Area Mapping On Foot

[Jinumon]

Hey all,

Coupled with my discussion of overland speculative trade a few weeks (months?) ago, I've been brainstorming a system for running "hexcrawls" in GURPS.

First of all, huge shout out to Bill Stoddard and Sean Punch for their previous advice and work on DF16 - Wilderness Adventures, respectively. They've been an immense help! On to the actual topic.

From DF16 - Wilderness Adventures, p. 27: "Conquerors and delvers prize area maps. Creating these on foot means zigzagging across a region for longer than is fun for most players."

My question here is, assuming you did have players interested in this, especially as it relates to long-running campaigns, how long would it take?

I should note that I realize the answer to this question is infinitely variable depending on the specifics of terrain; my primary goal here is coming up with something that is reasonable, gameable, and that is preferably more grounded than "as long as you want it to take." What follows is some of my own musings on the topic. I am not an expert on this topic so consider this sentence as one big qualifier for what follows. Feedback and advice is welcome and encouraged.

The smallest scale for area maps seems to be about 1:5,000, wherein one inch on a map corresponds to 5,000 inches, or about 420 feet. Assuming we want a map that is accurate enough to distinguish, say, individual units in a tenement building, we'll probably want it accurate to around 10 feet. That's the modern equivalent of 42 dpi, or about 1,800 data points per square inch.

Jane Cartographer has Cartography-12 and Observation-12. She stands between 5 and 6 feet tall and can see about 3 miles on "flat" ground before the horizon makes further observation impossible. As she walks, she observes a swath of land to her left and right and sketches on a hardback she carries with her.

Jane is unhurried and unthreatened (+4), and while the terrain isn't as obvious as an oncoming car (+10, p. B358), it is stationary and in plain sight (+8). Desiring a map accurate to about 10 feet, she only takes note of the terrain in 3-yard patches (SM+1). Assuming she takes no penalty for darkness or weather, her effective skill is 25.

Jane wants her map to be as accurate as possible. Considering a roll of 17+ is always a failure, she can take up to a -9 and still have an effective skill of 16. The distance at which Jane suffers a -9 penalty on Vision rolls is 100 yards, meaning she can map a swath of land 200 yards wide as she travels. For every mile Jane walks she maps an area of equal to ~0.11 square miles (600/5,280). Assuming she occasionally backtracks or crosses her own previous path, let's say 0.1 square miles.

Conclusion: the base rate at which one can map an area of the Plains terrain type, in square miles, is equal to (linear miles traveled/10).

I really hope I'm not totally off-base with this. Please let me know what ya'll think. Ya'll are the best!

Jinumon