So my friend Drew is writing another book.* The last time he did so he asked me to produce some maps for him, a process I detailed previously, and which we plan to repeat (roughly).* This time, Drew’s book is about an individual, who happens to have been born close to where I live.Being the kind of person he is, Drew has decided to set foot upon all the places most significant in his subject’s life.* Naturally, his birthplace fit’s into this category, so I applied myself to determining where, precisely, said event actually occurred.
Drew already had some pretty good ideas about this, having narrowed the search down not just to a small Massachusetts village but to a particular mountain within said village (coincidentally a mountain I had had occasion to map several years ago, so I already knew my way around rather well).
To narrow our search even further, Drew gave me a copy of a map he had found in a manuscript buried in the local library:
On the surface, it looked to be a workable map, so I converted it into a format I could work with and set about georeferencing it with QGIS.
The result was less than pleasing.* When it came down to it, I was not working with a map so much as I was trying to georeference a rough sketch.* With a capital “R”.* Under normal circumstances, this is where the process ends, and I simply produce a wildly inaccurate result with a pile of disclaimers attached to it.* But this was for an old friend, which is considerable coin.* Besides – I had some spare time with no pressing projects.
So I turned to one of my favorite mappers, Fredrick W. Beers.* There are Beers maps for everything within a sizeable radius of here and, being an archaeologist and historian, I have had to consult them on numerous occasions.* I can personally vouch for their accuracy whenever they depict objects that are still on (or under) the ground.
The mountain in question – Catamount Hill – is located in the town of Colrain Massachusetts, so I acquired the Beers map which includes said village and hill, which I then clipped to just the area of interest:
Unfortunately, the Beers map doesn’t show any of the landmarks that specifically interest Drew, but it does show a half dozen or so that are also on the aforementioned sketch map (the Stacy map), so I figured I could use the Beers map as a stepping stone.
The first order of business was to georeference the clip of the Beers map.* I have found that GIS software is only reasonably good at warping images, so I usually begin this process by helping them along with a little Photoshop chicanery.* As you can see, the Beers map shows a decent amount of local roads, and I have found through experience that most roads in New England haven’t moved much in centuries.* So I opened up QGIS and used a current local road shapefile to make a template image:
I then opened the template image in Photoshop, made the background transparent, and loaded the clipped Beers map underneath it.* Using Photoshop’s image transforming tools, I manipulated the Beers clip until it approximated the template image.* The result I saved for use in georeferencing:
Note that neither the Beers map nor the Stacy map had any real reason to use any sort of projection whatsoever, so I used Stateplane for the template (and for the rest of the georeferencing process, as well).
I then loaded the tweaked Beers map into QGIS and georeferenced it to the same road file I had used to make the template.* Once that was done, I created a point file of all the landmarks on the Beers map that I planned to use to georeference the Stacy map.* Then I added every other feature on the Beers map because I’m me.
I knew the roads on the Stacy map were out of kilter, so I decided to just ignore them altogether.* I loaded the map as an unprojected and unreferenced raster into QGIS and created a point file of all the features depicted on the map.* I named them all in a column in the table for use in labeling.* I then created a raster image of the labeled feature points, which I then georeferenced to the previously referenced Beers map, using the common features as control points.* I used this final, fairly accurate replica of the Stacy map to create a new point file of all the features in the Catamount Hill vicinity, numbered, typed and labeled in the table accordingly:
Finally – since I wanted to be able to use all of this to locate features on the ground – I reprojected everything and packed it into TileMill, which I used to create tiles for use with an app in my phone (similar to one I wrote about previously, only updated for use with a later OS).
Next week Drew and I plan to go out and put all this to the test.* Part of my plan is to locate a feature that intrigues me just because of its name:* Aunt Dinah’s Stairway.* I’m dying to know what it actually is.* Unfortunately, locating it will entail traveling to a place called Catamount Hill and hiking past landmarks called Bears’ Den and Black Snake Swamp.
Wish me luck.
Filed under: Friendship, GIS, Mapping Tagged: GIS, Mapping
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