Laser Scanning Jargon

Harriet Brewitt

Laser scanning technology may sound complicated but sometimes it’s just about knowing the right terminology. This quick guide can help you to understand more about 3D laser scanners and how they work.

Click the letters to see the terms alphabetically. If you think we're missing any words, please drop us a line

 

Accuracy: This can be described as the degree of closeness of measured quantity to its true value. Accuracy shouldn’t be confused with precision. Read more on the Accuracy and Precision blog.

Amplitude: The raw measurement of the power strength of the return echo. It is the value of the power of the light that we receive back from the target. Later on, during real-time post processing, we receive amplitude which is defined as the ratio of the actual detected optical amplitude of the echo pulse versus detection threshold of the instrument. Thus, the value of the amplitude reading is a ratio, given in the units of decibel (dB). By introducing amplitude readings in this way we can use it to improve the object classification. Amplitude depends on the distance, further away the scanner is from the target the less power it receives.

Angle of incidence: Assuming a locally flat target (approximated by a plane), the angle of incidence is the angle between laser axis and the plane’s normal vector.

Angular resolution: This is a parameter of the scan mechanism. It corresponds to the minimum possible angular distance between two consecutive laser measurements.

Beam diameter / beam width: The diameter of the laser beam perpendicular to the beam axis. Since beams typically do not have sharp edges, the diameter can be defined in many different ways. RIEGL uses the 1/e² definition, which is in common use for Gaussian beams, (Beams with a Gaussian power density distribution).

Beam divergence (angular width): An angular measure of the increase in beam diameter with distance from the optical centre from which the laser beam emerges. Angular width is an angle described by the beam at the source.  In RIEGL instruments beam divergence is usually given in mrad for each 100m distance (for instance 0.25 mrad corresponds to 25 mm increase of beam width per 100m).

BDS: BeiDou Navigation Satellite System is a Chinese satellite navigation system. It consists of two separate satellite constellations – a limited test system that has been operating since 2000, and a full-scale global navigation system that is currently under construction.

Coordinate System: Coordinate systems enable geographic datasets to use common locations for global positioning. A coordinate system is a reference system used to represent the locations of geographic features, imagery and observations.