I am trying to create raster images of maps which are too big for my scanner.
Using i.points and r.patchh with i.rectify to fix orientation and position.
The reassembly works almost very well, but I have a scouple of problems:
- There is an error of a millimeter (5-10 pixels) near the seam which
looks bad. This is despite zooming in fairly closely (point +2) when
marking the points.
- The part upon which I run i.rectify (to adjust orientation and position
automatically) looks less sharp than it did originally.
Generally, I am wondering if i.points3 and i.rectify2 would be better for
adjusting, potentially, position in x/y, rotation, and a tiny amount of
scaling so that the seam will be clean. If so should I be trying for a
first, second, or third order adjustment?
A separate application I have is to correct old, inaccurate maps, which are
generally pretty close over large areas but which have numerous local
inaccuracies. In this case recification should ideally performa a best-fit
for the overall image, and then apply ocal corrections in small areas to fix
particular points, such that the local corrections "fade away" with distance
so as not to influence faraway points (other than via the betst-fit).
I have an additional problem with ipoints3: I seem unable to tell it that I
wish to enter points via the mouse vs. the keyboard; when I attempt to do so
the program seems to hang. I am using an April grass5 beta.
David C Niemi