LASER SCANNERS Imaging system provides a user with a dense set of three- dimensional 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, 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 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