content page I am going to explore different terms and details involved
with topography and topographic maps.
- "To interpret
topographic maps, contour, township, and range lines must all be introduced.
A contour line is an imaginary line on the Earth connecting points
of equal elevation. The contour interval is the difference
in elevation between any two adjacent contour lines." (Johnston, Aber, &
Ye, 1996, p. 57)
are some important rules regarding contour lines...
"When contour lines cross streams, they bend upstream; that is, the contour
line will "V" in an upstream direction.
Closed contours shown as ellipses or circles represent hills.
Closed contours shown with hachures, short lines pointing downslope, represent
a closed depression with no outlet.
Steep slopes are shown by closely spaced contours, gentle slopes by widely
The difference in elevation between the highest and lowest point of a given
area is known as the maxium relief." (Johnston, Aber, & Ye, 1996, p. 57)
- A globe
is composed of a series of north-south and east-west lines that make
a grid on the Earth. The north-south lines are meridians,
while east-west lines are known as parallels.
- Latitude-longitude and
township-range lines are used for giving locations.
Longitude is measured in degrees east and
west, from the zero, and latitude is measured in degrees
north or south from the equator.
Latitude and longitude are broken into minutes and seconds, with one degree
equal to sixty minutes, one minute equal to sixty seconds. "Topographic
maps, or quadrangles, are classified according to a publication scale.
scale is the relationship of the area on the map to the area on the
Earth's surface. To find the scale of the quadrangle, subtract the difference
in either the latitude or longitude from one side of the map to the other.
1785, government land surveyors adopted a system to locate property lines
and clarify land descriptions on legal documents. This system of coordinates,
used in the U.S., is related to the latitude and longitude system, but
functions independently. The basic block of this system is the section,
one mile long by one mile wide or 640 acres. A township contains 36 sections."
(Johnston, Aber, & Ye, 1996, p. 59)
lines are the north-south lines marking township boundaries, and township
lines are the east-west boundaries. "The letter "T" along
the right-hand margin of the large map stands for the word township, and
the letter "R" stands for the word range.
numbering of townships is based on the intersection of a meridian of longitude
and a parallel of latitude called the principal meridan and base
- To locate
a feature in a given area, the section is divided into quarters, such as
the northeast one-quarter (NE 1/4), the southwest one-quarter (SW 1/4),
etc. Sections could also be divided into halves, such as the north half
(N 1/2). Quarter secions can be further divided into four more quarters
or two halves." (Johnston, Aber, & Ye, 1996, p. 59)