# topographic maps what do topographic maps do?!? in contrast to most maps, a topographic map shows...

Post on 13-Dec-2015

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Slide 2 TOPOGRAPHIC MAPS Slide 3 What do topographic maps DO?!? In contrast to most maps, a topographic map shows the shape of the Earths 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 Slide 4 Slide 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! Slide 6 SEA LEVEL Slide 7 RISING WATER Slide 8 Contour Lines Slide 9 CONTOUR MAP Slide 10 Steepness Slide 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!! Slide 12 Slide 13 Map Scale Ratio of the distance on the map to the distance on the ground 1.Graphic: Slide 14 Map Scale 2.Verbal: 1 inch equals 10 miles Slide 15 Map scale 3.Representative fraction or ratio: 1:24,000 Units dont matter Slide 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? Slide 17 .E.E What is the highest possible elevation for point E?!? Slide 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 Slide 19 The value of the first hachured line REPEATS the value of the last normal line! Slide 20 A 3-D View of a Depression Slide 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!! Slide 22 RIVERS Slide 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! Slide 24 Towards which compass direction is the Green River flowing? It is flowing towards the NW! Slide 25 What about these?

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