ANGLE MEASUREMENTS

MEASURING BY REPETITION

  • Measure the angle (e.g. 73° 21')
  • Tighten the lower motion clamp
  • Re-sight on the initial point
  • Sight the second point and re-measure the angle (e.g. 146° 44')
  • Repeat process as many times as desired
  • Solution equals the average of the measurements, or the final measurement divided by the number of measurements

    REPEATING MEASUREMENTS

  • 1st measurement: 73° 21'
  • 2nd measurement: 146° 44'
  • 3rd measurement: 220° 06'
  • 4th measurement: 293° 29'
  • 5th measurement: 6° 49' (you have gone past 360°, so this is like 366° 49')
  • 6th measurement: 80° 12' (this is like 440° 12')

    CLOSING THE HORIZON

    AZIMUTHS

  • Azimuths are angles that are measured clockwise from a reference direction
  • The reference direction need not be true north or magnetic north
  • Azimuth angles range from 0° to 360°

    MEASURING VERTICAL ANGLES

  • Angles above or below a horizontal through the point of observation (line of sight)
  • Angles above the horizontal plane are called
  • Angles below the horizontal plane are called
  • Theodolites measure zenith angles

    ZENITH ANGLES

  • a reading of 0° corresponds to the telescope pointing vertically (or towards the zenith)
  • the telescope in a horizontal position would read a zenith angle of 90°
  • an angle read with the telescope elevated 30° above the horizon would read a zenith angle of 60°

    A graphic of an Electronic Digital Theodolite is available.