TOPOGRAPHIC MAPS
Topographic maps are used to represent a variety of surfaces, especially geographic terrains. They consist of lines of constant
elevation drawn on integral multiples of 5, 10, 50, 100 or more feet of elevation with
the vertical spacing between adjacent contour lines held constant. Thus, the horizontal spacing of the contour lines gives a measure of
steepness of slope in that
they are more closely spaced on steeper slopes.
The principal objective of this exercise is to help students develop the ability to form accurate mental pictures
of land surfaces through the examination of topographic maps. The following examples demonstrate a variety of means of representing
topography.
The following illustrations include a topographic map with two clinographic images drawn as wire mesh surfaces and a stereographic image.
- Typical example of a land surface represented by a topographic map. The contour interval is 5 feet,
and the highest point (elevation 760+ feet) is located near the center of the map.
- Map of the land surface in three dimensions (3-D) viewed from directly above. Use the red/blue lens viewer (blue lens over right eye) to see the
topographic relief.
- Wire mesh representation of the land surface as viewed from above the lower left corner and
looking downward toward the upper right corner. Note that the vertical faces of the block provide topographic profiles
along the left and near sides of the map.
- Wire mesh representation of the land surface as viewed from above the lower right corner and
looking downward toward the upper left corner. Note that the vertical faces of the block provide topographic profiles
along the right and near sides of the map.
The following illustrations include another topographic map with a stereographic image and two clinographic images drawn with stacked contour lines. A topographic
profile color coded to illustrate the method of construction is also included.
- Topographic map with a contour interval of 10 feet. The highest elevation is 530+ feet.
- Inclined view of the map area from the lower left and looking downward toward the upper right. The surface
is represented by stacked contour lines.
- Inclined view of the map area from the lower right and looking downward toward the upper left. The surface
is represented by stacked contour lines.
- 3-D view of the map area viewed from directly above. Use the red/blue lens viewer (blue lens over right eye) to see the
topographic relief.
- Map with a topographic profile constructed along the red line drawn left to right through the area of highest elevation.
The contour interval on the map is 10 feet, and the highest point on the map (and the profile)
is 530+ feet. Topographic profiles illustrate land surfaces as they would appear in silhouette views.
Compare the Geneseo Quadrangle topographic map with the 3-D image (use red/blue lens viewer) of the same terrain provided. The 3-D image covers the southernmost
two thirds of the Geneseo Quadrangle, but it does not include any planimetric (roads, buildings, water bodies, etc.) information with the exception
of the channel of the Genesee River. Look at both representations and try to locate the floodplain
of the Genesee River, the sloping valley walls and the positions of both the Village of Geneseo and Fall Brook .
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