A coordinate system is a way to locate places on a map, usually some type of grid laid over the map. 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.”
A 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. 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. Then put your finger on the city again, but this time move down until you reach the row of numbers. You now can say confidently that Biggs Junction is located at A12. 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. “B-3. You sank my battleship!”
A grid may be printed on the map or provide tick marks (representing the grid boundaries) at the map’s margins. Often maps have multiple coordinate systems so you can pick one that meets your needs or that you’re comfortable using. For example, USGS topographic maps have latitude and longitude, Universal Transverse Mercator (UTM), and township and range marks.
Most coordinate systems are based on x and y; where x is a horizontal value, and y is a vertical value. A location’s coordinates are expressed by drawing a straight line down to x and across to y. Mathematician René Descartes devised this system in the 1600s.
Letter-and-number coordinate systems are fine for highway maps, road atlases, and other simple maps where precise locations aren’t needed. However, if you want to focus on a precise location on a map, you need a more sophisticated grid system. That’s where coordinate systems such as latitude and longitude and UTM come in.
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. With digital maps on a computer, that’s usually just a matter of moving the cursor over a location and watching with relief as the coordinates automatically appear. If you’re using a paper map, you can make life easier with free overlay grids and rulers from www.maptools.com. With these, you can print grids and rulers for different coordinate systems on clear transparency sheets.
A 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. 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. Then put your finger on the city again, but this time move down until you reach the row of numbers. You now can say confidently that Biggs Junction is located at A12. 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. “B-3. You sank my battleship!”
A grid may be printed on the map or provide tick marks (representing the grid boundaries) at the map’s margins. Often maps have multiple coordinate systems so you can pick one that meets your needs or that you’re comfortable using. For example, USGS topographic maps have latitude and longitude, Universal Transverse Mercator (UTM), and township and range marks.
Most coordinate systems are based on x and y; where x is a horizontal value, and y is a vertical value. A location’s coordinates are expressed by drawing a straight line down to x and across to y. Mathematician René Descartes devised this system in the 1600s.
Letter-and-number coordinate systems are fine for highway maps, road atlases, and other simple maps where precise locations aren’t needed. However, if you want to focus on a precise location on a map, you need a more sophisticated grid system. That’s where coordinate systems such as latitude and longitude and UTM come in.
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. With digital maps on a computer, that’s usually just a matter of moving the cursor over a location and watching with relief as the coordinates automatically appear. If you’re using a paper map, you can make life easier with free overlay grids and rulers from www.maptools.com. With these, you can print grids and rulers for different coordinate systems on clear transparency sheets.
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