Some of the atlases that I buy are known as large folio (or in some cases elephant folio) and trying to accurately scan the maps can be quite a chore. Whilst I have a ‘decent’ A3 scanner (Plustek OpticPro A320) the maps are still larger than the scanning bed, which means that I have to scan a map in two parts, either top/bottom or left/right depending upon orientation. I would then load each image into Photoshop, create a new canvas, and copy/paste each image into the new canvas, and manipulate them by eye to try and line them up. The results were not spectacular, and the process was very time intensive.
I looked for software that could automate this process, and initially used Hugin, following this tutorial – http://hugin.sourceforge.net/tutorials/scans/en.shtml – but again the results could be all over the place. Sometimes the preview worked, sometimes it didn’t, which meant running it ‘blind’. Sometimes the results were slightly skewed. Of course this could (or more likely probably) be all down to user error, but I went looking for another alternative.
The commercial software left a lot to be desired, and I was resigned to using Hugin, until I stumbled across a free Microsoft tool called the Image Composite Editor – https://www.microsoft.com/en-us/research/product/computational-photography-applications/image-composite-editor/ – which seems to have solved my issue. So if you are looking for a decent photo stitcher or panorama maker give ICE a try.