Saturday, April 12, 2008

Tell Direction With Your Cell Phone and the Sun

By Matt:

There are a number of articles available with tips on how to orient yourself out in the wild. You can put a stick in the ground and watch the shadow's movement for thirty minutes, and you can even use an analog watch to create a makeshift compass.

But here's the thing - when I'm on a business trip driving in an unfamiliar place, and I'm late for a meeting, I don't have time to pull over and put a stick in the ground. In spite of that, I can quickly orient myself and get a general sense of direction using nothing but the clock on my cell phone. Here's how...

These are a few simple guidelines to keep in mind for our Northern hemisphere readers:
  • At 12:00 Noon the sun is directly South
  • At 6:00 AM the sun is directly East (even if it hasn't risen yet)
  • At 6:00 PM the sun is directly West (even if it has already set)
  • Facing the sun before Noon means you are looking between East and due South
  • Facing the sun after Noon means you are looking between due South and West
Based on these rules I can estimate the four cardinal directions - North, South, East, and West - and quickly be on my way:
  • For instance, if my cellphone says it is 9:00 AM the sun is going to be halfway between East and South (or Southeast). Approximate South by visualizing a 90-degree angle with the left line pointing towards the sun, and bisect the 90-degree angle to arrive at South.
  • If it's 3:00 PM, the sun is halfway between South and West (or Southwest). Again visualize a 90-degree angle, this time with the right line pointing towards the sun, and bisect the 90-degree angle to arrive at South.
  • Basic geometry can help you find South at other odd times. At 2:15 PM, use the same 90-degree angle process as the 3:00 PM example above, but this time adjust for the fact that it's earlier in the day. Bisect the angle again, but this time South will be slightly farther to your right (not more than 15-degrees, as the sun moves across the horizon at 15-degrees per hour).
Disclaimers And In Practice
Now it is important to remember is that these are approximations, and just a basic way to get a general sense of direction. Our Southern hemisphere readers will have to remember that at Noon the sun is directly North, not South, and the tips above will need to be reversed to account for this. Also, the guidelines are further complicated by Daylight Savings Time - which will shift your results by 15-degrees - but again, these are just basic orientation tricks.

With some practice you'll be able to glance at your phone, and glance at the sun, and determine your direction within a matter of seconds. So if you're driving along the Interstate and your hotel is located North of downtown, but it's Noon and you're driving away from downtown with the sun blazing through your windshield, then you're traveling the wrong way!

I hope these tips will aid to ease your mind during your next "I'M LOST!" panic attack... let us know how it goes!


Michael Henreckson said...

My suggestion: try a GPS unit. A little bit pricier but much more effective because you have an overview of the roads around you. It also always knows where you are. To be sure there are times when you would pick different roads than the GPS would, but if you use it to get the big picture it can be very helpful.

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