Sensors: Image Processing Library
Laser altimeters or light detection and ranging (LIDAR) systems, which are active optical sensors that generate energy using lasers, are also being developed for extremely high-resolution topographic mapping. The basis of LIDAR sensing is simple. The time interval between when the laser pulse is generated and received back at the antenna after reflecting from a target on the ground is recorded. With precise knowledge of the aircraft position computed using the Global Positioning System (GPS), topography can then be inferred very accurately. As an active sensor, LIDAR can be flown at night, but unlike SAR, it is unable to penetrate clouds.
LIDAR pict here
The LIDAR system combines a pulsed, solid-state laser, an inertial motion unit (IMU), and a geodetic GPS receiver in a compact and modular configuration. The IMU (accelerometers and gyroscopes) monitors the aircraft attitude, while the GPS receiver provides aircraft position data. Rotating optics in the instrument's sensor head scans the laser across the ground, illuminating a swath under the aircraft. The LIDAR instrument can be installed on any plane equipped for aerial photography. Depending upon aircraft altitude, aircraft velocity, and instrument pulse rate, the LIDAR instrument can collect data with an illuminated footprint of approximately 15 cm and a swath width ranging from 300 to 900 meters.
Last Modified: Wed Apr 14, 1999