Chapter 3 Topographic Maps Topography Means: “Shape of the land”

Chapter 3 Topographic Maps

Topography Means:

“Shape of the land”

Contour Lines• Indicate areas of equal elevation• Will never cross or divide

Hill top

– Circles within circles

Specific points are called Benchmarks

Contour interval• Distance between contour lines

500’

Contour Interval Contour Interval = 500’

Indicating all contour lines make it look cluttered – Index Contour Lines

• To get C.I. : Take the Change in Elevation between two contour index lines and divide that by the number of lines between them. C.I. = 250’

You Try!!!

• Map A– C.I. =

• Map B– C.I. =

Benchmark: Exact elevation Marker

Close lines = steep slope

What do you think it looks like from the side?

?

Closed depressions on the land are shown by contour lines with “hachure lines” that point down slope.(indicate holes or craters)

6. A contour line forms a “V” shape

pointing upstream when crossing

a river or stream. Downhill!!!

“V” Shaped

Contour Lines

Steep vs GentleRiver Direction

Gradient = Average rate of slopeDetermined by change in elevation divided by

distance. Rise over Run!

A

B

Scale (km)1km

Elevation Change (rise)=

Distance (run)=

Topographic ProfilingA line that shows the changes in elevation

across a section of a topographic map.

Contouring:

Elevation points have beendetermined using groundsurveying techniques orGPS but contour lines needto be drawn in.