Terrestrial-Based Lidar Beach Topography of Fire Island, New York, June 2014

Equipment

The mobile T-lidar system used by the USGS LMG WSC includes an Optech ILRIS HD-ER-MC instrument in conjunction with an Applanix position and orientation system (POS MV) (fig. 3). The Optech ILRIS HD-ER-MC has a laser repetition rate of 10 kilohertz and a laser wavelength of 1,535 nanometers, which lies within the near-infrared portion of the electromagnetic spectrum. The POS MV consists of two global positioning system (GPS) receivers, an inertial measurement unit (IMU), and a position and orientation computer.

The mobile T-lidar system requires a rigorous calibration procedure before accurate datasets can be generated. All instrumentation must first be surveyed, and their relative positions (lever arms) must be resolved with respect to the origin point of the IMU. Next, a boresight procedure was performed in order to determine the angular differences (roll, pitch, and heading) between the IMU and the T-lidar instrument.

Figure 3. The U.S. Geological Survey Lower Mississippi-Gulf Water Science Center T-lidar survey vehicle used at Fire Island, New York, to collect beach elevation data. The T-lidar scanner (larger yellow box) is positioned above the roofline and is shown facing the rear of the vehicle. The POS MV IMU (smaller yellow box) is positioned directly beside the T-lidar scanner to best capture changes in scanner orientation. Dual GPS antennas (white discs) are mounted on the rear corners of the truck bed. [larger version]