UNITS OF WEIGHT The units of weight most frequently used in the
United States for weighing all commodities except
precious stones, precious metals, and drugs are
the units of the socalled AVOIRDUPOIS system.
Avoirdupois units of weight are as follows:
Precious stones and precious metals are usually
weighed in the United States by the system of
TROY weight, in which there are 12, rather than
16, oz in the pound. Drugs are weighed by APOTHECARIES’
weight, in which there are also 12
oz in the pound.
The basic unit of the metric system of weight is
the GRAM, which contains 15.432 grains. The GRAIN
was originally supposed to be equal to the
weight of a single grain of wheat, The gram of
15.432 grains is also used in the avoirdupois, troy,
and apothecaries’ system of weights. Multiples
and subdivisions of the basic unit of
metric weight (the gram) are named according to
the usual metric system of nomenclature, as follows:
A METRIC TON equals 1,000 kilograms, which
equals 1.1 short tons.
The Engineering Aid is interested in the weight of
his instruments and the pull to be applied to the
ends of the tape to give correct linear measurements.
The common units of weight in surveying
are the OUNCE, the POUND, the GRAM,
and the KILOGRAM. The following tabulation
gives the relationship between these units:
UNITS OF ANGULAR MEASUREMENT
ANGULAR or CIRCULAR MEASURE is used
for designating the value of horizontal and vertical
angles. For general use in the measurement of
angles, the circumference of the circle is divided
into some even number of equal parts. The
unit of angular measure is the angle at the center
of the circle subtended by one of the small subdivisions
of the circumference. The various units
of angular measure are known as UNITS OF
ARCS. In practice these units of arcs may be
further expressed in decimal or fractional parts.
The Engineering Aid may encounter three systems
of angular measure in the use of surveying instruments.
They are the sexagesimal, the centisimal
or metric, and the mil system.
