50% cloud cover changing the lighting 8 times during the flight.

What is needed is something like Deflicker algorithm used in movies, but this would be ideal but I doubt it exist for photos.
At the moment I am looking for anything that works.

I know the issue could be known to ppl doing Timelapses but I have no idea what are the solutions (I guess they usually merge the results into a movie, then apply Deflicker filter in movie processing soft, but the resolution, compression and quality is lost).

At the moment typical application of autobalance or histogram equalize/anything leads to photos where 1 out of 20 pops up with very off colors or other parameters.
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  • T3

    Not of this speed. Enso does processing of quantities as fast (or slow) as for small quantities. it has structured approach that finds the neighbors using GPS what puts him already above all others stitchers that ignore GPS.

  • Ok Krzystof, this is market prices, that's true, and no surprise. But for this amount, you don't have access to a correct blend soft ??!!
  • T3

    @Stephane, for me, if looks like something between 5KEUR and 18KUER but it depends who, what, how.

    This is why I told you to ask Ismo. It is not a secret, just such prices are not published wide open because there is always somebody that will pop up saying: hey look I got the same from ptgui for 300USD what is nonsense but they would spend their life explaining basic things to everybody.

  • In fact Krzysztof it's not exact, there is in the Panotools suite an utility that can manage with camera translations.

    Pstereo I believe. Tested it : peace of sh..t, but anyway : it does exist !

    You should really have a (deep) look at Panotools...

  • T3

    There are 2 problems:

    1. if you prerotate, you lose a lot of overlap or have lot of balck surface

    2. was llooking aroudn ptgui but there is a basic issue: it is NOT designed for camera moving above the model,

    this is for a model surrounding the camera. there is no position input. even if you pre-rotate, teh result is passed through dozens of projections.


    Also Palentier Stitcher has shown already that simple projection methods are not precise enough.

    Not a surprise, even military cannot locate target with more than 10 m precision from a small UAV.

  • Your true, for extrinsic matrix, APM is not good enough, but John was talking about a process with accessible tools like hugin Ptgui... For a quick mapping of a flat surface with a few pictures, I believe you can achieve good results, and show it proudly to your friend in your livingroom, and that's perfect as this !

    Well about my soft, now... Absolutely no need of extrinsic matrix : based on SIFT like your true.

    Terrain extraction is based on a photogrammetric approach, so results are directly ok for orthorectification of pictures. Residues are good, but actually I have tested it (on approx 200 pictures sets) taken from my paraglider with 23mm focal Kodak compact horrible quality (!), and yes it works very well, even with a lot relief.


    Everything absolutely automatic, of course, just have to worry about your electrical bill ! But I didn't go further at the moment, and everything is in an horrible command line form...

    Are you looking for a software, or a subcontractor ?

  • And for orthorectification terrain (DEM) is necessary. I'm afraid that APM data are not precise enough for this task. I'm working with optical IMU with geodetic grade L1/ L2 GPS reciver and GPS measurments are post processed with GPS base station and correlated with IMU data (Kalman filter) and with this kind of data I still have to perform image tie point search to achieve perfect result. There is usually some small image misaligment (0-4 pixels). All this on terrain surface that is result of LIDAR scanning.

    I don't know but I presume that APM data are maybe good enough for a basic exterior orientation of images to enable faster tie point search. My opinion is that for absolute orientation of images IMUs with more than 1°/h drift and less than 200Hz sampling rate are no go.

    Rocca I would like to ask you to describe your software a little bit. Does your solution operate with unoriented image set using some sort of SIFT approach or does require roughly oriented images? What about terrain extraction? I'm really curious because I'm looking for small budget solution (not several 1k€) to produce orthos from UAV.

  • You mean a special optimization : only rotation on the pictures already GPS placed on a map ? You could use APM output to set orientation too.

    Well it's a good idea, but you still have a problem because GCPs can't be optimized. Panotools can only optimize pictures taken from the same coordinate, with only rotations, no translations for your camera.

    Need orthorectify first !

  • Developer
    hmm.. Just thinking out loud here now. You could try placed the photos at the correct GPS position (using a script to generate a project file) when loading them into Hugin/PTGui, and then do alignment/blending calculations with X/Y movement of the images disabled.
  • Don't mind... It's more than several thousands, I'm quite sure !

    My own soft do everything of that anyway, based on opensource ;)

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