Historic Tromso

This cartographer added elevation data to an old map of his home in Tromsø, Norway, and the result is this gorgeous piece. twitter redit

I have a special interest in Tromso having been there and have collected remote sensing data there off and on.

See Webcam Sky Survey

I had trouble spotting Tromso on this map so I started comparing geography with google maps. Tromso is on an island which appears at the bottom left of the historic map and is cut off above Tromso. I will illustrate this using wiki's Map plugin.

Careful reading shows that this is the Ringvasoy quadrangle. I save as assets a slightly smaller map shown above and an excerpt of this showing the half of the island I do have.

I estimate the geographic bounds of interest and create a Map with this BOUNDARY. I estimate the extent of my excerpt and insert it with the OVERLAY option.

I can now pan and zoom the two maps together. I find geographic features that should align but don't. For two in corners I place markers on the feature and then another where it should be. I now should have enough information to align the two maps more closely.

When I decide I am going to tell this story here I decide to tighten up the view into my work before going further. I adjust the pan and zoom until I have a nice view and then place two more markers at the bottom left and top right of the desired view. I edit the Map markup and move these last to coordinates to refine the Boundary I made before.

I write an html script to perform this computation. I can see that this is going to require a lot of experimentation so I have the script fetch the original markup and show the improved markup in a Frame. github

Now copy-paste this computed markup into a new map.

I'm displacing overlay corners by deltas measured near but not at those corners. I'm also ignoring any rotation or projection differences which are even smaller errors.