## BEARINGS AND AZIMUTHS

### BEARINGS AND AZIMUTHS

Horizontal angles are angles measured in a horizontal plane by a level instrument
Used to determine:
the locations of points

the orientation of lines

The units of measurement most commonly used in surveying is the *sexagesimal* system
based on degrees, minutes, seconds

### TYPES OF ANGLES

Interior angles
located on the inside of a closed polygon

may be measured clockwise or counterclockwise, but the direction must be consistent throughout

Deflection angles
are measured right or left from an extension of the current line to the next station

are indicated by a numerical value and a "L" or "R"

### DIRECTIONS OF LINES

Defined by a horizontal angle between the line and a defined reference line called a meridian
True meridian is the north-south reference line through the earthÆs geographic poles
Magnetic meridian is a north-south reference line as defined by the earthÆs magnetic field
An assumed meridian can arbitrarily chosen to serve as a reference for all other lines in a survey
### BEARINGS

Designate the direction of a line by an angle and quadrant letters. (e.g. N30° E)
Bearings are never greater than 90°
Bearings are referenced from north or south and the angle to the east or west from the north-south meridian.
True bearings are based on true north.
Magnetic bearings are based on magnetic north.
### TRUE BEARINGS

### BEARING DIRECTION

### MAGNETIC BEARINGS

### AZIMUTHS

Angles measured clockwise from any reference meridian
Azimuths range from 0 to 360°
Azimuths are referenced from north
True azimuths are based on true north
Magnetic azimuths are based on magnetic north