Reading Topographic MapsReading Topographic Maps

TopographyTopography

The lay of the land.The lay of the land. Shows relief using contour lines.Shows relief using contour lines.

– Relief- highs and lows of Earth’s surface.Relief- highs and lows of Earth’s surface.– Relief can be calculatedRelief can be calculated

Take the difference between the highest Take the difference between the highest point and the lowest.point and the lowest.

– Ex: Mountain peak 20 m. lake 10mEx: Mountain peak 20 m. lake 10m– 20m- 10m= 10m20m- 10m= 10m– The relief of this area is 10mThe relief of this area is 10m

Contour LinesContour Lines Lines on topographic maps.Lines on topographic maps. Connect points of equal elevation.Connect points of equal elevation.

– Everything connected to that line has Everything connected to that line has the same elevation.the same elevation. Elevation- the distance something is above Elevation- the distance something is above

sea level. Sea level= 0m or 0ft. sea level. Sea level= 0m or 0ft.

Contour IntervalsContour Intervals

Contour interval- gives the difference Contour interval- gives the difference in elevation between 2 contour lines.in elevation between 2 contour lines.– Another indicator of height.Another indicator of height.

C.I.= 1000ft

How it will look on a map

Index ContoursIndex Contours Index contours occur every fifth contour Index contours occur every fifth contour

line; accentuated in thickness .line; accentuated in thickness . Help the map user read elevations on a Help the map user read elevations on a

map. map.

Red arrows indicate location of index contours.

StreamsStreams

Streams are shown as a blue Streams are shown as a blue line on maps.line on maps.

When contour lines cross a When contour lines cross a stream it looks like an upside stream it looks like an upside down V.down V.

The point in the V points The point in the V points upstream. It opens in the upstream. It opens in the

direction the direction the water is flowing.water is flowing.

Depression ContoursDepression Contours

Depression contours Depression contours show areas of lower show areas of lower elevation.elevation.

Drawn like contour Drawn like contour lines with marks on lines with marks on the inside. the inside.

HillsHills Hills are represented on a topographic Hills are represented on a topographic

map by a series of concentric contour lines map by a series of concentric contour lines in a rough circle in a rough circle

SlopeSlope Closely spaced contour lines represent Closely spaced contour lines represent

steep slopes.steep slopes. Widely spaced contour lines represent Widely spaced contour lines represent

gentle slopes. gentle slopes.

Colors on a topographic map- Colors on a topographic map-

– Blue = water Blue = water – Green = forest Green = forest – Brown = contour lines Brown = contour lines – Black = cultural features (buildings, place Black = cultural features (buildings, place

names, boundary lines, roads, etc.) names, boundary lines, roads, etc.) – Red = principal roads Red = principal roads – Pink = urban areas Pink = urban areas – Purple = revisions to an older map, compiled Purple = revisions to an older map, compiled

from aerial photos. If an area has become from aerial photos. If an area has become urbanized, this may be shown as purple shading urbanized, this may be shown as purple shading on the new, revised map. on the new, revised map.

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