I’ve been trying to do something constructive at work today.
For those of you that don’t know, I work as a PA and office manager for my father-in-law who is one of the European gurus of GPS. Surveyors have little busts of him on top of their theodolites to which they occasionally make offerings of grain or small mammals.
In May, I’m accompanying him to a Navigation conference in Manchester. From what I understand, it’s going to be a big room with lots of very smart people who might want to buy things from us and I have to wear a suit. Being that this was my only understanding of my duties, PPD suggested that I try to learn a little about what we actually do. Not a bad suggestion, as it turns out.
So in my first act of trying to understand how GPS actually WORKS (I had a fair idea before, but some of my studies have been useful nonetheless) I’m going to attempt to explain the concept of triangulation to you, my readers. I would wager that 99.9 percent of you already KNOW what triangulation is, but my theory is, if I can explain it, I understand it.
Auntie Blogapotamus’s Triangulation Explanation (borrowed in part from howstuffworks.com)
Say that you’re lost. I mean, REALLY lost. Your plan to drive across country blindfolded wasn’t the best idea you ever had, and ever since the The Great Sign Blackout Bill passed under the Homeland Security Act, no place or street names exist any longer, but AT LEAST THE TERRORISTS DON’T KNOW WHERE THEY ARE EITHER, SO HA HA.
You stop to ask a passer-by where you are.
“You’re 625 miles from Boise.” says the terrified local, skittering for cover. The Great Sign Blackout Bill also made it a capital offence to TELL anyone their exact location. Let’s see those terrorists find any national monuments to blow up NOW!
Knowing that you are 625 miles from Boise isn’t much help. You could be anywhere within a 625 mile RADIUS around Boise.

So you see if you can scout out another local who might give you a better idea of where you are.
You finally find a guy on the corner and ask him.
“Well, I can tell you that you’re 690 miles from Minneapolis,” he says, taking a bite of his sandwich.
You drop him with a stomach punch. You’re starting to get very annoyed indeed. Knowing that you’re 690 miles from Minneapolis gives you a little more to go on, but still doesn’t really give you a good idea where you are.

Leaving your winded victim behind, you grumpily go in search of some real help.
The next person you encounter is a guy in a suit talking on the cell phone. He’s rather annoyed that you’ve interrupted his conversation with your trivial question.
“If you must know, you’re 615 miles from Tucson. Can’t you see I’m busy?” he snaps.
At which point you stab him in the face for being so unhelpful.
However, he has provided you with the last piece of the puzzle that you need to pinpoint your location.

You are in Denver. And you think you hear police sirens in the distance.
So, in theory, this is also how GPS works, albeit in 3 dimensions rather than two, with ellipses rather than circles and with 4 satellites instead of 3. (although you really only need 3 to get a fix) And with less stabbing.
Everyone clear?