05 Angle and Direction Measurement Flashcards
(30 cards)
Components of an Angle
- Reference Line
- Direction of Turn
- Magnitude of Angle Itself
Angles in the Vertical Plane
- Zenith Angle
- Vertical Angle
The angle measured in the
vertical plane
Zenith Angle
The angle measured from the
horizontal
Vertical Angle
Fixed line of reference for determining direction of lines
Meridian
Types of Meridian
- True Meridian
- Magnetic Meridian
- Grid Meridian
- Assumed Meridian
The Meridian where north-south line passing through the geographic poles of the earth
True Meridian
The Meridian where it lies parallel to the magnetic lines of force of the earth and indicated by the direction of the magnetized needle
Magnetic Meridian
The Meridian where line parallel to the central true meridian
Grid Meridian
The Meridian where it is 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 or degree)
The Degree (DMS)
1° = 60’ = 3600’’
Basic unit is degree (°) which is further subdivided into minutes (’) and seconds (”)
The Degree (DMS)
1° = 60’ = 3600’’
Centesimal system is used (circumference of a circle is divided into 400 parts or grads)
The Grad
1g = 100c
1c = 100cc
e.g. 235.2618g = 235g26c18cc
Note: 200g = 180°
Basic unit is grad (g) subdivided into centesimal minutes (c) and centesimal seconds (cc)
The Grad
1g = 100c = 10000cc
e.g. 235.2618g = 235g26c18cc
Note: 200g = 180°
This is defined as the angle subtended at the center of a circle by an arc length exactly equal to the radius of the circle
The Radians
1 radian = 180°/π ≈ 57.2958°
Sometimes referred as the natural angle because there is no arbitrary number in its definition
The Radians
1 radian = 180/π ≈ 57.2958°
Circumference of circle is divided into 6400 parts called ____
The Mils
1600 mils = 90°
Commonly used in military operations as in fire direction of artillery units
The Mils
1600 mils = 90°
What is the equivalent angular unit of 128°15’05” in:
a. Grad
b. Radians
c. Mil
a. Grad - 142g50c15cc
b. Radians - 2.238 rads
c. Mil - 2280.02 mils
The direction of any line with respect to a given meridian. It is indicated by the quadrant in which the line falls and the acute angle that the line makes with the meridian in that quadrant.
Bearing
The direction as given by the angle between the meridian & the line measured in a clockwise direction. On any given survey the direction of zero, this is either always South or always North
Azimuth
Types of Bearing and Azimuth
A. True Bearing and Azimuth
B. Magnetic Bearing and Azimuth
C. Assumed Bearing and Azimuth
The angle between adjacent lines inside a polygon
Interior Angle
