CONTENT PAGE

By Katie Solon

On this 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)

Here are some important rules regarding contour lines...

1.   "When contour lines cross streams, they bend upstream; that is, the contour line will "V" in an upstream direction.
2.   Closed contours shown as ellipses or circles represent hills.
3.   Closed contours shown with hachures, short lines pointing downslope, represent a closed depression with no outlet.
4.   Steep slopes are shown by closely spaced contours, gentle slopes by widely spaced contours.
5.   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.
• Map 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.
• After 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)
• Range 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.
• The numbering of townships is based on the intersection of a meridian of longitude and a parallel of latitude called the principal meridan and base line, respectively.
• 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)