Forum

Author Topic: fog on orthophoto  (Read 9882 times)

lins

  • Newbie
  • *
  • Posts: 13
    • View Profile
fog on orthophoto
« on: January 10, 2013, 06:19:39 PM »
Hello,

I need help, I have fog on my orthophotos of megaliths and I don't know why...
Is it a bad alignement of the photos? Or during my capturing session I have done bad pictures? My orthophotos parameters are wrongs?

I had a precedent model with less photos and that worked as I want (picture top right) but my model wasn't complete. So I have taken more pictures, now I have a complete model but I have this problem.

I have to do a presentation with these orthophotos during this week-end so it's really urgent...

Sorry for the poor quality of my attach document.

Thanks to you

RalfH

  • Sr. Member
  • ****
  • Posts: 344
    • View Profile
Re: fog on orthophoto
« Reply #1 on: January 10, 2013, 06:31:52 PM »
One thing you can try is to look at all the photos in your project and disable those which are too bright or not sharp before generating the orthophoto texture. In many cases, for texture you don't need all the images that you needed for geometry reconstruction.

Going back to the same site to capture more pictures on another day is always tricky, because lighting conditions change (e.g. diffuse vs. direct light, different illumination angle...). In cases where you later realise that you don't have enough pictures for a model, it's usually better to take a complete new set of photos. If you have done that, perhaps disabeling the "old" photos in your project would help.
« Last Edit: January 10, 2013, 06:33:23 PM by RalfH »

Alexey Pasumansky

  • Agisoft Technical Support
  • Hero Member
  • *****
  • Posts: 13913
    • View Profile
Re: fog on orthophoto
« Reply #2 on: January 10, 2013, 06:35:00 PM »
Hello lins,

We could advice you to check if the original images are not blurred (otherwise, please disable such images before exporting orthophoto), and try to use Mosaic blending mode.

If it doesn't help, please let me know. Maybe it will be possible to provide us the project file with original image set?

Best regards,
Alexey Pasumansky,
Agisoft LLC

lins

  • Newbie
  • *
  • Posts: 13
    • View Profile
Re: fog on orthophoto
« Reply #3 on: January 10, 2013, 07:09:33 PM »
Thanks Alexey and RalfH,

Fo my second set, the pictures are from one set but my subject is like a cave context without light. I used white light, to do my photos, but the lighting isn't steady.
So I disabled 4-5 blurred or bright images and I try Mosaic. You have the result attached, it's better but you can see some parts blurred or in the top center above the entrance the stones are not at the good place.

How can I send you the project file ?

Alexey Pasumansky

  • Agisoft Technical Support
  • Hero Member
  • *****
  • Posts: 13913
    • View Profile
Re: fog on orthophoto
« Reply #4 on: January 10, 2013, 07:19:22 PM »
Hello lins,

Are you sure that there no misaligned cameras?

Have PM'd you about project upload details.
Best regards,
Alexey Pasumansky,
Agisoft LLC

RalfH

  • Sr. Member
  • ****
  • Posts: 344
    • View Profile
Re: fog on orthophoto
« Reply #5 on: January 10, 2013, 07:24:25 PM »
Hello lins,

around the "door" it looks like the alignment is not good. Could also be the case in other parts of the model. Try to fix that first.

Then, do you have closeup as well as overview photos in your project? If yes, this could cause the differences between sharp and not-so-sharp parts of the texture. You could try to build texture with the overview photos disabled.

lins

  • Newbie
  • *
  • Posts: 13
    • View Profile
Re: fog on orthophoto
« Reply #6 on: January 11, 2013, 06:34:06 PM »
Hello,

Sorry I couldn't download the files this morning. I am downloading one part, the models and few photos, now to the files Monument of Carn- Lins.  I will download the second part later.

I have one question but not for this problem. Photoscan is it working with photos taken by fisheye ?

Thanks

RalfH

  • Sr. Member
  • ****
  • Posts: 344
    • View Profile
Re: fog on orthophoto
« Reply #7 on: January 11, 2013, 06:39:45 PM »
Hello lins,

fisheye lenses are not modelled well by PhotoScan (or any other comparable software as far as I know). Some of the reasons can be found under "Mapping functions" in the Wikipedia article http://en.wikipedia.org/wiki/Fisheye_lens. You might get results, but it is much better to use a lens that is closer to formal focal length. This has been discussed in other threads in this forum before; the essence is: it is not a good idea, but if you have no other choice, you can try it.

P.S.: What focal length are you thinking about? (in 35 mm equivalent terms)
« Last Edit: January 11, 2013, 06:52:49 PM by RalfH »

lins

  • Newbie
  • *
  • Posts: 13
    • View Profile
fog on orthophoto
« Reply #8 on: January 11, 2013, 09:08:29 PM »
I asked because fisheye (less than 14 mm) is the best tool for my photos, here my photos have been taken with a 18 mm. The passage to go in the chamber is 60 cm large for 1 m high, so I don't have enough distance to take good pictures and the fisheye can be a good solution.

I know that MicMac, a french software, works with fisheye, but I don't know how. The french team wrote this paper : http://www.google.fr/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&cad=rja&ved=0CEwQFjAC&url=http%3A%2F%2Fwww.micmac.ign.fr%2Fsvn%2Fmicmac%2Ftrunk%2FDocumentation%2FDocMicMac%2FPaper-UseCase%2Fmel_isprs.pdf&ei=YlrwUNv-MYSp0AWmwoHYBw&usg=AFQjCNFX3vu1byv9a7PkyvP7M0IOTpL1lg&sig2=TkbnMwFRBJwmNPAKrdx99Q&bvm=bv.1357700187,d.d2k
« Last Edit: January 11, 2013, 09:33:05 PM by lins »

RalfH

  • Sr. Member
  • ****
  • Posts: 344
    • View Profile
Re: fog on orthophoto
« Reply #9 on: January 11, 2013, 10:51:18 PM »
Thanks for the link - quite impressive results they get out of a fisheye lens! And their software is open source and can be downloaded at http://www.tapenade.gamsau.archi.fr/TAPEnADe/Tools.html - I wish I had time to do some tests!

One thing I noticed is that they took many closely spaced pictures (one on each step of the staircase), which (when using a fisheye lense) results in much higher overlap than the 60-80% usually recommended for PhotoScan. In the (mostly unsuccessful) cases where I have seen fisheye lenses used for PhotoScan, such close camera spacing was not applied. So this could be a solution.
« Last Edit: January 12, 2013, 03:43:10 PM by RalfH »

Wishgranter

  • Hero Member
  • *****
  • Posts: 1202
    • View Profile
    • Museum of Historic Buildings
Re: fog on orthophoto
« Reply #10 on: January 12, 2013, 12:12:40 AM »
Lins have you at hands Iphone 4S or something similar ? try shoot the model with it, it will be possible to shoot in so small areas adn get good results.... Try tehn wil explain why its better....
----------------
www.mhb.sk

lins

  • Newbie
  • *
  • Posts: 13
    • View Profile
Re: fog on orthophoto
« Reply #11 on: January 12, 2013, 04:37:59 PM »
I don't have Iphone 4S or something similare and my monument is on island, so I can't got when I want...