On Fri, Oct 23, 2015 at 10:17 AM, Moritz Lennert < mlenn...@club.worldonline.be> wrote:
> On 22/10/15 16:25, Johannes Radinger wrote: > >> Dear GRASS users, >> >> Today I wanted to try the georectification tool g.gui.gcp in GRASS 7 for >> the first time. I was basically following the description on the GRASS >> wiki (https://grasswiki.osgeo.org/wiki/Georeferencing). In particular, I >> have a photograph from my camera with known reference points which I >> load into an unprojected XY location. My target location should also be >> a XY location as the picture is taken from a "virtual" coordinate >> system. Inside my target XY-location I try to open g.gui.gcp and select >> raster, and the location and mapset where my photograph is stored. When >> I want to click next I get following error/message: "You must select a >> valid location and mapset in order to continue" and I can't proceed with >> the rectification. Just this GUI message appears, no error/warning in >> the grass console etc. I am puzzled how to interpret that? What is wrong >> with the location/mapset? The mapset I've selected is existing (I can >> select it from the dropdown menu). I tried to select any other >> location/mapset but receive always the same message. >> > > > Georectification is for georeferencing to a projected system. It does not > make sense to georeference to an XY-location. > > I see two options for you: > > - Import you image directely into the target region and use r.region to > adjust its boundary coordinates > - Define your own projection system to fit your needs. So far as I understand georectification and orthorectification in particular is to rectify a picture/photo/image based on spatially defined ground control points which might not be done by just adjusting the boundary coordinates. BTW I also tried the European LAEA coordinate system (EPSG 3035) as a target location which is not working either here in my machine/setup (same message as already mentioned). Here ( https://www.dropbox.com/s/snjzd8eu7b8115k/2015-10-22%2015.26.30.jpg?dl=0) you can find a a photo (*.jpg) which is an "areal" photo with known 3d coordinates for the single points (ground control points). I think this example clarifies and illustrates what I intend to do and why the target system can also be a XY location in my opinion. A rectification of this image should make the lines of the grid more or less parallel. Or do I get something completely wrong? /Johannes > > > Moritz >
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