Monday, February 03, 2020

Bushcraft Map Making Meets JavaSript Hacking

Let's say you wanted map a relatively large area (a few miles square) and had no GPS. How could you create a scale sketch of the area using nothing but a compass, ruler, notebook, pencil and string?

One answer, as this Coalcracker Bushcraft video suggests, is to use a mapping technique referred to as PAUL Mapping. While I wasn't able to figure out what the acronym PAUL stands for, I have to admit the approach is clever. The quick version is this: you record the heading and pace count to notable points in the area. For example:

120°, 80, Stream Crossing
240°, 43, Double Oak
65°, 120, Cabin
280°, 30, Spring

In the above data, I'm suggesting that 'Stream Crossing' is 80 paces, on a bearing of 120°, from an arbitrary start point. The 'Double Oak' is 43 paces, on a bearing of 240°, from the 'Stream Crossing' and so on.

While I imagined collecting up this data was useful, it wasn't obvious to me how this could be turned into a field expedient map. The video goes on to explain: you install a wooden peg and call that your start point. You then use a ruler to measure out a proportional amount of string. Say, 1 inch is 10 paces. To mark off 80 paces you'd unspool a piece of string 8 inches long. Using your compass as a protractor, and string as a measuring device, you can you install the "Stream Crossing" peg 120° and 8 inches from the first peg. You then repeat the process till all points are plotted.

While the explanation is long winded, the technique is straightforward. And when you're done, you have a string and peg scaled map of the area. Want more information on your map? Measure off more points and add them to the map. Because the map is to scale it's possible to make navigation and other assumptions from it.

To experiment with this technique, I wrote some code that turns the logged data into an on screen drawing. You can feed the above chart of information into my PAUL Mapping demo and see the following output:

This was a humbling project. I expected I could turn it out in no time, but got tripped up by the nuances of the HTML canvas and the need to transform points for the various coordinate systems. As it stands, it's still buggy and not rendering the data right. Though I have confidence I'll get this figured out.

Once I get it working, I'll have to try my hand at some local map making.

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