Lesson 5: Angle and Direction Measurements

Question 1

Components of an Angle

Answer 1

1. Reference line
2. Direction of the turn
3. Magnitude of the angle itself

Question 2

Angles in the Vertical Plane

Answer 2

1. Zenith Angle – angle measured in the
   vertical plane
2. Vertical Angle – angle measured from the
   horizontal
3. Interior Angle
4. Deflection Angle
   - angle between the line and the prolongation
   of the preceding line
5. Angle to the Right
   - measured clockwise from the preceding to the
   following line

Question 3

Fixed line of reference for determining
direction of lines

Answer 3

Meridian

Question 4

Types of Meridian

Answer 4

1. True Meridian
2. Magnetic Meridian
3. Grid Meridian
4. Assumed Meridian

Question 5

north-south line passing through
the geographic poles of the earth

Answer 5

True Meridian

Question 6

lies parallel to the magnetic lines of force of the earth and is indicated by the direction of the magnetized needle

Answer 6

Magnetic Meridian

Question 7

line parallel to the central
true meridian

Answer 7

Grid Meridian

Question 8

arbitrarily chosen for convenience

Answer 8

Assumed Meridian

Question 9

Units for Measuring Angles

Answer 9

1. Degree
2. Grad
3. Radians
4. Mil

Question 10

• Sexagesimal system is
  used (circumference of a
  circle is divided into 360
  parts)

Answer 10

The Degree (DMS)

Question 11

The centesimal system is used (circumference of a circle is divided into 400 parts)

Answer 11

The Grad

Question 12

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

Answer 12

The Radians

Question 13

Circumference of circle is divided into 6400
parts

Commonly used in military operations as in
fire direction of artillery units

Answer 13

The Mil

Question 14

• 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

Answer 14

Bearing

Question 15

Three types of bearing

Answer 15

a. True bearing
b. Magnetic bearing
c. Assumed bearing

Question 16

• direction as given by the angle between the
  meridian & the line measured in a clockwise
  direction
• on any given survey the direction of zero
  azimuth is either always South or always North

Answer 16

Azimuth

Question 17

Three types of Azimuth

Answer 17

a. True azimuth
b. Magnetic azimuth
c. Assumed azimuth

Question 18

angle between adjacent lines inside a polygon

Answer 18

Interior Angle

Question 19

angle between the line and the prolongation
of the preceding line

Answer 19

Deflection Angle

Question 20

measured clockwise from the preceding to the
following line

Answer 20

Angle to the Right

Question 21

Instruments for Angle and Direction
Measurement

Answer 21

1. Tape
2. Magnetic Compass
3. Engineer’s Transit
4. Theodolite
5. Total Station

Question 22

The angle between the true meridian and
the magnetic meridian

Answer 22

Magnetic Declination

Question 23

Variations in Magnetic Declination

Answer 23

1. Secular Variation
2. Annual Variation
3. Daily Variation
4. Irregular Variation

Question 24

the magnetic meridian swings in one direction for perhaps 150 yrs until it gradually comes to rest and then swings in the other direction, due to an unexplainable phenomenon

Answer 24

Secular Variation

Question 25

small annual swing distinct from secular variation; the value is less than a minute

Answer 25

Annual Variation

Question 26

periodic swing of the magnetic needle occurring each day

Answer 26

Daily Variation

Question 27

due to magnetic storms and disturbances caused by solar flares

Answer 27

Irregular Variation

Question 28

Steps in Closed Compass Traverse Adjustments

Answer 28

1. Compute and Adjust interior angles 2. Select the best line (line in the traverse w/c is unaffected by local attraction) 3. Adjust observed bearings of successive lines