TOPOGRAPHIC MAPS Lesson 6

INTRODUCTION-GEOCACHING

In May of 2000, people started playing a new version of the game of hide-and-seek using GPS (Global Positioning System) to precisely locate any place-or thing. People started hiding objects in the woods or mountains, and then used GPS data to post these locations on the Internet. They challenged other people to find the objects, and the sport of geocaching was born! With GPS technology nothing is hidden long, but searchers still might need to use maps for their quest. A cache can be found anywhere, so people searching for the cache need to rely on topographic maps.

WHAT IS GEOCACHING? LET’S WATCH A VIDEO https://www.youtube.com/watch?v=bQgP3XPZwPs

HOW TO MAKE A GEOCACHE https://www.youtube.com/watch?v=qq1zlIDdXrg

VOCABULARY 1.) topographic map-a map showing the surface features of an area

2.) contour line-connects points of equal elevation

3.) contour interval-the change in elevation from one contour line to the next

4.) index contour- every fifth contour line; these lines are darker and heavier than the others

5.) geocaching-geo means earth, cache means storage

HOW DO MAPS SHOW TOPOGRAPHY?

Topographic maps show the land as if you were looking down on it from above. They provide accurate information on the elevation, relief, and slope on the ground.

READING CONTOUR LINES Mapmakers use contour lines to show elevation, relief, and slope on topographic maps. Contour lines connect points to equal elevation. In the USA, most topographic maps give contour intervals in feet rather than meters.

The change in elevation from one contour line to the other is called the contour interval. The contour interval for a given map is always the same. For example, this map has a contour interval of 160 feet. If you start at one contour line and count up 10 contour lines, you have reached an elevation of 1,600 feet higher. Every fifth contour line is known as an index contour line. These lines are darker and heavier than he others.

CONTOUR LINES

KEYContour interval 160 feet

INDEX CONTOUR LINE

READING A TOPOGRAPHIC MAP Looking at a topographic map with so many squiggles, you may feel as if you are gazing into a bowl of spaghetti, but with practice you can learn to read a topographic map. First, you must become familiar with the map’s scale and interpret the map’s contour lines. Many topographic maps are drawn at a scale of 1:24,000, or 1 centimeter equals 0.24 kilometers. At this scale, maps can show features such as rivers and coastlines. Large buildings, airports, and major highways appear as outlines. Symbols are used to show houses and small features.

To find the elevation of a feature, begin at the labeled index contour, which is a heavier line than regular contour lines. Then, count the number of contour lines up or down the feature.

Reading contour lines is the first step toward “seeing” an area’s topography. Look at the topographic map, the closely spaced contour lines indicate slopes or relatively flat areas. A contour line that forms a closed loop with no other contour lines inside indicates a hilltop. A closed loop with dashes inside indicates a depression, or hollow in the ground.

The shape of contour lines also helps to show ridges and valleys. V-shaped contour lines pointing downhill indicate a ridge line. V-shaped contour lines pointing uphill indicate a valley. A stream in the valley flows toward the open end of the V.

ASSESS 1.) What technological advance made the sport of geocaching possible?

2.) What is the difference between an index contour and a regular contour line?

3.) How do you identify the index contour lines on a map?

4.) How can you determine the contour interval on a topographic map?

5.) What information does a topographic map provide that a regular map does not?

6.) What features on a road map are also on a topographic map?

7.) How does a topographic map serve as a good model of a mountain? What is it missing?

8.) On a topographic map, how would you show an island in the ocean with an elevation of 80 feet if the contour interval is 10 feet?

9.) You see that a topographic map of your area has a scale of 1: 24,000. What does this tell you?

10.) On topographic maps, what three things do mapmakers use contour lines to represent?