#googlemap mashup

[maple-clef]

EDIT 9/2/15: Taken offline for now (for the reasons below). Hope anyone who wanted a look had the chance! And let me know if you want more info on the "how to" side of things.

Okay, so I did a Thing with Stephen Walter's new map of the Rivers of London. I georeferenced it and created a scalable, transparent overlay for Google Maps, so you can zoom about and change transparency (with the volume slider-like thingy, top right) and see how the rivers (particularly the hidden ones!) relate to modern day London.

I've uploaded it so that people can have a look, but I won't leave it up for very long because I'd really want to get permission from the artist. This was mostly to create something I could play about with offline - if it were to go up "properly", I'd create additional layers or pins with points of interest from the books (I think I might have seen something similar on BA's blog).

Ultimately, it could form part of a great splash page for a site with info tagged to the map - you can even geotag wordpress posts and generate pins on the map using the metadata, although it requires a bit of hacking of the php.

But yes, if you're curious, have a look - I'll leave it up over the weekend.

And if you wanted to recreate it yourself, you'll need:

MapTiler (there's a free version if you don't mind a watermark)

the high-res version of the map image

A bit of time to play around

Start MapTiler, and add in your image. You want to create Mercator Tiles (not a Google Earth overlay). Then georeference (add ground control points in areas common to both the picture and the reference map), the more the better (I used 20), the more evenly spread the better. Then save, choose a zoom range (say, 10 to 14), save to folder, and click 'Render'. You'll be asked to create a folder somewhere to save everything to.

Maptiler creates 3 different versions of the page, but the index.html one will give you the transparency tool and bog standard Google Maps hybrid baselayer.

Let me know if you have any questions about the process :)