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Topographic Maps Wednesday, January 25, 2012 What is a topographic map? A map that shows elevation changes for a specific region. PURPOSE OF A TOPO MAP A MAP PROVIDES INFORMATION ON THE EXSISTENCE OF, THE LOCATION OF, AND THE DISTANCES BETWEEN GROUND FEATURES. Contour Lines Contour lines indicate elevation. They are the main part of any topographic map. Regular Contour Lines Regular contour lines are normally the thin brown lines which dominate a topo map. Index Contour Lines Are thicker and are labeled with an elevation. Read Between the Lines! The closer the lines are, the steeper the slope. The further, the more gentle Gradient Contour Each of these kids stands upon a different contour line. Yes, it’s imaginary. Get the Idea? With a regular map, we can get the outline of the island, but have no idea as to elevation change (topography). All Elevation Below 10 Feet Under Water Notice how the island has shrank a bit. All Below 20’ Under! All Below 30’ Under! That’s The Idea! Can You Guess The Elevation? Contour Interval Amount of elevation change between each contour line. What is the Contour Interval? Streams Closer Look: Streams Plateaus (Summits) Note: Index, Depression Note: Pond/Lake Various Roads/Highways HILL: AN AREA OF HIGH GROUND. FROM A HILLTOP, THE GROUND SLOPE DOWN IN ALL DIRECTIONS. VALLEY: A STRETCHED-OUT GROOVE IN THE LAND, USUALLY FORMED BY STREAMS OR RIVERS. RIDGE: A SLOPING LINE OF HIGH GROUND. SADDLE: A DIP OR LOW POINT BETWEEN TWO AREAS OF HIGHER GROUND. DEPRESSION: A LOW PO INT IN THE GROUND OR SINKHOLE. THEY ARE REPRESENTED BY CLOSE CONTOUR LINES THAT HAVE TICK MARKS POINTING TOWARD LOW GROUND. DRAW: A LESS DEVELOPED STEAM COURSE THAN A VALLEY. THERE IS ESSENTIALLY NO LEVEL GROUND AND, THEREFORE, LITTLE OR NO MANEUVER ROOM WITHIN ITS CONFINES. ) SPUR: A SHORT, CONTINUOUS SLOPING LINE OF HIGHER GROUND, NORMALLY JUTTING OUT FROM THE SIDE OF A RIDGE. FM 21-26: PAGE 10-12 (FIGURE 10-23) CLIFF: A VERTICAL OR NEAR VERTICAL FEATURE; IT IS AN ABRUPT CHANGE OF THE LAND. THE SLOPE IS SO STEEP THAT THE CONTOUR LINES CONVERGE INTO ONE CONTOUR LINE OR THE LAST CONTOUR LINE HAS TICK MARKS POINTING TO LOW GROUND. CUT: A MAN-MADE FEATURE RESULTIING FROM CUTTING THROUGH RAISED GROUND, USUALLY TO FROM A LEVEL BED FOR A ROAD OR RAILROAD TRACK. FILL: A MAN-MADE FEATURE RESULTING FROM FILLING A LOW AREA, USUALLY TO FORM A LEVEL BED FOR A ROAD OR RAIL- ROAD TRACK.
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