![]() When you’re figuring out a location’s coordinates on a paper map, you have a fair amount of work to do, aligning the location with primary tick marks and then adding and subtracting to get the exact coordinate. That’s where coordinate systems such as latitude and longitude and UTM come in. However, if you want to focus on a precise location on a map, you need a more sophisticated grid system. Letter-and-number coordinate systems are fine for highway maps, road atlases, and other simple maps where precise locations aren’t needed. Mathematician Rene Descartes devised this system in the 1600s. ![]() A location’s coordinates are expressed by drawing a straight line down to x and across to y. Most coordinate systems are based on x and y where x is a horizontal value, and y is a vertical value. For example, USGS topographic maps have latitude and longitude, Universal Transverse Mercator (UTM), and township and range marks. Often maps have multiple coordinate systems so you can pick one that meets your needs or that you’re comfortable using. You sank my battleship!"Ī grid may be printed on the map or provide tick marks (representing the grid boundaries) at the map’s margins. I call this the Battleship Grid System because it reminds me of the game where you call out coordinates to find your opponent’s hidden aircraft carriers, submarines, and destroyers. You now can say confidently that Biggs Junction is located at A12. Then put your finger on the city again, but this time move down until you reach the row of numbers. If you want to tell someone where the town of Biggs Junction is (for example), you put your finger on the city and then move it in a straight line to the left until you hit the row of letters. ![]() Grid systems are a whole lot easier to use and more accurate than "take the old dirt road by the oak tree for two miles, then turn left at the rusted tractor, and you’ll be there when the road stops getting bumpy."Ī simple coordinate system can consist of a vertical row of letters (A, B, C) on the left side of the map and a horizontal row of numbers (1, 2, 3) at the bottom of the map. A coordinate system is a way to locate places on a map, usually some type of grid laid over the map. ![]()
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