The common scale for these maps is 1:600. For example, township engineers generally need extremely detailed maps that show sewers, power and water lines, and streets. The scale corresponds to its intended use. However, you can find maps of various areas at all different scales. It requires about 57,000 maps at this scale to cover the 48 contiguous United States, Hawaii and territories. You may also see footbridges and private roads on a map of this scale. The more populated areas of Alaska, though, map at the typical 1:24,000 or 1:25,000.Ī 1:24,000 map is large and provides a lot of detail about the area - it will include buildings, campgrounds, ski lifts, among other things. A couple of states map at 1:25,000, and most of Alaska (due to its size) maps at 1:63,360. Puerto Rico, for example, maps at 1:20,000 or 1:30,000 because the country originally mapped at a metric scale. You'll find most of the United States mapped at the 1:24,000 scale, with only a few exceptions. Maps based on metric units use a scale of 1:25,000, where one centimeter equals 0.25 kilometers. Look in the margin of your map to find out its contour interval.įor USGS topographic maps, 1:24,000 is the scale most often used. This makes it easier to read the map - too many contour lines would be difficult to work with. If, for example, the general terrain is quite elevated, the map might run at 80- to even 100-foot (24- to 30-meter) intervals. Different maps use different intervals, depending on the topography. For example, if your map uses a 10-foot contour interval, you will see contour lines for every 10 feet (3 meters) of elevation - lines at 0, 10, 20, 30, 40 and so on. We call this spacing the contour interval. In order to keep things simple, topographic maps show lines for certain elevations only. The line you see will look like a contour line on a topographic map. Here's a cool way to understand how to interpret contour lines: Take an object like a ball or a pile of laundry, and shine a red laser pointer along the object's side. They're useful because they illustrate the shape of the land surface - its topography - on the map. Contour lines show elevation and the shape of the terrain. Contour lines are lines drawn on a map connecting points of equal elevation, meaning if you physically followed a contour line, elevation would remain constant. © HowStuffWorksĬontour lines are the greatest distinguishing feature of a topographic map. Geological Survey (USGS) lists the following symbols on its topographic maps:Ĭontour lines help users to see points of equal elevation. Each color means something different.Ī topographic map uses symbols to keep the map less crowded, but it's still chock-full of information. You'll see these lines in many colors - brown, blue, red, black and purple. These lines indicate boundaries, contours, roads, streams and more. Lines on a topographic map can be straight or curved, solid or dashed, or a combination. You'll see big buildings - your local shopping center, for example - as their actual shapes. On these maps, you'll see large expanses of green for vegetation, blue for water and gray or red for densely built up areas. The first step in learning how to read a topographic map is to understand how to interpret the lines, colors and symbols. People use topographic maps for engineering, conservation, environmental management, public works design, urban planning and outdoor activities like fishing, hiking or camping. The advent of airplanes in the 1940s helped to advance mapping techniques.īecause the maps show so much information, they have a wide variety of uses. Then they would plot their maps, with the features that they could see and measure. Mapmakers would find an area's best vantage point - usually the highest point - and climb up to it with drawing boards and sighting devices. Mule pack train was the only way to reach the mostly unsettled West, and cartographer's tools were crude compared with today's. When the USGS first started creating maps - which it did to catalog public land - the process was time-consuming and costly. Developments in aerial photography and satellite imaging make these maps much more accurate and efficient to produce than in the days when they were created by hand. Geological Survey (USGS) produced its first topographic map in 1879, and it still produces them today. This contour and elevation information distinguishes them from other maps. These maps show the land's contours, elevations, mountains, valleys, bodies of water, vegetation and more. What's the difference between a topographic map and a regular map? In a nutshell, topographic maps allow you to see a three-dimensional landscape on a two-dimensional surface.
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