What do you use to scan map?
Most of the maps in my collections are comparatively small (less than A4) and due to tight budget, I use a HP PSC1510 All-in-one printer-scanner at home.
I would prefer to use flatbed scanner as it causes damages as less as none. But when a map is larger than A4, I can only scan it in several sections and use Photoshop to merge. However it is quite difficult to scan a fairy large map (large than A3) with weak or even torn fold lines. Therefore, it is uneasy to merge the scanned sections together 100% accurate. For maps with simple design, it will be easier to match the scanned sections.
Mistake happened while scanning a large map, e.g. Children's Map of London (c1970s) 77.3cm x 57.7cm. I scanned this map in at least 6 sections and used Photoshop to merge. But there is one bit missing on the left and the scanned sections could not be perfectly matched.
This 'Plan of the Docks' (1964) is 85.6cm in length - for the map with simple design, it is more easier to match the scanned sections.
After reading the blog article 'What equipment are we using?'of State Library of New South Wales, I learnt that a CCD scanner Colortrac Scanner GXT 42E for large format prints. The museum I work at is also looking for a contractor who can scan large maps both antiques (e.g. 19th century blueback maps) and modern (Hong Kong harbour charts). It might be a good idea to have a scanner like this in the office.
Some large format scanner providers: