Surveying - Carpenter's and Builder's Math, Plans, and Specifications - page 223

the angle. The transit is set up at the vertex of the angle, the vernier
is clamped at zero, and the telescope is pointed at the target, thereby
marking the direction of the fixed line. The limb is now clamped,
the vernier is unclamped, and the vernier plate is turned through the
desired angle and clamped. A stake should now be driven in line
with the vertical crosshair in the telescope, thus establishing the two
sides of the angle.
When laying out the foundations of buildings, a corner stake
is first located by measurement. Then the direction of one of the
walls is laid out by driving a second stake. This direction may be
determined by local conditions (such as the shape of the lot or the
relation to other buildings). If the building is to be an extension to
(or in line with) another building, the direction can be obtained by
sighting along the building wall and driving two stakes in line with
it. If it is to make a given angle with another building, this angle can
be laid off as shown in Figure 6-11.

STAKE

STAKE

ANGLE MEASURED
WITH TRANSIT

A

M

B

S

C

D

Figure 6-11 The method of laying out a new building (S) at
a given angle with an old building (M). After the corner and
the direction of one wall are determined, a right angle may
be laid off (if the building is rectangular), thus locating two of
the sides (AB and AC). The length of side AB is then mea-
sured, thereby locating corner B. The transit is set up at B,
and line BD is laid off at right angles to AB. AC and BD are
then laid off by the proper length, and the four corners of the
building are thus located. If the building had not been rectan-
gular, the proper angles could have been laid off instead of right
angles.