Lesson 5: Angle and Direction Measurements Flashcards
Components of an Angle
- Reference line
- Direction of the turn
- Magnitude of the angle itself
Angles in the Vertical Plane
- Zenith Angle – angle measured in the
vertical plane - Vertical Angle – angle measured from the
horizontal - Interior Angle
- Deflection Angle
- angle between the line and the prolongation
of the preceding line - Angle to the Right
- measured clockwise from the preceding to the
following line
Fixed line of reference for determining
direction of lines
Meridian
Types of Meridian
- True Meridian
- Magnetic Meridian
- Grid Meridian
- Assumed Meridian
north-south line passing through
the geographic poles of the earth
True Meridian
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
arbitrarily chosen for convenience
Assumed Meridian
Units for Measuring Angles
- Degree
- Grad
- Radians
- Mil
- Sexagesimal system is
used (circumference of a
circle is divided into 360
parts)
The Degree (DMS)
The centesimal system is used (circumference of a circle is divided into 400 parts)
The Grad
is defined as the angle subtended at
the center of a circle by an arc length exactly equal to the radius of the circle
Sometimes referred to as the natural angle
because there is no arbitrary number in its
definition
The Radians
Circumference of circle is divided into 6400
parts
Commonly used in military operations as in
fire direction of artillery units
The Mil
- direction of any line with respect to a given
meridian - indicated by the quadrant in which the line
falls and the acute angle that the line makes
with the meridian in that quadrant
Bearing
Three types of bearing
a. True bearing
b. Magnetic bearing
c. Assumed bearing
