Geoscience Reference
In-Depth Information
Visual ConCept CheCk
2.1
Beautiful natural features are scattered around the world
on all seven continents. Locate the following places on a
globe or map of the world and determine the country in
which each one is located.
a)
Mont Blanc, 45.50° N, 6.52° E
b)
Lake Chad, 13.30° N, 14.00° E
c)
Valle de Luna (Valley of the Moon), 23.50° S, 69.00° W
(a)
(b)
(c)
river bends, and rock outcrops. In other words, the survey of
individual land plots was determined on the distance and di-
rection of one tree to another or a river bend to a distinct rock
outcrop. Although this system made some intuitive sense, it was
problematic because landmarks are seldom permanent features,
given that trees die and rivers move. As a result, people could
not depend on the accuracy of the metes and bounds system
over the long term.
After the Revolutionary War ended and settlers began to
spill over from the colonies into areas west of the Appalachian
Mountains, Jefferson and others realized that a more systematic
survey method was required to properly organize the develop-
ing territories to avoid the problems caused by the old metes and
bounds system. The USPLS was first implemented in associa-
tion with the
Northwest Ordinance of 1787
, which established
a rectangular survey system to facilitate the transfer of federal
lands to private citizens in what ultimately became the states of
Ohio, Michigan, Indiana, Illinois, and Wisconsin. The system
proved successful and was further implemented throughout the
rest of the country as settlement progressed. Since the imple-
mentation of the system, almost 1.5 billion acres have been sur-
veyed throughout the country through regulation by the U.S.
Department of the Interior (Bureau of Land Management).
To understand how the USPLS works, it is useful to think
of it as a hierarchical system that is based on an initial set of in-
tersecting lines established within a region of the country, such
as the central Great Plains (Figure 2.9a). This first pair of inter-
secting lines includes a
baseline
, which extends east and west,
and a
principal meridian
, which runs north and south. Once this
pair of lines was established, surveyors then created a second-
ary grid by surveying lines every 6 mi along each baseline and
principal meridian (Figure 2.9b). Lines surveyed along the prin-
cipal meridian (extending east and west) are called township
lines, whereas those along the baseline (extending north and
south) are called range lines. The intersection of township and
range lines—remember all are 6 mi apart—resulted in a grid
network that consisted of a series of 36 mi
2
tracts. Each of these
36 mi
2
tracts is called a
township
, with each township identified
with a township and range designation. Township designations
indicate the location north or south of the baseline, whereas
range designations indicate the location east or west of the prin-
cipal meridian. So, for example, a township might be identified
as Township 2 South, Range 3 West, which would mean that it
was in the second tier of townships south of a baseline, and in
the third column of townships west of a principal meridian.
Once the grid of townships was established, they were
further subdivided by survey into thirty-six 1 mi
2
tracts
(Figure 2.9b). Each of these tracks is called a
section
and con-
tains 640 acres. They are numbered sequentially within each
township, beginning with Section 1 in the upper right corner
and Section 36 in the lower right. (Section 14 is identified in
Figure 2.9b). It is these sections that you see when you fly
over much of the country (Figure 2.9c), with roads marking
the edge of each 1 mi
2
tract of land. It is also why roads in
rural areas are usually at right angles to each other because
they intersect at section corners. Sections can be further sub-
divided into ½ sections (320 acres) or ¼ sections (160 acres
Figure 2.9b). Such ¼ sections were the base land unit of the
