The Effects of Reflecting Surface Material Properties on Time-of-flight Laser Scanner Measurements

Terrestrial laser scanners, such as the Cyrax 2500 and its predecessor the 2400, use pulsed laser ranging and rotating mirrors to accurately measure dense sets of three-dimensional co-ordinates of entire surfaces. Range is observed by measuring the two-way time of flight (TOF) of the reflected laser pulse. The reflectorless nature of the rangefinder raises the possibility of range errors due to pulse attenuation by the reflecting surface. This paper reports on an investigation into the effects of reflecting surface properties on TOF laser scanner measurements made with a Cyrax 2400. Tests were conducted at close range (3m) and medium range (53m). Several samples of construction materials and rocks from Western Australia having various surface roughness and mineral composition were tested with both dry and wet reflecting surfaces. Results presented show no significant range errors due to differing material properties, but do exhibit changes in range measurement distribution and return signal intensity.