Page 93 - Calculating Agriculture Cover 20191124 STUDENT - A

CH 9] Calculating Agriculture 9-3

Public land survey system (PLSS) The Public Land Survey System uses a grid system that
consists of Baselines, Meridians, Townships, and Sections. From these ½ sections, ¼ sections, block
maps, and property descriptions are derived.
A baseline is a latitudinal line between two points on the earth's surface and the direction and
distance between them. In the United States Public Land Survey System, a baseline is the principal
east-west line (i.e., a parallel) upon which all rectangular surveys in a defined area are based. The
baseline meets its corresponding principal meridian at the point of origin, or initial point, for the land
survey. For example, the baseline for Nebraska and Kansas is shared as the border for both states, at
the 40th parallel north. More specifically a baseline may be the line that divides a survey township
between north and south.
Many communities in the United States have roads that run along survey baselines, many of
which are named to reflect that fact. Some examples:
 In Little Rock, Arkansas, Baseline Road follows the baseline used by surveyors of the
Louisiana Purchase.
 In Colorado, Baseline Road in Boulder marks the 40th parallel, or the western extension of
the Kansas-Nebraska boundary, which is also the boundary between Adams and Weld
counties.
 In Arizona, the baseline near the Phoenix metro area is marked by Baseline Road.
 In Southern California, from Highland to San Dimas, the baseline is marked by Baseline
Road and runs through the city of San Bernardino.
 In Michigan, the baseline for the Michigan Survey forms the boundary between the second
and third tiers of counties and in many portions, discontinuous segments of road along the
baseline are known as "Baseline Road." 8 Mile Road in the Detroit area runs along the
Michigan Baseline and was formerly known as "Baseline Road."
 Baseline Road in Hillsboro, Oregon, generally follows the Willamette Baseline which
intersects the Willamette Meridian at the Willamette Stone State Park.
Principal Meridians and Base Lines
There are 37 Principal Meridians. Each Principal Meridian is named and these names are used to
distinguish the various surveys. Meridians are imaginary lines of longitude on the earth that extend
from the North to South Pole. A Principal Meridian is one which is used as a reference line to survey
a large area. The east-west line that intersects the initial point is called a base line. This line is
perpendicular to the Principal Meridian. Each township is identified with a township and range
designation. This section will only discuss a few Principal Meridians for clarity.
In Illinois, for example, the Third Principal Meridian, Figure 9.3, which roughly cuts it in two, is
located about 9 miles west of the 89th geographic meridian. It was established as a line running true
north from the point of confluence of the Ohio and Mississippi Rivers. Its exact location is 89
degrees, 10 minutes and 30 seconds west of Greenwich, England. Greenwich is the starting point for
all longitudinal measurements since longitude 0 degrees passes through it.
The Fourth Principal Meridian was established for surveying lands located between the Illinois
and Mississippi Rivers. It begins at a point near Beardstown and is along a line straight north from
the mouth of the Illinois River near Grafton. The longitudinal reading of this line is 90 degrees, 28
minutes, and 45 seconds west.
The Second Principal Meridian, used in descriptions of some land in Illinois and is located in
Indiana. Its reading is 86 degrees, 28 minutes, and 0 seconds west.
Not all principal meridians are numbered. Some, such as the Michigan and Louisiana Meridians,
are named for the state in which they are located. Others are named for territorial features; for
example, the Indian Meridian in Oklahoma and the Salt Lake Meridian in Utah. There are over thirty
principal meridians in the United States.
Principal meridians do not always extend from one state into another. The Third Principal
Meridian is located entirely within Illinois; the Fourth Principal Meridian, however, extends into
Wisconsin and is the reference line for all land descriptions in Wisconsin and for some in northeast 9
Minnesota.

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