[ gpsdrive ] NOAA charts

[Hamish]

[cropping off chart collars for auto-tile creation from BSB RNCs]

Hamish:
> > perhaps r.reclass'ing white areas to NULL then 'g.region zoom='
> > to the reclass map?

maybe black too; then to remove specks either
- convert to vector and remove small areas
- stay as raster and use cluster / neighbor modules to highlight or
median-away small clumps

zoom to what's left as crop window then jump back to the original
image. I think it would take some tuning...

the easiest is to write a script with a human interaction "draw
zoom box now" step. but that's no good if you have to fix something
earlier in the process and have to do them all again. after 2-3
repeats you'd get a bit frustrated I think... n.b. the script
could save the zoom region and reuse it if present.

I guess we should try the automation way first, and if that is too
fragile or error prone fall back on the interactive method?
maybe a combo of both?


it's an interesting problem.


any idea what method the maptile GUI uses for collar removal?
256x256 is the standard tile size for UMN MapServer by the way,
which is why it is hardcoded to that. gpsdrive wants 1280x1024.

MapServer can mosaic the tiles in a singal canvas, gpsdrive can
only display one tile at a time (and so can't zoom out beyond the
tile).


Hamish