Sunday, 13 March 2011
I mentioned a few weeks ago that I have a fondness for the old Bartholomew's 1/2" maps. It seems I am not alone. They haven't been published for over 30 years, so any we find in second-hand bookshops are hopelessly out of date. Even towards the end of their life they were beginning to get a reputation for being a bit unreliable. But back then apparently their fans were still so keen on them that they used to buy new Ordnance Survey maps so that they could transfer the details to their old Bartholomew's maps and continue to use them.
The obvious question is whether something similar could be produced today, using Open Street Map data. Naively I decided that I would try to find out, without really understanding what I was getting into.
There are some obvious differences between then and now. The basic design of the Bartholomew 1/2" dates back around a century, so they didn't have to cater for motorways. Road networks in towns are much more extensive these days than they were at that time. There have been changes in the type of information that is important now, compared to the information that was important then. They seem to label country estates, for example, and they used to mark Inns, but not Car Parks.
Apart from those changes, I've had to cope within my own limitations. I had created databases from OSM data before, so I know how to do that. I've become reasonably familiar with Postgis, and with some of the other tools that I needed. but I knew nothing about generating contour lines, and I hadn't used Mapnik until a week or so ago. There's a lot of useful information around, but it's been a steep learning process, and the old computer has been churning data for days on end.
I've made a start now, but there is still a lot that needs fixing. I haven't tried to get layers working yet, and I haven't put any labelling on the roads. Colours and icons could do with a lot of tuning, the scaling is only approximate (at 300dpi), it needs a legend, and copyright, and there's more detail to add. It only looks vaguely like the originals, and I'm not sure how much closer it can get.
Having said all that, I'm quite pleased with my first attempt. The basic mechanisms are up and running. I've learned a lot. Most of all, I've learned to respect the skills of the people who put the original Bartholomew's maps together at the end of the 19th century (and those who are putting together today's digital maps and tools).
There's a bigger example of how I am getting on, which covers a few square miles north-west of Maidenhead here. I've coloured the Motorways (blue), Trunk roads (green), Primary and Secondary roads (brown and yellow). Cycle routes are in Red, dashed if off-road, though I notice some are missing, which is something else to fix.
Posted by gom1 at 22:25