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Digitizing and Geocoding Old Maps?
alobar72 writes "I have quite a few old maps (several hundreds; 100+ years old, some are already damaged – so time is not on my side). What I want to do is to digitize them and to apply geo-coordinates to them so I can use them as overlays for openstreetmap data or such. 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) and they need to be treated with great care because the paper is partly damaged. So firstly I need a method or service provider that can do the digitizing without damaging them. Secondly I need a hint what the best method is to apply geo coordinates to those maps then. The maps are old and landscape and places have changed, it maybe difficult to identify exact spots. So: are there any experiences or tips I could use?"
Why not use a handheld scanner and some stitching software?
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.
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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".
It must have been something you assimilated. . . .
I'd suggest appealing to Google or the brothers that did tapestries for the Met. What are these maps of? Is there a society for the place that they cover where you could appeal for funds under the pretense that you publicly release the maps?
Assuming all those avenues are exhausted, let's look at some cheap and dirty DIY methods. I'm assuming you've got a MP digital camera. There are sub $100 ten megapixel cameras out there but don't get anything with a fancy digital zoom. Next you'll need mosaicking software or if you're into software, you can try your own implementation of the KLT algorithm.
First off, practice all of this on layed out newspapers while developing your preferred methodology.
Your cheapest and most haphazard option is going to be lay the maps flat on the floor and cut a length of string with a washer on it (two to three feet?). Try to use brightly diffused lighting so that is normalized in the mosaics with no shots of your shadow over the maps. Now this is backbreaking but hold the camera flat over the map with the string extended in front of it so you can keep the distance to the map consistent. Don't angle the camer as this will slightly distort that tile and hinder the mosaicking. Put plastic bags on your feet if you need to walk on the maps. Take a picture, move a few feet in a grid style, take another picture. Rinse, wash, repeat until you have images covering all of the map. Collect the images and put them on the computer and verify the mosiacking works before preparing the map for storage forever.
A better method would be similar but to construct a large wooden rectangular box with plexiglass as a top so that you can fit this structure over the largest of the maps. Then cut holes in the plexiglass so that you can set your camera at a plane level to the surface of the map into the plexiglass. You might want to put an adapter on your camer that allows the lens and flash to be free of obstruction. You could make the tiles more uniform and save your back some work but you need to build and buy the materials for the structure. I think this is more time consuming but your best bet and will allow you to gather more images with less distortion.
Above all, remember to save the original images! It's probable that later better algorithms will be developed to normalize the images, remove distortions, light problems, shadows and increase clarity on your overlapping sections. If you do the plexiglass route, you could manufacture it so that every bit of the map is photographed three or four times.
Not professional, not flawless but cheap and dirty. Hope this helps.
As for the geocoding, what are the maps of? You should actually check out the feature extraction of the KLT algorithm and consider using that methodology for syncing these up with maps. That will require human intervention though to identify the features, I'm sure.
My work here is dung.
I actually have a strange fascination with old maps myself, and regularly crawl the web for all kinds of antique maps. One overwhelming commonality I have noticed is that even recent maps can often be wildly wrong. So for example, an 1600ish map of Europe will be so wildly inaccurate that you would only be able to pick one point on that map to apply geolocation specific coordinates, the rest would not match up. So, I know I didn't answer your question, but I just think that unless they are accurate maps, it would be a very hard challenge.
"It's ok, I'm completely secure as long as my iron is off"
I doubt it's in the US :) Based off the currency he used for his scanner (€80) I'd say that he's somewhere in Europe :) Good suggestion though. I wonder if the country he is in (or Europe in general) has a similar organization.
Vivin Suresh Paliath
http://vivin.net
I like
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/ and their historical maps: http://mapmaker.rutgers.edu/MAPS.html
-molo
Using your sig line to advertise for friends is lame.
Been there, fought lighting and camera distortion for hours, only to get bad quality (relative to a scanner)
Lay the maps out on a uniform surface, take the lid off a nice scanner and turn it upside down and move it place to place. Use rather big (1-2inch) overlaps, because the edges of the scanner sometimes are incorrect. You can make a batch process to crop the edges off in photoshop / gimp.
Most important is to lock down scanner settings so nothing is auto, or you will have colorcontrastluminosity differences between sections of your map.
Stitching these together requires 0 effort in any modern photographic editing software.
This is cheap, gives the best results and is the only way to get good quality without spending a fortune or damaging the documents.
Another possibility would be a really high resolution digital camera. My wife (historical linguist) has dealt some with manuscripts, and that was their method of digitizing them for further study. OTOH, she's not a museum curator or archivist; they probably have even better methods. If you want to do it right, talk to a curator or archivist of some sort. They deal with much more fragile and much more valuable documents on a regular basis.
I don't have any good ideas to contribute about the geocoding, unfortunately.
SIGSEGV caught, terminating
wait... not that kind of sig.
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 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.
Like the beaver, it's just Dam one thing after another
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.
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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.
For best results generally you would use a SLR with Macro lens. This type of lens generally provides the flattest field at reasonable cost even when it is not used in macro mode.
Then you've got architectural lenses, but those cost an arm and a leg and a foot - but then again, renting is always an option...
Just a pedantic little thing -- as a geomorphology instructor, I can tell you that rivers and coastlines are very, very likely to have changed. Check out pretty much any river mouth in Victoria, Australia, or any island off Maine, US in google earth vs google maps satellite mode for examples of how much they can change inside of just a few years. If something catastrophic has happened (big storm, big earthquake...), huge changes can shift the coastline inside of hours.
If you're going to use geomorphic features for your geocoding, find out what's most stable in your region (keyword search academic journals for geomorphology + your location + change and see what doesn't pop up, or ask a local university geo prof). Vegetated topography can be pretty stable over decades, especially if you only need relative shapes.
no macro lens.
What the OP needs is called a large format copy stand.
You want a lens that is "normal" to your film size, thus 50mm on 35mm film as an example.
for an APSc size sensor in a digital camera I think the normal lens would be ~30mm.
I don't know if you want color information or not but honestly either way I would shoot film, then scan the result.
For B&W, shoot Technical Pan film as an ISO of 6, develop in technidol developer (enlist advanced photo class people at a UNI to help with this). For color use Fuji Velvia at 50.
The photo class people will have the copy stands and appropriate cover glass / filters to get the contrast you want as well.
While I have not done maps, I have done large hand drawn artwork this way and the result is vastly better than you would get from directly shooting on a digital (IMHO).
Cheers,
-nB
whois gawk date unzip strip find touch finger mount join nice man top fsck grep eject more yes exit umount sleep dump
Stitching these together requires 0 effort in any modern photographic editing software.
I actually wrote a little piece of software to automate the stitching process. Just feed the script a bunch of scanned images and it'll align and stitch the images for you. Never got around to make a proper OSS project for it or advertise it, though.
It's here: http://mairas.net/wiki/Mapstitch