ALTM Technical Overview
Multipulse is a revolutionary approach to overcoming altitude constraints as a function of the timing limit associated with time-of-flight laser
measurements. The timing limit refers to the time it takes for a pulse of light to travel from the laser transmitter, to the target, and back to the receiver.
Traditionally, lidar sensors wait for the transmitted pulse to return to the receiver before emitting the next pulse. Consequently, the laser pulse rate
directly limits the system operating altitude.
CMP™ technology enables two or more pulses to be emitted and tracked, significantly increasing survey coverage rates, without the hassle of
planning around the data “blind zones” common to other multipulse technologies.
A high-accuracy laser rangefinder is mounted over an opening in the aircraft floor. The rangefinder scans beneath the aircraft, producing a wide swath over which the distance to the ground is measured. The angle at which the laser is scanned is also measured.
To correct for the aircraft's movements, the motions of the aircraft are recorded by an inertial reference system for later post-processing. The laser can also be installed on a stabilized platform.
A GPS receiver in the aircraft records the aircraft's position at fixed intervals. A second, ground-based receiver provides differential correction for a more accurate position estimate.
In post-flight processing, the laser range, scan angle, GPS data and IRS data are combined to accurately determine the position of a point on the Earth's surface.