2. TOPOGRAPHIC MAPS

3. What do topographic maps DO?!? In contrast to most maps, a topographic map shows the shape of the Earth’s surface by using contour lines. Contour Line - a special type of isoline that connects points of equal elevation (distance above sea level) on a topographic map

5.  The United States government prints topographic maps for every square INCH of our country.  It is conducted by the USGS (US Geological Survey)  They have been doing this since 1897!!  They update individual maps in a timely manner.  There are 54,000 individual maps to cover the entire United States.  They are called “quadrangles” - probably because they are quadrilaterals!

6. SEA LEVEL

7. RISING WATER

8. Contour Lines

9. CONTOUR MAP

10. Steepness

11. contour interval map scale ALWAYS the first things that you must determine when looking at a topographic map are the contour interval and the map scale! WHY?! You just might be asked to calculate the gradient! DUH!!

13. Map Scale Ratio of the distance on the map to the distance on the ground 1.Graphic:

14. Map Scale 2.Verbal: “1 inch equals 10 miles”

15. Map scale 3.Representative fraction or ratio: 1:24,000 Units don’t matter

16. SPECIFICS!! 1) The top of a hill may not be exactly the same as a contour line. Therefore, you may need to say what the “highest possible” elevation is: The elevation at point “D” is higher than 160 feet above sea level, because it is inside the 160 ft contour line. So what is the HIGHEST it can possibly be?

17. .E.E What is the highest possible elevation for point E?!?

18. Hachured Lines  A “hachured line is a “hairy line” which shows a hole in the ground.  DEPRESSION - a hole in the ground  There are special rules that apply in this situation

19. The value of the first hachured line REPEATS the value of the last “normal” line!

20. A 3-D View of a Depression

21. 2) Finding the LOWEST possible elevation at the bottom of a depression: What is the lowest possible elevation at the bottom of this depression? 61 feet!!

22. RIVERS

23.  To figure out the direction a river is flowing, you look at the “bends” in the contour lines that cross over the river.  The “blip” points UPstream (where the water comes from).  The water flows DOWNstream!

24. Towards which compass direction is the Green River flowing? It is flowing towards the NW!

25. What about these?