TABLE OF CONTENTS The market of terrestrial laser scanners (TLS) has developed over the last few years quite successfully and the laser scanners are seen as surveying instruments that meet the requirements of detailed topographic maps and industrial applications. TLS can be considered as highly automatic motorized total stations. Unlike total stations however, where the operator directly chooses the points to be surveyed, laser scanners randomly acquire a dense set of points.
TLS provide a sampled representation of a scene by making a series of range measurements in uniform angular increments in both horizontal and vertical planes. The instrument sends a laser burst of light out of an aperture that is pointed at a known azimuth and angle above the ground plane. TLS generate clouds of data so dense that they actually begin to look like images of the objects being mapped (see Figure 2.20).
When the laser burst is reflected back, the distance from the instrument is determined and the 3-D coordinates for each measured point are derived from the basic measurements of range d, horizontal direction ?, and elevation (vertical) angle ?. It is important to note that these coordinates are referenced to the instrument's internally defined system ( x, y
