Hi again all, I'm trying i.ortho.photo from wxGUI to assess an earlier problem. So far I have hit a similar error message when zooming after a few GCP's are present, but I am wondering if I have done some things wrong in earlier steps.
For entering camera position at step 6 for omega/phi/kappa, I read the help/instructions in GRASS, and based on having the camera pointing straight down from the plane, I put the angles for both of these at 0. The instructions state that I don't need this step when using vertical images anyway, but for the sake of me understanding how this whole process works I wanted to enter the values (and can just leave 'use at run-time' set to 0). Should I actually have used 90? My interpretation of the instructions may have been wrong in assuming zero is when camera view is perpendicular to ground in the x and y planes. Is camera angle for these values measured from horizontal? Then, if there is roll or pitch, do either of these have a positive/negative or clockwise/counterclockwise format? the instructions explain yaw is measure in degrees from north, clockwise being positive (but not full 360; goes to +180 or -180)? Another key thing I may have shot myself in the foot with, is editing original image. It was too big to use in entirety, so I cropped out the section I wanted in the middle. I also increased resolution of this cropped bit to give a clearer picture. So whilst dimensions have changed, it is not the extent of image that is indicated by original camera specs e.g. focal length, width/height, pixel dimensions will be different. Does this mean the use of orth-photo rectification is voided for me? Or can I employ some trigonometry and basic maths to calculate parameters for the cropped image from the parameters of the original image and then feed those into i.ortho.photo? Comments appreciated. Regards, Shane. PS, on similar note, another poster asked about using ortho-photo rectification of satellite images, to which the advice was 'you can't'. I would have thought a satellite image is akin to an aerial image taken just a little higher off the ground...?? or do sat images span too much curvature of the earth to rectify well in i.ortho.photo? or do they lack the parameters required such as camera angles, focal lenghts/points, etc? _______________________________________________ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user