This question is, like How long will it take to form a new dialect and language in underground steampunk London?, part of an experiment I'm conducting on Worldbuilding. I'm temporarily switching gears from linguistics to cartography, because an interesting issue has come up.
The setting so far is Victorian London - with a twist. Around the year 1850, massive coal deposits were discovered underneath central London (construction on the London Underground began roughly 15 years before it did in our world, and large-scale excavations started up quickly). Within five years, even larger seams had been found, and it became apparent that London was sitting on top of the largest coal seam discovered to that date.
By the year 1895 - the date of this story - the Underground project has expanded in conjunction with new mining enterprises, and there is effectively a second city underground, populated by workers and their families. I'm not entirely sure how deep it will run - certainly many hundreds and hundreds of feet - but it is quite sprawling.
I'd like to create a map of the city, both to present with any stories taking place there and to use for my own benefit when planning other things out. In a normal city, this would be simple. This city, however, is composed of a sprawling network of tunnels, caverns, holes and other structures, all placed at different depths underground, thanks to a lack of collaboration between mining companies in the early days of the boom.
How can I depict the whole city network in a two-dimensional map - with the technology available to a steampunk world (e.g. no computerized displays)?
I've read the following questions, but I think that they aren't quite sufficient.
- How can I indicate a third dimension on a map of outer space?: Rooms, caverns, city blocks and tunnels cannot be represented simply, like stars can. They are also all interconnected.
- Graphically represent (map) multiple spatial dimentions: This is close, but I'd like to not have to cut the map arbitrarily (or not so arbitrarily, e.g. at fixed depth intervals) because cuts could be straight through a large cavern, which would make for a disjointed map.
- Mapping a fantasy/horror building where rooms overlap: I need to actually represent the various structures inside; a circle will not suffice to designate a cavern.