2 replies to this topic

[Sam Wren]

I need to produce some relatively large-scale maps for some historical projects on which I am working. I have no cartography, graphic design or art background. My computer is a Mac, I have a scanner and Photoshop Elements 4.0. I would like to not have to buy more software but have not figured out how to do what I need to do with Photoshop. Because my maps will need to reflect road systems and geography during 1940s, I cannot use GPS-based software nor can I use modern-day maps without extensive alteration (I assume). I have several maps of varying quality and scale which cover the area I need, but how to condense them into one single map without hand-drawing (at which I suck)? I have done a fair amount of research into the subject but all of the sources I have been able to find are based on GPS data. I am hoping that some patient soul will have pity on my ignorance and at least point me in the right direction.

Thanks in advance,
sam

[Hans van der Maarel]

I need to produce some relatively large-scale maps for some historical projects on which I am working. I have no cartography, graphic design or art background. My computer is a Mac, I have a scanner and Photoshop Elements 4.0. I would like to not have to buy more software but have not figured out how to do what I need to do with Photoshop. Because my maps will need to reflect road systems and geography during 1940s, I cannot use GPS-based software nor can I use modern-day maps without extensive alteration (I assume). I have several maps of varying quality and scale which cover the area I need, but how to condense them into one single map without hand-drawing (at which I suck)? I have done a fair amount of research into the subject but all of the sources I have been able to find are based on GPS data. I am hoping that some patient soul will have pity on my ignorance and at least point me in the right direction.

Well... where to start...

First questions:

• Which area are we talking about?
• What scale/size would you like your final map to be and what scales are your reference maps?

If the scales are roughly the same, you can probabely get by with mosaicking them and then either using that mosaick as-is, or use it as a reference to manually draw new features. If the scales are wildly different, you can still use them as a reference when drawing the map, just make sure you generalize where appropriate.

This does however assume that your reference maps are all in the same map projection (and that that map projection is also the one you'd want to use on your final map). If it's not, you've got a problem. You'd need to warp the projections into a common one before you can mosaick, and that process is, at best, very very difficult in Photoshop (and potentially impossible). In that case you would need specialised GIS software (and some knowledge on how to use those). Even then, it's probabely going to be rather tricky to get everything lined up properly... However, if they are the same scale, you can just copy/paste them onto different Photoshop layers and manually position them.

In order to be able to mosaick your reference maps, you need to scan and then georeference them. This fixes their position in a global environment, allowing GIS software to combine them with other georeferenced data. When scanning, try to get as large an area as possible onto every scan and include all of the collar information (because if often contains vital clues as to what the projection is). If you have to scan every map in segments, make sure they overlap generously. Try to get the map as flat (and as straight!) as possible on the scanner, and make sure you put north up all the time. In case you're scanning in segments, georeference/mosaick everything for a single map first, then join them all up.

Hope this helps. Feel free to ask if you have any more questions (and please keep us informed of your progress).

What you may want to do, once you have some maps scanned, is post them here and see if anybody is willing to help out with the georeferencing and mosaicking (I might, depending on time/availability)

[Dennis McClendon]

The way this is usually done is to work in Adobe Illustrator or FreeHand, tracing over the relevant lines and features on the old maps scans (which have been placed on a background layer that will later be removed). This may sound daunting, but is much less work in the long run than trying to clean up linework or remove extensive features in Photoshop.

Give a few more details about the subject matter and how you plan to use the finished maps, and we may be able to offer more help.