QGIS

I’m going to describe how I imported an 1899 map into WikiMapping.  Why do this?  It’s searchable.  I can trace it and bring the data into my own maps.  I can highlight information to share with others.  And, I just love old transit maps.

The project I’m referring to is here.

Mike Szilagyi had given me a scan of some Philadelphia trolley maps, and I don’t know if I ever put them on PhillyMap.com.  Since I came across them, I thought I might put a hundred and fifteen year-old map on WikiMapping.

In QGIS, there is a georeferencing plug-in.  I followed the steps in the Kindle book, Learning QGIS 2.0, which is pretty basic but still useful.  I don’t think one needs much guidance.  You have to load an open street map or other base as a reference. The general concept is to open an unprojected tif, click a point on the tif, and then click a point on a corresponding reference base map in Web Mercator.

There were a couple of good tips for saving the document.  I used the following.

• Create, and save a ground control points file
• Tranformation: polynomial algorithm 2 (from the pull-down menu).  I could have used 3, but 2 was sufficient.
• Resampling method: Cubic
• There’s an option to load the reprojected image into your project.

From here, you can create map tiles using a plugin called QTiles.  If you are going to host your files on your own server, then you can use a larger zoom level.  The file size limit on WikiMapping is 100 MB.  For this map, I could get to a zoom of 15.  A zoom of 18 was nearly a gigabyte in size.

Saving all of the levels took about 15 minutes on my Macbook Air.  Speaking of which, my old laptop is powerful enough so that I can work on a 350 MB map, about 80MB of which is raster and MAPublisher data.

To sum up… I feel confident that I can get any map that I need to into WikiMapping.  And by placing a destination point, I can get directions to that point and see my current location on the old map.  It’s a fun way to explore history.