Lab 9 Topo Maps

What is a Topographic Map?

-
2D representation
of 3D space.

-
Uses contour
lines to represent areas of equal elevation.

What is a Contour Line?

-
Line on a map
representing equal elevation, shows the relief

-
contour lines do
not cross

-
Contour Interval
is the spacing of contour lines.

-
Bold lines are
called “Index Contours” labeled w/ elevation

Rules of Contour Lines: Fig
9.5

Relief:

-
Difference in
elevation between two points on the earth

-
Gradient =
steepness of a slope ft/mi ( relief / distance )

-
Local relief is
the difference in elev between two points

-
Total relief is
the diff between the highest and lowest pts on map

Scales:

-
Ratio and
Fractional scales show the equivalence of a map measurement to the actual
distance on earth.  ex- on a 1:10000 scale map, one of any unit equals 10000 of
the same unit on earth.

-
Ratio =
Fractional scales
ie. 1:1500 = 1/1500

-
Conversions
within scales

ex-
1:25000 scale map.  One inch on the
map equals 25000 inches on earth, or 4.7 miles on the earth

Topographic Profiles:

-A crossectional view created from the topo map.

Latitude and Longitude:

-An
artificial grid projected onto the earth that can be used to calculate exact
locations.

-Latitude
lines run horizontal and start at 0 at the equator and increase out toward each
pole.

-Longitude
line run vertical beginning at the Prime Meridian (Greenwich
England)
and increase out east and west

True North vs Magnetic North:

-True North
refers to the North pole as determined graphically

-Magnetic
North is the direction your compass points, about N.
Greenland.

Compass Bearing and
Declination:

-Declination
is the difference in degrees between the magnetic north and grid (true) north

-Bearing
is a compass direction expressed in degrees away from zero.

ex-
directly east would be a compass bearing of 90o

Public Land Survey (Township and Range):

-Another
type of grid used in the United
States to partition land into smaller and
smaller pieces.  Can also be used to
locate positions on maps