Outdoor maps tend to be too large to be easy to use when climbing (or trekking for that matter). Copying or scanning & printing smaller portions of maps is often a good idea to create a map that is easier to manage. This can also save some money, as you are less likely to tear or otherwise destroy the original map.
Copying parts you actually need is obviously simple enough, but there are times where scanning is useful (particularly if you want to add route lines, campsites etc. on a map beforehand. However, scanning large format map raises few issues:
- unless you have access to large format scanner, scanning in parts & stitching the pieces is required
- folds and wrinkles are as good as certain to cause distortions. It is also virtually impossible to get the map to be completely flat on a scanner, which causes more distortions. And finally, scanners, particularly inexpensive ones, can add distortions of their own.
The best way (here: best equals the method that produces the best results, not the method where you might get acceptable results with least amount of time and effort) to scan maps for stitching I have come up with is the following (warning: the process is labor intensive; so if you can get the map in digital format, do yourself a favor and get it to save a lot of hassle).
- Get the map as flat on the scanner as possible. This can often be achieved removing the lid and placing heavy book above the map.
- Scan each piece normally. usually it's a good idea to leave edges unscanned, as they are almost certainly not completely flat causing bot distortion and darkness.
- Despite all the efforts described above to avoid distortions, there are some, trust me. Distortions are particularly bad for stitching as they are sure to cause disalignment on the part edges. The way to fight this is to:
- create a grid and distort scanned image back to the size and shape it should have been. In the case of maps there are usually gridlines. The idea here is to create grid using image manipulation applications guidelines tool so that the grid size is exactly as it should be on paper map.
- then load each of scanned images as new layer in image processing app and force it back to shape by distorting it so that the grids on map align perfectly with grid created above with guidelines. This also takes care of deskewing the scanned image (it is virtually impossible to scan large format originals with smaller format scanner without the scan to be a bit rotated).
Obviously one could try to be lazy and use stitching application for the same purpose and thus save a lot of manual labor. However, I have found that they usually do a bad job of stitching maps. No reason not to give it a go though.