Mapping Hacks

207

Chapter 5

CHAPTER FIVE

Mapping with Gadgets

Hacks 47–63

You got to be careful if you don’t know where

you’re going, because you might not get there.

—Yogi Berra

We like to know where we are! We’re fascinated with location and what

location says about narratives and journeys. One of the earliest written

works in the Western tradition is The Odyssey, recounting brave Odysseus’s

journey home from Troy, and his problems with (the wrong!) location. The

rise of affordable personal GPS units has given a huge boost to our interest

in place, in maps, and in narratives of place. GPS units allow us to docu-

ment the journey of our own lives with specific times and locations.

How GPS Works

The Global Positioning System, or GPS for short, is a marvel of modern

technology. The 24 NAVSTAR satellites that make up the orbital compo-

nent of the Global Positioning System were launched by the U.S. Air Force,

starting in 1978. The satellites orbit Earth about 650 kilometers above its

surface and are staggered in such a way that three or four should be over-

head, anywhere on Earth, at any time. Each satellite carries an atomic clock

on board, which it uses to transmit the precise time over a microwave signal

back to receivers on Earth, along with a set of 3-D position data, called an

ephemeris, which describes the satellite’s location in the sky.

According to Einstein’s Special Theory of Relativity, a radio signal