Map Coordinates - Most maps use a grid or coordinate system to find your location. This grid system is sometimes called a geographic coordinate system. The system defines your location by two numbers, latitude and longitude. Both numbers are angles that you make between your location, the center of the Earth, and a reference line.
Lines of latitude circle around the Earth. The equator is a line of latitude right in the middle of the Earth, which is the same distance from both the North and South Pole. In a grid, your latitude tells you how far you are north or south of the equator. Lines of longitude are circles that go around the Earth from pole to pole, like the sections of an orange. Lines of longitude start at the Prime Meridian, which is a circle that runs north to south and passes through Greenwich, England.
Longitude tells you how far east or west you are from the Prime Meridian. You can remember latitude and longitude by doing jumping jacks. When your hands are above your head and your feet are together, say longitude (your body is long!), then when you put your arms out to the side horizontally, say latitude (your head and arms make a cross, like the “t” is latitude). While you are jumping, your arms are going the same way as each of these grid lines; horizontal for latitude and vertical for longitude.
If you know the latitude and longitude for a particular place, you can find it on a map. Simply place one finger on the latitude on the vertical axis of the map. Place your other finger on the longitude along the horizontal axis of the map. Move your fingers along the latitude and longitude lines until they meet. For example, if the place you want to find is at 30oN and 90oW, place your right finger along 30oN at the right of the map. Place your left finger along the bottom at 90oW. Move them along the lines until they meet.
Your location should be near New Orleans, Louisiana along the Gulf coast of the United States. Also, if you know where you are on a map, you can reverse the process to find your latitude and longitude. One other type of coordinate system that you can use to go from one place to another is a polar coordinate system. Here your location is marked by an angle and distance from some reference point.
The angle is usually the angle between your location, the reference point, and a line pointing north. The other number is a distance in meters or kilometers. To find your location or move from place to place, you need a map, a compass, and some way to measure your distance, such as a range finder. Suppose you need to go from your location to a marker that is 20oE and 500 m from your current position. You must do the following:
- Use the compass and compass rose on the map to orient your map with North.
- Use the compass to find which direction is 20oE.
- Walk 500 meters in that direction to reach your destination.
Polar coordinates are used most often in a sport called orienteering. Here, you use a compass and a map to find your way through a course across wilderness terrain. You move across the terrain to various checkpoints along the course. You win by completing the course to the finish line in the fastest time.
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