CLOSING THE HORIZON—Measuring the last
of a series of horizontal angles at a station
required to make the series complete around the
horizon. At any station, the sum of the horizontal
angles between adjacent lines should equal 360°.
The amount by which the sum of the measured
angles fails to equal 360° is the angular error of
closure. This error is distributed as a correction
among the measured angles to make their sum
exactly 360°. The error and the correction have
opposite algebraic signs.
COLLIMATE—Adjust the line of sight of a
telescopic surveying instrument to its proper
position relative to the other parts of the
instrument.
COLLIMATION LINE—The line through the
second nodal point of the objective (object glass)
of a telescope and the center of the reticle. It is
variously termed the line of sight, sight line,
pointing line, and the aiming line of the instru-
ment. The center of the reticle of the telescope
of a transit can be defined by the intersection of
cross hairs or by the middle point of a fixed
vertical wire or of a micrometer wire in its mean
position. In a leveling instrument, the center of
the reticle may be the middle point of a fixed
horizontal wire.
COMMON LOGARITHMS—Logarithms with
10 as a base.
COMPASS-PIVOT JOINT, BOW, DROP
BOW, BEAM—Instrument used to draw circles
or arcs of circles.
COMPOUND CURVE—A curve composed of a
series of successive tangent circular arcs.
CONE—A solid figure that tapers uniformly from
a circular base to a point.
CONNECTING TRAVERSE-A closed traverse
that starts and ends at different stations whose
relative positions have been determined by other
surveys.
CONSTRUCTION LINES—Lightly drawn lines
used in the preliminary layout of a drawing.
CONTOUR—An imaginary level line (constant
elevation) on the ground surface; it is called a
CONTOUR LINE on a corresponding map.
CONTOUR INTERVAL—A predetermined
difference in elevation (vertical distance) at which
contour lines are drawn. The contour interval is
usually the same for maps of the same scale.
CONTOUR LINE—An imaginary line on the
ground, all points of which are at the same
elevation above or below a specified datum.
CONTOUR MAP—A map that portrays relief by
means of contour lines.
CONTROL—A system of points whose relative
positions have been determined from survey
data. (See BASIC CONTROL, HORIZONTAL
CONTROL, and VERTICAL CONTROL.)
CONTROL STATION—A station whose posi-
tion (horizontal or vertical) has been determined
from survey data and is used as a base for a
dependent survey.
CONTROL SURVEY—A survey that provides
positions (horizontal or vertical) of points to
which supplementary surveys are adjusted.
COORDINATES—Linear or angular quantities,
or both, that designate the position of a point in
relation to a given reference frame. There are two
general divisions of coordinates used in surveying:
polar coordinates and rectangular coordinates.
These may be subdivided into three classes: plane
coordinates, spherical coordinates, and space
coordinates.
COUNTERCLOCKWISE ANGLE—A hori-
zontal angle measured in a counterclockwise
direction. The counterclockwise angle is used
primarily for the measurement of deflection
angles.
COURSE—The direction of a line with reference
to a meridian, usually given as a true or as a
magnetic bearing.
CRUSHED GRAVEL-The product resulting
from the artificial crushing of gravel with
substantially all fragments having at least one face
resulting from fracture.
CRUSHED STONE—The product resulting from
the artificial crushing of rocks, boulders, or large
cobblestones, substantially all faces of which have
resulted from the crushing operation.
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