How to read a topographical map Unit 3: How to read a topographical map

What is a topographic map? Shows the shape of the Earth’s surface Contour lines … imaginary lines that show heights, depths, and steepness The distinctive characteristic of a topographic map is that the shape of the Earth's surface is shown by contour lines. These imaginary lines allow you to see the height of mountains, depths of the ocean bottom, and steepness of slopes. In the United States, the U.S. Geological Survey (USGS) is responsible for topographic mapping.

Features on a topographic map What features do you notice on this map? Topographic maps use a wide variety of symbols to represent human and physical features. The first features usually noticed on a topographic map are the area features, such as vegetation (green), water (blue), and densely built-up areas (gray or red). Topographic contours are shown in brown by lines of different widths. Each contour is a line of equal elevation; therefore, contours never cross. Contours that are very close together represent steep slopes. Widely spaced contours or an absence of contours means that the ground slope is relatively level. In densely built-up areas, most individual buildings are omitted and an area tint is shown. On some maps, post offices, churches, city halls, and other landmark buildings are shown within the tinted area.

Examples (Beaufort, NC) (Yosemite National Park, California) Here are a few examples of various topographical maps from around the country. Does anything stand out to you as far as the similarities or differences between them? What about how the map looks relative to its location? (Salt Lake City, Utah) (Mount Rainier, Washington)

Summary! Thin brown lines represent contours or points of similar elevation. The closer together they are, the steeper the terrain. Contour lines form "v" shapes in valleys or along stream beds. The point of the "v" points uphill. Blue represents water. Green represents orchards and forested areas. Purple markings are those that have been "photorevised," or added to the map since the original map was published. Red areas represent urban areas, although the maps will often indicate special buildings of significance within the urbanized area. Roads and highways are represented in black and red.

Practice! Can you locate: A river? A reservoir? A valley? A mountain peak? <Instructor: have students locate these items on the map using the Elluminate drawing tools. They can circle or write their initials or label the map in any way that works for you and them. Encourage participation and discussion about how students are locating these things on the map.>

Topographical Map of U.S. Do you notice how mountain ranges and major water ways stand out so clearly on this topographical map of the United States? Can you identify the Rocky Mountains? Can you identify the Mississippi River? Can you find the Great Plains? How about the Central Valley? <instructor: have students identify these places or others on the map using the Elluminate drawing tools. They can simply circle locations on the map or use initials or dots.>