Topographic notes Topographic Map-includes contour lines drawn
to represent changes in elevation. Topographic maps take 3
dimensional ups and downs of the terrain and show them on 2
dimensional surface. When reading a topographic map you need to
visualize in your minds eye on a 3-D map view of what the symbols
and the contour lines are representing.
Slide 3
Topographic Notes When you follow a path on a topographic map
that crosses these contour lines, you will either be climbing or
descending. A path running parallel to contour lines are relatively
flat. The MOST important thing to remember: CLOSE contour lines
mean STEEP terrain OPEN contour lines mean FLAT terrain
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Slide 5
Contour line and interval Contour line- lines that connect
points of equal elevation. The red arrows are pointing to the index
contour lines. Notice that they are wider than the other lines. The
number in each circle shows the elevation of the index contour
lines.
Slide 6
Contour Lines and intervals Rules to reading a topographic map
Where a contour line crosses a stream or valley, the contour line
bends to form a V that points upstream. In the upstream direction,
the successive contours represent higher elevations. Contour lines
near the top of a hill form closed, circular shapes. The top of the
hill is higher than the highest closed contour line. Depressions
without outlets are shown by closed hatched contours. The contour
lines have short lines on the inside that are pointing downslope.
The bottom of the depression is lower than the lowest closed
contour line.
Slide 7
Contour lines and intervals Contour lines are widely spaced on
gentle slopes. Contour lines are closely spaced on steep slopes.
Contour lines DO NOT cross or intersect each other, except in the
rare case of an overhanging cliff. All contour lines eventually
will make a closed loop. This closure may be on the map or beyond
its margins since contour lines connect features of the same
elevation.
Slide 8
Scale and Interval A scale of 1:24,000 is 1 inch on the map =
24,000 inches on the ground= 2,000 ft or.38 miles. The scale and
interval are usually found in the margin of the map.
Slide 9
Benchmark - Accurate measurements of location and the elevation
are recorded in the brass and placed on rock or concrete to help
surveyors and mapmakers (cartographers) draw maps.
Slide 10
Topographic vs. Satellite Blue = water features Green=
woodlands, orchards, or other vegetation Red or grey= urban areas,
important roads Black= man made works, road boundaries (solid or
dotted lines) Brown= Contour lines
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Slide 12
Topographic vs. Satellite Satellite images allow map makers and
scientists to more easily view and measure the topography of the
Earths crust. Limitations: They do not show measured changes in
elevation.