LASER SCANNERS
• Imaging system provides a user with a dense set of threedimensional vectors to unknown points relative to the scanner
location
• Unprecedented density of geospatial information coverage
• Return-beam detection device
• Beam deflection mechanism.
• Controlled by laptop computer that is also used for data acquisition.
• Range measurement is derived from the two-way travel time of a
laser pulse
• Orientation (elevation and azimuth) of the transmitted
• Pulse is measured by the beam deflection system
• Energy of the return pulse is also recorded
• color (RGB) is also recorded
LASER SCANNER ACCURACY
• BOEHLER, Vincent and Marbs, 2003.
• Tested scanners for accuracy
• Application was for cultural heritage
applications
• Manufacturers specs not comparable
• Angular accuracy
– Angles from combination of deflection of
rotating mirrors and rotation about a mechical
axis
– Provides with range position
• Range accuracy
– Time of flight or phase comparison between
outgoing and returning signal
– Noise-fuzz of points on a flat surface
• Resolution
– User—ability to detect an object in point cloud
– Two specs contribute
• Smallest increment of angle between successive
points (can manually set)
• Size of laser spot
• Edge effects
– When a spot hits and edge and gets 2
locations and or 2 materials
• Surface reflectivity
– Distance, atmospheric, incidence angle
– ,albedo (ability to reflect)
• White strong, black weak
• Depends on spectra of the laser (green, red, near
IR)
• Shiny-poor reflector
– Effects accuracy-range errors larger than
specs
Environmental conditions
• Temperature-check specs
• Atmosphere– changes propagation speed slightly
– Dust, mist, fog-- a problem
• Interfering radiation
– Sunlight strong relative to signal
• Influence or prevent (don’t shoot into sun)
Other considerations
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Measuring speed
Range limits
Field of view
Laser class—eye safe?
Can register?
Can transform into coordinates?
Logistics-weight, batteries etc.
LASER SCANNERS
SCANNER SOFTWARE