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I suggest you contact the restoration experts in major museums for (1) advice about preservation, and (2) how they go about their own digitizing projects. I read a fascinating article about the digitization of many medieval parchments, but I don't recall the particular museum involved now.

Obviously I cannot put those maps onto my 80 scanner and go. Some of them are really large (1.5m x 1.5m roughly, I believe) ...

I have a map of the U.S. - its actual size. The legend says "1 mile = 1 mile".
People ask me where I live and I say, "E4".

If so, give USGS a call. They may well be interested in helping you with this and obtaining data from the maps. I can't say for sure, of course, but this is the sort of thing they do. When it comes to map data for the US, they are the go to guys. Call them up, tell them what you've got and what you want to do, see if they can put you in touch with someone in their agency who'd be interested in helping.

You might want to find the local university cartography or geography department. They will probably already have a method of doing this, or at least could point you to someone who does. Here's an example: http://mapmaker.rutgers.edu/ [rutgers.edu] and their historical maps: http://mapmaker.rutgers.edu/MAPS.html [rutgers.edu]

-molo

Really, history majors will love this stuff. Giving them maps and a concept of Google maps overlays for real time comparisons to modern maps will likely be a capstone project for some undergrad.

A few years ago while working for the State of Wisconsin's Board of Commissioners of Public Lands we worked with the University of Wisconsin: Madison to get all of the original land plat maps of the state digitized, indexed and search-able. Same type of deal, huge maps on really old paper that had to be vault kept with humidity and temperature controls.

-Rick

Focus on the preservation of the imagery first, obviously, because once that's gone it's gone forever.

The cheapest option is a large-megapixel digicam known for good image quality. SLR would probably be a good bet. You can take multiple images and stitch them together without too much trouble, so you can get reasonably fine detail with a little work even with a $200 consumer camera. Or, alternatively, hire a professional photographer and have him/her take really high resolution photos of the maps. The advantage of this approach is that you don't have to take the maps anywhere or do anything special with them. Just lay them out on a low table or the floor and align a camera over them, and take heavily-overlapping shots.

Large-format scanners might cost some serious coin even to use for a one-time project like this, but would probably yield better results with less effort.

You might check with local companies that deal in maps and cartography, they might be able to recommend ways of saving the imagery, and some might even offer to help out if the maps may be of commercial interest (they might even share the proceeds with you in addition to giving you high-res digital images).

But I'd say if the maps are truly delicate, your first focus should be to take the highest-resolution images you can of them now, even if it's multiple images per map that need to be stitched. That way, you have *something* preserved in case one or more of the maps is destroyed or deteriorates further before you can preserve it.

If there are particularly interesting features of the map, use the MACRO feature on your camera - most stitching programs can integrate images at different scales and preserve a lot of detail. I used the "Hugin" pano toolkit (free) to stitch together about 100 random photos I took at the top of the Eiffel Tower into an impressive contiguous 360 panoramic shot, and it was literally a "here are the pictures, figure it out" process. The pictures were all taken at different zoom levels, different angles, and all sorts of issues, yet it looked like a Google Street View 360 image. This was 5 years ago, I can't imagine how much better the technology is today.

The geolocation shouldn't be all that hard - it's a matter of choosing a few points on the map and identifying their coordinates accurately. Of course, if there are few/no reference points it gets a lot harder. http://www.openstreetmap.org/ [openstreetmap.org] is a good starting point to a group that does free, open-source mapping. They or some of their related sites might possibly have a tool that does what you want. Also, a professional cartographer may be able to help you out as well.

First, ask on the OpenStreetMap mailing lists. There's lots of us who've done this kind of stuff before, and we'd be really pleased to help. I collected, scanned and rectified the Ordnance Survey's New Popular Edition - a complete set of England and Wales maps from the '50s, now out of copyright. It's all available in OpenStreetMap as a background layer and loads of people use it for adding rural roads, rivers, placenamese etc. Others are scanning other old Ordnance Survey series right now. Seriously, we love this kind of stuff. (#osm on OFTC can help too.)

Secondly, GDAL [gdal.org] is definitely your friend. It's the most amazing set of command-line tools for rectifying and reprojecting data. gdalwarp and gdal_translate are probably the two you'll use most.

Take photographs of them and put them on the internet. Google will automagically index them and add them to their street maps in real time.

Hi there, I am a spatial guy so thought my 0.02 may be worth something. I am not too sure about digitising them, maybe a print shop or as suggested in other posts you could talk to your local university geography department or a government mapping agency

Once they are digital though you need to georeference them. As mentioned in the title of my post, it is easiest to use GIS to do this and you can use QGIS with relative ease. Install it using osgeo4w [osgeo.org] on windows or the ubuntu ppa for qgis [launchpad.net]. Alternatively if you have a license then use ArcGIS. If you have a map of the underlying roads for the maps you are digitising then what you do is find points on the roads and match them to points on the scanned images, this provides data for a transformation and will shift the map onto your coordinates.

I spent a summer doing this in grad school for the Vegetation Type Mapper [berkeley.edu] project at UC Berkeley. I'm not going to lie to you--it was a ton of work. But the results were cool. The site has all the old maps georeferenced, plus ways to download them.

