How are Maps Made?

1. How are Maps Made? • Aerial photographs provide much of the data used for mapmaking. • Cameras mounted in planes take photographs as strips of Earth’s surface. • The strips are put together like a puzzle to create an image of a large area. • Two aerial photographs of the same area, taken from different angles, are used to create a three-dimensional image. 1. Explain How are aerial photographs made? (contd.)

2. How are Maps Made? • Satellite images are also used to make maps. • Mapping satellites use electronic devices to collect data about the land surface. • Computers use the satellite data to make images. The images are made of pixels, each of which contains information about the color and brightness of a part of Earth’s surface. • Earth’s surface is shown in different colors, depending on the ground cover. Vegetation are often shown as red or green, water as black or blue, and cities as bluish-gray. 2. Describe What would the area around your school look like on a satellite image?

4. How do Maps Show Topography? • A topographic map shows the three dimensional features of an area. • A contour line is a line that connects points of equal elevation. • A contour interval is the change in elevation from one contour line to the next. It is always the same for a given map. 3. Define What is a contour line? (contd.)

5. How do Maps Show Topography? • Thin brown lines represent contours. • Closely spaced contour lines indicate steep slopes. • Widely spaced contour lines indicate gentle slopes or relatively flat areas. • A contour line that forms a closed loop with no other contour lines inside indicates a hilltop. • Contour lines form “V” shapes in streams. The closed end of the “V” points upstream. 4. Explain What would the contour lines look like for a canyon?