LESSON 25

• DIRECTION OF A LINE is defined as the horizontal angle the line makes with an established line of reference.
• INTERIOR ANGLES the angle between two adjacent lines in a closed polygon
• When the value of an interior angle is greater than 180° it is referred to as re-entrant angle
• EXTERIOR ANGLES are located outside a closed polygon and are referred to as explements of interior angles.
• The angle between line and the prolongation of the preceding line are called DEFLECTION ANGLE
• ANGLES TO THE RIGHT are measured clockwise from the preceding line to the succeeding line. These are also

  referred to as azimuths from back line.
• BEARING of a line is the acute horizontal angle between the reference meridian and the line
• When directions are measured from the local magnetic meridian they are called MAGNETIC BEARINGS
• If the bearing of a line is observed in the direction of the progress of the survey, it is referred to as FORWARD BEARING, if the bearing of the same line is observed in opposite direction, it is called BACK BEARING.
• Azimuth reckoned from NORTH -ordinary plane surveys
• Azimuth reckoned from SOUTH -large scale geodetic surveys and astronomical observations
• In surveying directions maybe defined by means of:

  INTERIOR ANGLES

  DEFLECTION ANGLES

  ANGLES TO THE RIGHT

  AZIMUTH

  BEARINGS
• AZIMUTH direction given by the angle between the meridian and the line measured in a clockwise direction from either north or south branch of the meridian