## 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.

### 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