Topographic Maps Textbook Pages 296 - 301
Topographic Maps High Hill Low Hill
Topographic Map What is Topography ? - Topography is the shape of the Earth’s Surface What is a topographic map? • A topographic map shows different shapes and sizes of a land surface using contour lines • Shows 3 dimensional ups and downs on 2 dimensional surface. • Uses? • Useful for hiking and environmental planning (roads, buildings, drainage) • Military • Firefighters • Etc.
Contour Lines • What are contour lines ? • Contour lines are lines of equal elevation • What happens to your elevation if you walk along a contour line? If you walk along a contour line your elevation will not change
Contour Lines • What happens when contour lines are close together? • The closer together the contour lines appear on a topographic map, the steeper the slope • The further apart the contour lines appear on a topographic map, the gentler the slope Since each line is a different elevation what can they never do? Since each contour line is a different elevation, CONTOUR LINES CAN NEVER CROSS
Think of Each line like a new step. If steps are close you go up quickly If steps are spread out you go up slowly
Contour Interval • What is contour interval ? • Contour interval (CI) shows how much each contour line changes by The vertical change in elevation between each contour line What is the Contour Interval for this map? CI = 25 25 ft
Index Contour / Benchmarks • Do we label every line? • Index contours Every 5th line is bold & thicker than others giving elevation. How do we know how High up a specific point is? • Benchmarks are permanent markers of elevation used as reference points.
Topographic maps How do we know which way a river is running? To find river flow use elevation difference (All rivers flow downhill) What if elevation is not shown? Peak Pointers (rule of V’s) -When contour lines cross a stream they bend upstream. The stream flows opposite the V (opens to the mouth). (^ points to peak)
Hachure Marks What if the slope goes down? Hachure marks show areas of lower elevation (depression). - Look like contour lines with Slash lines. -The first Hachure line is the same elevation as the last contour line
Breaking down Lat / Long • Each line of Latitude is about 70 miles. Would this help narrow down your location? • How can we break down Latitude and Longitude? • Each Degree of Lat / Long can be broken down using decimals or minutes and seconds. • 1 Deg = 60 ‘ (minutes) • 1’ = 60 “ (seconds) • 42.958473 deg N or 42 deg 58’45” N
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Be careful reading scale How far apart is this scale?