Sunday, November 10, 2013

Using a Compass to Find Treasure

Back in February, we said one of the things we wanted to get better at was navigating by compass.  A common exercise for aspiring orienteers is practicing in a familiar area such as one's backyard.  As it just so happens, a treasure map showed up in our mailbox this week.  It even has a north arrow and scale bar!  What a considerate cartographer!  Let's follow it and see what we find!

It looks like a map of our yard, amateurishly constructed in PowerPoint! Somewhat disconcerting, but it seems to suggest we need to start at the mailbox, get a shovel from the garage, detour to the biggest tree in the yard, and then head toward the second-biggest tree at the northwest corner of the property.  The treasure is just southeast of that tree.  What's the best way to follow the dashed line?  Since we're trying to get compass practice, let's use a compass.
Assume that we don't know right where on the map we are to start with.  As it happens here, we can see two landmarks, which means we can triangulate our position.  If we hold the compass in front of us and face the northeast corner of the house, we see that we are standing along the 330° bearing line.  If we face the southeast corner of the house (actually the carport), the compass tells us we're on a bearing of 250°.  Where those two lines intersect is where we are.  If we wanted to, and also had a ruler, pencil, and calculator with trigonometric functions (or sine/cosine/tangent tables) handy, we could draw those lines on the map.  Or, we could approximate with grid lines on the map or by holding the compass by the map.  In any case, it looks like we're standing at the mailbox.  Thank goodness!  If things go badly, we can probably find our way home from here.
In the current scenario, we can see through the carport to the southwest corner of the house, which is where the black dashed line on the map almost intersects the house.  If we use the compass to get a bearing between our current position and the southwest corner of the house, we should be able to walk along that line to the point where we can peek around the corner and see the garage.  It's trivial here, but if that corner was half a mile away and we had to go through dense woods or fog on the way and lose sight of the landmark, the compass would be a lot more helpful.  Sorry the numbers on our little compass are hard to see--but the red North direction is visible, and the other large lines correspond to 90° increments.  The small lines (if you can see them) are 10° increments, and every 30° increment is labeled with text.
Garage ho!  Shovel ho!  [Insert music for video game character finding useful tool here.]
Now we need to head due west to the edge of the shed, at which point we can turn and head toward the big tree along the dashed black line.
Compass says the first tree is on a bearing of 330° from the southwest corner of the shed.  What a magnificent tree.  It must be a tree from heaven.  Actually, it is a tree of heaven, an invasive species imported from China.  Fun fact: the bruised leaves smell vaguely like peanut butter.  Don't eat them.  Katie says, "We can also see the tree next to the 'X' on the map.  Why don't we just walk there?"  Because the map says we have to go by the big tree, Katie!  Who knows?  There might be bandits or crocodiles along the direct route.
It's sometimes a good idea to get high up in the air and survey one's surroundings to find landmarks and regain one's bearings.  Katie says, "The landmark you're looking for is 20 yards away and you can probably see it better from down here where there aren't any branches to block your view."  Compass says we need a bearing of 275° to find the next tree.
There's the X!  It's not red like the map shows, but this must be it.  Time to start digging!
A hastily-constructed wooden trunk buried in a shallow hole!  How mysterious!  Whoever buried this treasure must have been worried about getting caught.
Hey!  The treasure is Katie's cell phone!  It must have been there for hundreds of years.  Katie says, "I can't believe you went to the trouble of making a wooden trunk out of pallet wood, hiding my phone in it, and burying it in the yard just to get some practice with your compass."

If this practice exercise didn't make sense, check out a real orienteerer's guide with a different kind of compass.  For more advanced exploring, there are other things to think about, like the difference between true north and magnetic north and the inherent uncertainty in getting and following a bearing (especially with a little compass like ours!), but for now, we at least know how to find buried phones in the backyard.

What kind of buried treasure have you found in your yard?  What was a situation where you really needed your compass?  Let us know in the comments section below!


  1. I'm cry-laughing right now. Katie is a very patient woman!

    1. Fortunately she didn't have any missed calls while it was buried. :-)