THIS CHAPTER
Back in 1992, a cargo ship lost a container and launched almost 29,000 bath toys into the northern Pacific Ocean. Plastic beavers, frogs, turtles, and ducks, all bobbing along, wave after wave. Dubbed “the Friendly Floatees,” these plastic toys — cute as they were — added to a growing ocean pollution problem. But they had one useful benefit, and that was to help model ocean currents.
As the toys washed ashore or were seen at sea, a very useful piece of information was collected: their location. To relay that information to others, humans have devised a number of ways to express location on Earth’s surface. In this case, the ducks and their friends were identified using latitude and longitude, a set of invisible lines and coordinates that describe where things are.
But how does this imaginary system work? Let’s visit Gridville to find out.
Welcome to Gridville
Welcome to Gridville, the cute little burg shown in Figure 3-1. You and I are going to pay this town a quick visit because it looks like a great locale to review basic concepts of location (latitude and longitude), the topic of this chapter. I say “review” because if you are like most people, then you probably learned about these things during elementary or middle school, but may have forgotten some or most of it later on.
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FIGURE 3-1: A map of Gridville.
Knowledge of latitude and longitude gives you basic location and orientation skills regarding our planet Earth. It also affords the opportunity to learn all sorts of little tidbits, which, in addition to impressing your friends, can greatly enhance your understanding of geography.
Feeling Kind of Square
To get started, look at Figure 3-1 and familiarize yourself with Gridville. In particular, note the following:
The roads are aligned with the cardinal directions — that is, they run north-south or east-west. The result is a grid pattern of north-south roads that intersect east-west roads at right angles. So, getting right with Gridville means getting used to a city that is all right angles and nothing but right angles. Thus, I’ll understand if this town leaves you feeling a little square.
North is toward the top of the map; south is toward the bottom; east is toward the right; and west is toward the left. This is a near-universal rule in map-making, but you should always carefully examine the map you are looking at and confirm which way is which.
Gridville has a principal east-west road named Equator Boulevard, and a principal north-south road named Prime Meridian Way. The two roads cross in the middle of Gridville.
Every other road in Gridville has a name that refers to its location relative to those two roads. Thus, streets are numbered consecutively north and south of Equator Boulevard. Avenues are numbered consecutively east and west of Prime Meridian Way.
A big dot and a letter mark two intersections. I’ll refer to these shortly.
Telling Someone Where to Go
Because geography involves locations and directions, it affords ample opportunity to tell someone where to go. Suppose you live in Gridville and are standing on the sidewalk at Point A, the corner of North 4th Street and East 3rd Avenue. A stranger from out of town comes up to you and asks for directions to Gridville Hospital — can you help her?
Of course, you can. You know the hospital is located at Point B on the map. And you can convey that information to the stranger by stating either the hospital’s relative location or absolute location.
Relative location
In the first instance, you can tell the stranger how to get to the hospital from Point A. For example (pointing west along North 4th Street), “Go that way four blocks, turn left, and walk five more blocks.” This is called relative location because the information you gave is relative to Point A. Give those directions verbatim to the stranger at any other intersection in Gridville, and the result is a lost stranger.
Absolute location
As an alternative, you can convey the location of the hospital with respect to its grid coordinates — that is, its location within the grid system. For example, “Go to the corner of South 1st Street and West 1st Avenue.” This is called absolute location because theoretically, those directions work anywhere in Gridville, not just at Point A.
The best location to use
Both relative location and absolute location have the potential of getting the stranger to the desired destination. And chances are you have used both types of location to direct someone to a destination in your town, neighborhood, or environs.
The Global Grid: Hip, Hip, Hipparchus!
As chief librarian at the great library in Alexandria, Egypt, Hipparchus compiled information
