05 Angle and Direction Measurement

Question 1

Components of an Angle

Answer 1

1. Reference Line
2. Direction of Turn
3. Magnitude of Angle Itself

Question 2

Angles in the Vertical Plane

Answer 2

1. Zenith Angle
2. Vertical Angle

Question 3

The angle measured in the
vertical plane

Answer 3

Zenith Angle

Question 4

The angle measured from the
horizontal

Answer 4

Vertical Angle

Question 5

Fixed line of reference for determining direction of lines

Answer 5

Meridian

Question 6

Types of Meridian

Answer 6

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

Question 7

The Meridian where north-south line passing through the geographic poles of the earth

Answer 7

True Meridian

Question 8

The Meridian where it lies parallel to the magnetic lines of force of the earth and indicated by the direction of the magnetized needle

Answer 8

Magnetic Meridian

Question 9

The Meridian where line parallel to the central true meridian

Answer 9

Grid Meridian

Question 10

The Meridian where it is arbitrarily chosen for convenience

Answer 10

Assumed Meridian

Question 11

Units for Measuring Angles

Answer 11

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

Question 12

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

Answer 12

The Degree (DMS)

1° = 60’ = 3600’’

Question 13

Basic unit is degree (°) which is further subdivided into minutes (’) and seconds (”)

Answer 13

The Degree (DMS)

1° = 60’ = 3600’’

Question 14

Centesimal system is used (circumference of a circle is divided into 400 parts or grads)

Answer 14

The Grad

1g = 100c
1c = 100cc
e.g. 235.2618g = 235g26c18cc

Note: 200g = 180°

Question 15

Basic unit is grad (g) subdivided into centesimal minutes (c) and centesimal seconds (cc)

Answer 15

The Grad

1g = 100c = 10000cc
e.g. 235.2618g = 235g26c18cc

Note: 200g = 180°

Question 16

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

Answer 16

The Radians

1 radian = 180°/π ≈ 57.2958°

Question 17

Sometimes referred as the natural angle because there is no arbitrary number in its definition

Answer 17

The Radians

1 radian = 180/π ≈ 57.2958°

Question 18

Circumference of circle is divided into 6400 parts called ____

Answer 18

The Mils

1600 mils = 90°

Question 19

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

Answer 19

The Mils

1600 mils = 90°

Question 20

What is the equivalent angular unit of 128°15’05” in:
a. Grad
b. Radians
c. Mil

Answer 20

a. Grad - 142g50c15cc
b. Radians - 2.238 rads
c. Mil - 2280.02 mils

Question 21

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.

Answer 21

Bearing

Question 22

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

Answer 22

Azimuth

Question 23

Types of Bearing and Azimuth

Answer 23

A. True Bearing and Azimuth
B. Magnetic Bearing and Azimuth
C. Assumed Bearing and Azimuth

Question 24

The angle between adjacent lines inside a polygon

Answer 24

Interior Angle

Question 25

The angle between the line and the prolongation of the preceding line

Answer 25

Deflection Angle

Question 26

The measured clockwise from the preceding to the following line

Answer 26

Angle to the Right

Question 27

Instruments for Angle and Direction Measurement

Answer 27

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

Question 28

The angle between the true meridian and the magnetic meridian

Answer 28

Magnetic Declination

Question 29

Variations in Magnetic Declination

Answer 29

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

Question 30

Steps in Closed Compass Traverse Adjustments

Answer 30

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