Hi all, GRASS 6.4.1 on ubuntu 10.04 64 bit, tcltk GUI (because of other wxpython probs previously reported)
Have been trying my hand at orthophoto georeferencing. I started with a digital image that was taken with a digital aerial camera. Has most of the camera settings required for the orthophoto parameters asked for in the steps. As the image is direct from the camera I didn't have a fudicial marks etc to do one of the steps but that didn't seem to be a problem. Seemed to be going OK, putting in parameters etc. Got up to option 7 (as per what shows in a terminal after i.ortho.photo is run from the GUI menu I have put in 4 control points using the monitor. For each one, i used zoom-box to get up closer before positioning point, and using keyboard to enter GCP co-ords. I then did a fifth point. it seemed to work OK, but then when trying to do zoom for another point, get messages: WARNING: Unable to find <raster_i_am_georeferencing> (click mouse to continue) [so i click mouse, then second message] WARNING: Unable to open raster map <ditto> (click mouse to continue) [click mouse again, options along bottom of screen come back, so I quit] I have tried repeatedly with fresh sessions of GRASS, to add more points without luck. Also noted that only four GCP's are saved. each time I start it up, I can apparently add GCP #5, and then get warnings after that, but that #5 point isn't being saved to the control points file. I tried a workaround: open up the GCP monitor/terminal, zoom and click a point, then go and open up the control-points text file and manually enter in that point co-ords and matching control co-ords. Go back to the monitor/terminal and hit 'enter' to blank out the point I'd just clicked on. Then tried zooming on another spot of the map, still got the errors. Opened up a fresh monitor/terminal, and noted that the point I'd manually added to text file was displayed correctly. Did a zoom box, actually missed where I wanted so then used zoom-point option to try and reposition the zoomed view, got the warning messages again. Dunno if it is part of same thing, but notice when I hit 'analyse' that the errors for east and north are up around 657900 and -6603200 respectively, using UTM 56J wgs84 (i.e. metres). target points are around 476900 and 7096500. It's a while since I've done some georeferencing, but these figures just seem too wrong. or does the error get calculated at the next stage and these are really just dummy/filler numbers? I tried another work around - run the 'georectify' tool from GUI menu, as far as the i.points part I think? i.e. enough to put one example point into the points text file. Then I copied the points from 'control points' text file for ortho-photo process, over to the points file for the regular process, noting the spaces, elevation etc that wasn't relevant for the points file. I could open that up in the georectify monitor, and the error shown for each of the points was more along the lines of 0.7 - 26 forward error and 5 - 125 backwards error (1st order rectification). That's hugely different from what I reported above in ortho-photo analyse. What have I done, that it was happy to input 4 points and after that I can't work it? If I have to manually add points to the text file, one at a time and restart i.ortho.photo each time, I will eventually achieve what I want. but that's time consuming, and absolutely not what the program was designed for, right? :-\ On the other hand, I could go back to what I've done before with the 'basic' georectify (i.points etc) but that won't let me add elevation data to an image like orthophoto does?? Regards, Shane. _______________________________________________ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
