your knee!” thus informing the other chainman
where to hold the end of the tape.
BREAKING TAPE.— The term breaking tape
is used to describe the procedure for measuring
directly horizontal distance on sloping ground, or
through obstacles that do not permit the use of
a full tape length. The procedure used in breaking
tape is the same as ordinary chaining on level
ground, except that the distances are measured
by using portions of a tape, as shown in figure
12-14.
Generally, you will start breaking tape when
the slope of the existing ground exceeds 5 percent
(this depends also on the height of the chainmen).
The reason for breaking tape is that the chainman
on the lower ground will have difficulty in holding
the tape steady and horizontal when his point of
support exceeds his height. You also break tape
to avoid hazardous measurements, such as
crossing power lines and making measurements
across a heavily traveled highway.
Now, to measure the distance AB shown in
figure 12-14, the chainmen may proceed as
follows: The rear chainman stations himself at
point A. The head chainman pulls the tape
forward a full tape length uphill toward point B
and drops it approximately on line with the two
range poles. He then comes back along the tape
until he reaches a point at which a partial tape
length, held level, is below the armpits of the rear
chainman at point A. At this point, the head
chainman selects a convenient whole-foot gradua-
tion, and the chainmen measure off the partial
tape length (distance Aa) from starting point. As
shown in the figure, the head chainman must be
holding at the 60-ft mark to measure Aa. Then,
he calls out, “Holding sixty!” so that the rear
chainman knows what graduation he is holding
when the measurement is made. As in other
chaining methods, the rear chainman always
checks the alignment.
After the pin is placed, the rear chainman
(leaving the tape lying in position) moves forward
to point a and gives a pin to the head chainman
who, in turn, moves to point b; to make sure that
the rear chainman takes the right graduation, he
calls out, “Hold Sixty!” This procedure is
repeated until a full station is measured or until
a full-tape length measurement can be resumed.
You see that to measure distance bc, both
chainmen will probably use plumb bobs to
transfer the distance to the ground.
Remember that the rear chainman gives the
head chainman a pin only at each INTER-
MEDIATE point of a tape length. He keeps the
pin at full tape lengths to keep track of the number
of stations laid out as in ordinary horizontal
chaining.
LAYING OFF A GIVEN DISTANCE.—
Frequently, a chaining party is required to lay off
a given distance and establish a new point on the
ground. This is measuring by using a known
distance on the tape and transferring it to
the ground. If the distance is greater than a
tape length, then the procedure described for
measuring a full tape length is followed for the
Figure 12-14.-Measuring horizontal distances by the “breaking tape” method.
12-15
