A unit of measurement is simply an arbitrary
length, area, or volume, generally adopted and
agreed upon as a standard unit of measurement.
The basic standard for linear measurement, for
example, is the meter, and the actual length of
a meter is, in the last analysis, equal to the length
of a bar of metal called the International Meter
Bar, one replica of which is kept in the National
Bureau of Standards, Washington, D.C.
As an EA, you will not necessarily be
working with all the units described in this
chapter, and therefore need not attempt to
memorize them all. Many are included simply to
show that units are arbitrary and that there are
many different kinds of units in use.
UNITS OF LINEAR MEASUREMENT
Linear measure is used to express distances
and to indicate the differences in their elevations.
The standard units of linear measure are the foot
and the meter. In surveying operations, both of
these standard units are frequently divided
into tenths, hundredths, and thousandths for
When longer distances are
involved, the foot is expanded into a statute or
to a nautical mile and the meter into a kilometer.
Table 1-1 shows the conversion factors for the
common linear measurements.
In the English system, the most commonly
used basic unit of linear measurement is the foot,
a unit that amounts to slightly more than three-
tenths of the international meter. In what is
called ENGINEERS measurement, the foot is
subdivided decimally; that is, into tenths,
hundredths, or thousandths of a foot. In what is
called CARPENTERS measurement, or English
units, the foot is subdivided into twelfths called
inches, and the inch is further subdivided into
even-denominator fractional parts, as 1/2 in., 1/4
in., 1/8 in., and so on.
Fractions or multiples of the basic 1-ft unit
are used to form larger units of linear measure
of Spanish and Portuguese origin, was formerly
used to measure land boundaries in those areas
of the United States that were at one time under
Spanish control. In those areas old deeds and
other land instruments still contain property
descriptions in varas, which vary from state to
state and country to country from 32 to 43 in.
In many of the non-English-speaking countries
of the world, the most commonly used basic unit
Table 1-1.-Linear Conversion Factors
A unit of linear measurement, called a VARA