[GRASS-user] Re: [CREATE] Lens correction database

GRASS GRASS user
1

Hi,

[ x-post on purpose. reply-to set to create@lists.freedesktop.org ]

Wed 07 Nov 2007 20:42, Andrew Zabolotny wrote:

After more than two months the first release of the lens database and
library is out for alpha testing. Anybody interested is invited to look
and comment on it.

wow! this is pretty great. you guys rock :slight_smile:

basically all this lens+camera "defect" modelling is also very useful in
the geomatics/remote-sensing area. (of course also in computer vision,
medical imageing, etc.)

i had a quick look @ http://lensfun.berlios.de/manual/elem_calibration.html
and also read in the ML archive the high-quality disscussion you guys
had. (lot's of useful info there!)
e.g. http://lists.freedesktop.org/archives/create/2007-August/thread.html
http://lists.freedesktop.org/archives/create/2007-September/thread.html#932

Since this list is not the best place to flood about it,

agreed!

I propose all further discussions to be moved to the dedicated berlios
forum and bug/patchtracker.

mmh, maybe an new mailing list, dedicated to photogammetry?
basically we share the very same problem, but our practical realisations
of a camera/sensor are quite broad. e.g. a DSLR camera has a tiny
CCD-sensor on it's back-plane, while a professional aerial camera has a
back-plane of 350mmx350mm, etc..

e.g. on the geomatics/remote-sensing side OSSIM ( http://www.ossim.org ),
also already has support/code for lens correction for modern aerial cameras
(but basically that's the same. lens-correction is useful for all
cameras/sensors with lenses :slight_smile:

GRASS GIS ( http://grass.itc.it/ ) on the other hand does not even have
lens-correction support at all it appears. ( yesterday night i was wading
throu the code, i couldn't spot any. feel free to correct me.
http://freegis.org/cgi-bin/viewcvs.cgi/grass6/imagery/i.ortho.photo/ )

My plans is to start adding support for it into UFRaw.

great. so with ufraw-batch it will be possible pre-process aerial photos
(which were shot with a DSLR camera) to rectilinear, and when further process
them in GRASS. looks good.

I hope this real-world usage will show the weak points of the library, especially
because in UFRaw it will be a very untypical usage (applied on a bayer
image).

cheers,
s.

2

hi,

[my last x-posting on this topic. reply-to set to
create@lists.freedesktop.org again; in the lack of a
list dedicated to this topic.]

Tue 08 Jan 2008 16:23, Andrew Zabolotny wrote:

From Tue, 8 Jan 2008 11:36:53 +0100
sebastian sauer <scb@lo-res.org> wrote:

> basically all this lens+camera "defect" modelling is also very useful
> in the geomatics/remote-sensing area. (of course also in computer
> vision, medical imageing, etc.)
I wasn't looking that far :slight_smile: My guess is that specialised applications
use cameras/lenses far from regular photographic equipment,

to make it less confusing, i'll make it simple :slight_smile:
basically there are 2 widely used FOSS geomatics programs GRASS and OSSIM,
and basically 3 different user-groups.

1/ people with really fat cash, having access to high-tech *modern* aerial
imaging equipment. (fuckin' expensive, really)

OSSIM supports this stuff..
https://svn.osgeo.org/ossim/trunk/ossim/src/apps/applanix2ogeom/
applanix2ogeom supports non-linear discrete radial lens distortion.
basically you specifiy a parameterfile, which you get from the camera.

2/ people with still quite some budget, having access to old, classic
aerial photo-cameras.

..these cameras vary, but the higher-end modles among them are like that..
http://erosproject.cr.usgs.gov/osl/acspecs.html
http://erosproject.cr.usgs.gov/osl/reqtable.html
http://erosproject.cr.usgs.gov/osl/sixspecs.html
http://www.environment.sa.gov.au/mapland/camera_types.html

GRASS supports them, but AFAIK assumes that the images are rectilinear.
http://grass.itc.it/grass63/manuals/html63_user/photo.camera.html

3/ "ordinary" people that shoot with some standard of-the-shelf, over-the-counter
DSLR, (often with wide-angle / fish-eye, in the hope to get a similar field-of-view
as a professional aerial camera.)

these ppl. somehow not yet realize that exactly e.g. your software will help
them :slight_smile:

e.g. this GRASS user, which for some reason decided to ignore me and my
comments..
http://lists.osgeo.org/pipermail/grass-user/2008-January/042487.html
http://lists.osgeo.org/pipermail/grass-user/2008-January/042496.html

.. see also there's a whole new generation comming, very cool..
http://openaerialmap.org/

and one of the god-fathers of FOSS geomatics Markus Neteler posted also
a very usful paper and a wiki-page..
http://lists.osgeo.org/pipermail/grass-user/2008-January/042494.html

I'm wrong. In any case, I think lensfun will need some improvements to
be useful in that area.

fact is, you guys here on this list are the actual experts on
lens-models. believe it or not :slight_smile:

GRASS GIS has nothing for lens correction.

and OSSIM has decent models (what can compare well to commercial
geoformatics software) *but* nothing really advanced.
"OSSIM does have sensor models for aerial frame and pinhole cameras.
A full blown camera model will have calibration information such
as focal length and radial distortion parameters."
http://sourceforge.net/mailarchive/message.php?msg_name=0DDA504E-3A89-42EF-A81E-1EC4398C80B3%40mac.com

> mmh, maybe an new mailing list, dedicated to photogammetry?
If you can find more than two interested people, maybe it makes
sense :slight_smile:

agreed. maybe the Vision Workbench software makes it more clear how much
overlap we have on this topic..
http://ti.arc.nasa.gov/visionworkbench/

But in any case my primary interest is photography, so I can't
tell much on the subject you're interested in :slight_smile:

sure, this also doesn't matter. as far as only lens / camera "defects"
are our interests are the same.

also a side topic could be semi-automatic camera-calibration (that means
semi-automatic dedection of e.g. the lens parameters) as there is
already some decent software.
http://www.vision.caltech.edu/bouguetj/calib_doc/
http://graphics.cs.msu.ru/en/research/calibration/index.html
http://opencvlibrary.sourceforge.net/

..but this stuff could be added later to lensfun, as an alternative or
enhancement to the lens database.

cheers,
s.