LEVEL SURFACE—A surface that is parallel
with the spheroidal surface of the earth, such as
a body of still water.
LEVELING—The operations of measuring
vertical distances, directly or indirectly, to
determine elevations.
LINE OF SIGHT—1. The straight line between
two points. This line is in the direction of a great
circle, but it does not follow the curvature of the
earth. 2. The line extending from an instrument
along which distant objects are seen when viewed
with a telescope or other sighting device.
LINE OF SYMMETRY—A line that divides an
object into two equal identical parts; used only
when the two halves of an object are identical.
LIQUID LIMIT—The upper limit of the plastic
state, expressed as the moisture content at which
the flow curve intersects the “25 blows” ordinate.
LOGARITHM—The exponent or the power to
which a fixed number, called the base, must be
raised to produce a given number; for example,
common log
LOOP TRAVERSE—A closed traverse that starts
and ends at the same station.
MAGNETIC AZIMUTH—An azimuth measured
with reference to the direction indicated by a
magnetic compass needle. Magnetic azimuth is
measured from magnetic north, which is east or
west of true north, as shown by the magnetic
declination.
MAGNETIC DECLINATION—The angular
amount that a magnetic compass needle points
eastward or westward from true north.
MAP MEASURE—Instrument used when lengths
of irregular outlines are measured.
MATCH LINES—Lines used when an object is
too large to fit on a single drawing sheet and must
be continued on another sheet. The points where
the object stops on one sheet and continues
on the next sheet must be identified with
corresponding match lines. They are medium
weight lines indicated with the words match line
and referenced to the sheet that has the cor-
responding match line.
MATHEMATICS—The science that deals with
the relationships that exist between quantities and
operations, and with methods by which these
relationships can be applied to determine
unknown quantities from given or measured data.
MEAN SEA LEVEL—The average height of the
sea for all stages of the tide. Mean sea level at
numerous tide-gaging stations usually forms the
basis of a level datum for large areas.
MEASURED ANGLES—Angles that are either
vertical or horizontal.
MECHANICAL DRAFTING—Any drawing in
which the pen or pencil is guided by a mechanical
device.
MERIDIAN—A north-south line from which
longitudes (or departures) and azimuths are
reckoned.
MIDPOINT—That point on the arc of a circular
curve that is the same distance from both ends
of the arc.
MILITARY STANDARDS (MIL-STDs)—
Instructions set forth by the Department of
Defense that members of all armed services are
required to follow. Only a few of these standards
refer directly to drafting.
MINUTE—A 60th part of a degree used to define
the size of an angle.
MOISTURE CONTENT (w.)—The ratio,
expressed as a percentage, of the weight of water
in a given soil mass to the weight of solid particles.
MONUMENT—Any object or collection of
objects that indicates the position on the ground
of a survey station. In military surveys, the term
monument usually refers to a stone or concrete
station marker containing a special bronze plate
on which the exact station point is marked.
NONCIRCULAR CURVE—A curve composed
of a series of extremely small circular arcs of
varying radii.
NON-NORMAL LINE—A line that is oblique to
one or more of the planes of projection.
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