[Talk-GB] Stitching Aerial Photographs

John Robert Peterson jrp.crs at gmail.com
Sun Sep 20 21:49:39 BST 2009


ok -- now we are getting somewhere -- this is awesome.

I would sugest rectifying against the gps trace data, not the map layer,
because the positions on the map later are derived, introducing slight
inacuracies.

Do we have anything that will draw map tiles of the trace data? (I'd like
this for another project anyway: checking whether traces exist for an area
when out with a mobile device)

now hugin/panarama tools/sift has a strong concept of control points, so
does warper -- is there any way that we could get them to use the same
points, and bolt the 2 together automatically?

nearly a week ago I posted the following, any further thoughts on it:

The ideal situation for me would be if we could have some automated tool on
a sever somewhere receiving images from users, and automatically rectifying
them.

This sounds imposable, but I believe that with a very small amount of user
help it could work:
Images can be automatically pinned together in overlaps (and high res images
can be pinned onto wide area images) using tools similar to those in
Panorama Tools / hugin (this searches for notable points in the image data,
and matches them between images);
searching the images for road markings (and/or cars) and matching these to
the gps traces already uploaded would give a reliable enough way to add real
world control points;
if a concept of altitude is added, automatic control points between images
appearing on top of skyscrapers would not be too damaging;
approximate terrain relief for most of the planet is already known, this can
be tied into the above to help;
manually adding control points would be done by displaying already rectified
images next to a map, with the user adding pins to useful points;
images with no rectification data at all would be added using a push pin
system similar to that used on http://warper.geothings.net/

the above is a pipe dream at the moment, but has the potential to
revolutionise how we do things in my opinion.

JR

2009/9/20 Matt Williams <lists at milliams.com>

> I've been having a go at rectifying some images with the Geothings
> Warper and I've covered about half of Tiddington. They're public on
> the website as numbers 1310, 1307, 1309, 1312, 1313, 1311, 1308 (in
> that order, most vertical first). However, there are very obvious
> seams between images. This got me thinking about the possibility of
> creating a panorama image to actually stitch these images together.
>
> Hugin is an open source panorama program (which I believe uses parts
> of the SIFT algorithm to match features) which can do a very good job
> of stitching the images we've collected together. I had a practice
> with images 00822-00825 and very successfully was able to stitch them
> together with no visible seam at all. I then uploaded the composite
> image to Warper (http://warper.geothings.net/maps/1315 or the original
> higher-quality image at
> http://warper.geothings.net/uploads/1315/original/test3.jpg) and
> rectified it. However, the recfication in this case probably isn't
> good enough due to the slight warping caused by Hugin.
>
> What we really need is a Hugin-type application which allows you to do
> the standard stitching thing (setting control points between photos)
> while at the same time allowing you to match points on the photos
> against points on a map such that when it creates the 'panorama', it's
> automatically rectified too. Does anyone know of a way to utilise
> Hugin or Panorama Tools (upon which Hugin is based) to do this sort of
> thing? I imagine it's not been done exactly like this before but I'm
> sure there must be a way.
>
> The long way to do it (and I'm not really suggesting it) would be to
> warp each individual image in Warper, then stitch the warped images
> with Hugin (at this point they should almost match the map) and then
> finally re-Warp them again to neaten them up. The problem with this is
> that Warper only produces low resolution images which wouldn't work
> with Hugin very well.
>
> Thoughts/suggestions?
>
> --
> Matt Williams
> http://milliams.com
>
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> Talk-GB at openstreetmap.org
> http://lists.openstreetmap.org/listinfo/talk-gb
>
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