Needless to say, the library was involved in the project, as was a giant scanner. We relied on ERDAS Imagine software to georeference the old maps to current USGS base maps. There was also a lot of accuracy assessment involved to make sure we minimized error in the georeferencing process. Probably one of the trickiest parts was making sure the old landmark you were using as a control point had not substantially changed in the intervening decades.

My professor and her colleagues published a paper detailing the project [berkeley.edu].

Others seem to be describing some good solutions to getting the map scanned, so here's how to geocode and rectify the image using the open source Grass GIS software:

Step 0:

- You need to have a location already created in grass, with some contemporary data in it (physical features, roads etc where there's some concurrence with the map you're trying to geocode). The projection you've used doesn't matter much - a later step is going to be rectifying (ie distorting) the scanned map to match the projection of the digital map. The created location does need be at least as large as the scanned map (ie if the map is everything in a 5 km radius of some town, the grass location also needs to encompass at least a 5 km radius of the same town).

Step 1:

- Come up with a list of features/points which exist on both maps. Depending on the scale of the map, this could be intersections of specific roads, locations of towns, peaks of mountains etc. You're going to need an absolute minimum of five points for the rectification process to have any chance of working; more than fifteen is much better. Try and select points which are unlikely to have moved over time (coastline or river features for example). In grass, mouse over each point and record the coordinates.

Step 2: import the scan

In grass, do: r.in.gdal input=[path to scanned file] out=[Mapname] location=templocation

Quit grass

Step 3: target, point, rectify

Open grass, but this time in the 'templocation' you created in step 2

i.target group=groupMapname location=[modern map location name] mapset=PERMANENT
i.group group=groupMapname in=Mapname
d.mon start=x0
i.points groupMapname

d.mon will open a window; i.points will display the scan in it. Select the mapname in the dialog that appears, then one by one select each of the points you've identified as having concurrence with the modern map. In the terminal window, enter the coordinates for the point taken from the list you created in step 1. When done marking points, click 'quit'.

i.rectify -a group=groupMapname extension=_1 order=1

Depending on the size of your map and your processor speed, this bit may take a while. When done, quit grass.

Step 4: admire output

Open grass in the modern location. The scanned map will be available as a raster layer for display. The scan will have been rectified so the map matches the projection of the modern map layers - ie you'll be able to see what's moved and changed, and what exists now that didn't then etc. There's other grass commands which will help you convert features of interest (rivers, roads, contour lines, whatever) into vectors if you really want.

If all this seems too hard, have a look at qgis - also open source mapping software; it's more gui-oriented and I know it has a georectifying plugin. I've just never used it.

Good luck.

Contact a local Licensed Land Surveyor. We are in the business of coordinating maps and making sure they are properly referenced. We also know the difference between NAD83 and NGVD29. This and the other coordinate system conversions and the proper use of scale factor in SPCS (State Plane Coordinate Systems) is something we do every day. Plus, most of us are really into local history and could possibly show you some other really neat uses for that data. Historic societies are always looking for ways to map past events. When speaking with a Surveyor, we can usually know what the practice for a given time period was. There are three different lengths for a foot that I have come across working. International Foot (not used in surveying, but sometimes engineers use the wrong foot), US Survey Foot (standard) and the Philly Foot. Philadelphia has a different set of standards for how a long a foot is, depending on what part of the city you are in and what you are trying to do. This is not something most historians would accurately pick up. Surveyors will. We also know who was the good and not so studious Surveyors in the area and what tricks each used to mark corners, turning points and reference markers. A local Surveyor in the area the map is of would be very interested in helping you with your work. He/she may have already done the heavy lifting for you. We have to trace maps back as far as possible, so sometimes (I am in New Jersey) we have to go all the way back to the Proprietors to get maps so that we can run lines that control our current work.

Long story short, if it deals with cartography or local surveying, seek a professional Surveyor.

I have done this for a grant-funded historical map digitization project at a university library. We used a $40k large-format scanner (from Betterlight) which can scan the whole item laid out flat. Trying to stitch together camera images will result in distortion across the image—if you didn't need to distort it, you wouldn't need special software to do it; you could just line the pictures up.

But even once you have image files, there's about zero chance you can just replace Google Maps' tiles with your own and expect geotagged stuff to line up where it should. If you have a finite number of places of interest, you could manually locate them on each map and then try to distort each map to align, but if you expect arbitrary geolocations to need to be right, give up. Non-satellite/GPS-based maps are examples of practical cartography, not theoretical. They will be even less perfect than you think, no matter how professional they appear. Or do what we did: keep the geotag display on Google's maps, but show your historical map of the same general region side-by-side and allow the user to calculate the precise correlation in his own brain.

I can't speak on how to get them digitalized, but once you do, look to the web to get others to help geocode and get them into shape for overlays. Put them online in a liberal CC license and invite other people to use them. Given the popularity of google maps and the community that's grown up making mashups and apps, I'd be willing to bet there already existing communities of people good at, and interested in, doing this.