simply driven near the hub or similar marker to
serve as deterrence against machinery or heavy
equipment traffic. On the other hand, permanent
markers are protected by fixed barricades, such
as steel or concrete casing.
METHODS OF DIRECT LINEAR
MEASUREMENTS
One of the most fundamental surveying
operations is the measurement of horizontal
distance between two points on the surface of the
earth. Generally, there are two basic methods
used: direct and indirect. Direct linear measure-
ments, as explained earlier in this chapter, are
methods used for determining horizontal distances
with a tape (or chain) and/or with an electronic
distance-measuring instrument. In indirect
methods, the transit and stadia or theodolite
and stadia are used. This section will discuss
the common methods used in direct linear
measurements.
CHAINING (OR TAPING)
The most common method used in determin-
ing or laying off linear measurements for
construction surveys, triangulation base lines,
and traverse distances is often referred to as
CHAINING. The name is carried over from the
early days when the Gunter’s chain and the
engineer’s chain were in use. Today, it is more
appropriate to call this operation TAPING
because the steel tape has replaced the chain
as the surveyor’s measuring device. In this
manual, however, chaining and taping are used
interchangeably.
Identifying Duties of Chaining
Party Members
Obviously, the smallest chaining party could
consist of only two people—one at each end of
the tape. To lay off a line to a desired distance,
one person holds the zero end of the tape and
advances in the direction of the distant point,
while the other holds a whole number of the tape
at the starting point. The person ahead, holding
the zero end, is called the HEAD CHAINMAN;
the other person is known as the REAR CHAIN-
MAN.
In ordinary chaining operations, if the distance
being measured is greater than a tape length, it
is necessary to mark the terminal point with a
range pole. In this way, the rear chainman can
keep the head chainman aligned at all times
whenever a full tape length or a portion of it is
transferred to the ground.
The head chainman also acts as the recorder,
and the rear chainman is responsible for keeping
the tape in alignment. If more speed or precision
in taping is required, additional personnel are
assigned to the party. This relieves the chainmen
of some of their duties and permits them to
concentrate primarily on the measurement.
For more precise chaining, a three-man party
is essential. In addition to the head and rear
chainmen, a stretcherman is added. The duties of
the stretcherman are to apply and to maintain the
correct tension on the tape while the chainmen
do the measuring. The head chainman still acts
as the recorder and also reads and records the
temperature of the tape.
Either of the two chaining parties described
may have additional personnel assigned as
follows:
. A recorder keeps a complete record of all
measurements made by the taping party, makes
any sketches necessary, writes descriptions of
stations and reference points, and records any
other data required. The head chainman or the
chief of the chaining party may perform these
duties.
. A rodman sets a range pole at the forward
station to define the line to be taped, drives stakes
to mark stations and reference points, carries the
taping stool (discussed later) to the forward point,
and performs other duties as directed.
. One or more axmen clear lines of sight
between stations, cut and drive stakes, and
perform other duties as directed.
. The chief of the chaining party directs the
work of making the tape measurements, the
establishment of stations, and other activities of
the party in the field. The head chainman
performs these duties when there is no separate
party chief.
Coiling and Throwing a Steel Tape
Tapes generally come equipped with a reel;
however, it is not always necessary to replace a
steel tape on the reel at the end of each work
period. A tape can be easily coiled and thrown
into a circular roll.
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