LEVEL SURFACEA surface that is parallel
with the spheroidal surface of the earth, such as
a body of still water.
LEVELINGThe operations of measuring
vertical distances, directly or indirectly, to
LINE OF SIGHT1. 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 SYMMETRYA line that divides an
object into two equal identical parts; used only
when the two halves of an object are identical.
LIQUID LIMITThe upper limit of the plastic
state, expressed as the moisture content at which
the flow curve intersects the 25 blows ordinate.
LOGARITHMThe exponent or the power to
which a fixed number, called the base, must be
raised to produce a given number; for example,
LOOP TRAVERSEA closed traverse that starts
and ends at the same station.
MAGNETIC AZIMUTHAn 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
MAGNETIC DECLINATIONThe angular
amount that a magnetic compass needle points
eastward or westward from true north.
MAP MEASUREInstrument used when lengths
of irregular outlines are measured.
MATCH LINESLines 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.
MATHEMATICSThe 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 LEVELThe 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 ANGLESAngles that are either
vertical or horizontal.
MECHANICAL DRAFTINGAny drawing in
which the pen or pencil is guided by a mechanical
MERIDIANA north-south line from which
longitudes (or departures) and azimuths are
MIDPOINTThat 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.
MINUTEA 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.
MONUMENTAny 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 CURVEA curve composed
of a series of extremely small circular arcs of
NON-NORMAL LINEA line that is oblique to
one or more of the planes of projection.