LECTURE 5 Flashcards
angle measured in the
vertical plane
zenith angle
angle measured from the
horizontal
vertical angle
Fixed line of reference for
determining direction of lines
meridian
north-south line passing through the geographic poles of the earth
true meridian
meridian that lies parallel to the
magnetic lines of force of the earth and
is indicated by the direction of the
magnetized needle
magnetic meridian
line parallel to the central true meridian
grid meridian
meridian arbitrarily chosen for convenience
assumed meridian
Units for measuring angles
- Degree
- Grad
- Radians
- Mil
Sexagesimal system is used
DMS
the angle subtended at the center of a
circle by an arc length
Radians
Sometimes referred as the
natural angle
Radians
Commonly used in military operations as in
fire direction of artillery units
Mil
Direction of any line with respect to
a given meridian
Bearing
Direction as given by the angle between the meridian & the line measured in a clockwise direction
Azimuth
Angle between adjacent lines inside a polygon
Interior angle
Angle between the line and the prolongation of the preceding line
Deflection angle
Measured clockwise from the preceding line to the following line
Angle to the right
Instruments for Angle
Measurement
- Tape
- Magnetic Compass
- Engineer’s Transit
- Theodolite
- Total Station
The angle between the true meridian
and the magnetic meridian
Magnetic declination
variation of magnetic declination in which the magnetic meridian swings in one direction for 150 yrs until it gradually comes to rest and then swings in the other direction
Secular variation
small annual swing distinct from secular variation; the value is less than a minute
Annual variation
Periodic swing of the magnetic
needle occurring each day
Daily Variation
Magnetic declination variation due to magnetic storms and disturbances caused by solar flares
Irregular variation
