OR/15/057 Principles of laser range finding

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Jones, L D. 2015. Ground-based geomatic surveys at the BGS - a manual for basic data collection & processing (2015). British Geological Survey Internal Report, OR/15/057.

Riegl Terrestrial Laser Measuring Systems are designed for the automatic and manual medium- to-long range capture of digital data for terrain modeling. The LPM scanning system (Figure 1) comprises a laser distance-measuring device mounted on a Pan and Tilt mechanism that rotates 360 degrees around the mounting axis and scans 150 degrees vertically to provide almost total coverage. The VZ scanning system (Figure 2) is a single-axis device that rotates 360 degrees but is limited to 100 degrees scanning arc.

  • Figure 1    LPM-i800HA.
  • Figure 2    VZ-1000.

Both scanning systems are pulse range-finding lasers, incorporating a signal processing unit, a transmitter and a receiver (Figure 3). The scanners are easily attached to a standard survey tribrach and tripod for field usage. The scanning systems are linked via a serial (LMP-2K) or ethernet (LPM-i800HA, VZ-1000) cable to a laptop to enable capture of the digital data.

Figure 3    Laser Scanning system.

Concept

  • ‘Time-of-flight’ method
  • Near-infrared wavelength
  • Pulsed diode laser transmitter
  • Sensitive narrow-band optical receiver
  • Single pulse or multiple pulse signal detection
  • Microprocessor-based post-processing and interfacing

Advantages

  • Small size
  • High reliability
  • High interference immunity
  • High accuracy
  • Long range
  • Quick data acquisition
  • Highly collimated measuring beam

Reduction of the maximum range

  • Very bright daylight
  • Bad visibility
  • Dirty or dusty front lenses