On Mon, Aug 17, 2015, at 08:43, Blumentrath, Stefan wrote: > Hi Markus, Florian, and others, > > Thanks for your replies. I still did not solve this, so I am grateful for > any hint.
Could you maybe apply a two-stage process where you first correct (at least partially) the perspective distortion and then do an orthorectification on the result? I don't think that the GRASS georeferencer has a perspective/projective transform, but QGIS does. (In case anyone wants to implement the projective transform in GRASS: I have made a plain C translation of the QGIS algorithm available here: https://svn.code.sf.net/p/gvsigce/code/trunk/libraries/libCTL/ -- requires GNU Scienfic Library for the matrix algebra.) Best, Ben > > Now, I extracted the relevant data (XY-location containing the mapset > (“reconyx”) with the image group (containing i.ortho.photo files), and > camera file as well as the target location (“ETRS_32N”) with the “target” > mapset containing the DEM (“dem_1m”) and two of my attempts for > orthorectification (with and without INIT file active). You can fetch > the zip-file with the GRASS DB (22 MB) within the next 30 days from: > https://www.dropbox.com/sh/swri19zn5m9gb7w/AACADlkqGZKO_JMS_YbLNXBXa?dl=0 > There you will also find the original image (“IMG_0015.jpg”) as it comes > from the camera. > > As a next step I will take another test image with a more orthophoto-like > perspective and no visible sky. I hope, that way I can check whether the > issue is due to the chosen camera position / angle or the way I defined > the exposure in the INIT file… > > I have a strong feeling that my problems - in one or the other way - have > to do with camera angles… > > Unfortunately, it does not seem to be possible to specify only the > exposure parameters one is sure about. i.photo.rectify uses either all or > nothing to initialize the orthorectification algorithm… > > Cheers > Stefan > > From: [email protected] > [mailto:[email protected]] On Behalf Of Florian Mueller > Sent: 15. august 2015 20:54 > To: grass-user grass-user ([email protected]) > Subject: Re: [GRASS-user] Orthorectification of tilted digital camera > images > > Dear Stefan, > > Can you provide some example photos in a Dropbox (e.g.) folder? > > Best regards, > Florian > > > On Sat, Aug 15, 2015 at 7:53 PM, Markus Neteler > <[email protected]<mailto:[email protected]>> wrote: > On Tue, Aug 11, 2015 at 11:37 PM, Blumentrath, Stefan > <[email protected]<mailto:[email protected]>> wrote: > > Dear all, > > > > Although there is a lot of relevant information regarding the > > orthorectification of tilted digital camera images in GRASS GIS online > > (here: > ... > > Does up-slope direction of the photo or sky in the photo conflict with the > > orthorectification algorithm? > > I have no idea... in general the algorithm is very robust but was > really written for aerial photos. > > > > > When it comes to the GCPs I am in principle quite confident that they are > > placed OK. Or do you think that GCPs measured by a hand held GPS are too > > imprecise? > > They should be fine. > > > However, depending on initial camera settings RMS something like 268, which > > indicates that something is wrong here. If I do not use i.photo.init, the > > image is placed much better (RMS around 10-20), but still pretty poor… > > About 10 years have passed that I tried the last time, memory is > fading... > > Did you figure it out? > > ... > > Btw: Some of the submodules of i.ortho.photo are not linked to the /bin > > folder in GRASS 6.4.5svn, so I have to start them like this: > > /usr/local/grass-6.4.5svn/etc/i.photo.init > > To my knowledge they are intentionally hidden in order to be run from > the i.ortho.photo main menu (in GRASS GIS 6). > > Markus > _______________________________________________ > grass-user mailing list > [email protected]<mailto:[email protected]> > http://lists.osgeo.org/mailman/listinfo/grass-user > > _______________________________________________ > grass-user mailing list > [email protected] > http://lists.osgeo.org/mailman/listinfo/grass-user _______________________________________________ grass-user mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/grass-user
