The Plate Boundary Observatories includes a geodetic component known as GeoEarthScope, an initiative to obtain Airborne LiDAR Imagery, Satellite InSAR Imagery, and geochronologic data. MREFC activities condluded successfully on September 30, 2008.
LiDAR (Light Detection and Ranging) uses laser light to measure distances. Airborne laser-scanning technology is a specialized, aircraft-based type of lidar that provides extremely accurate, detailed 3-D measurements of the ground, vegetation, and buildings. In airborne-laser-mapping lidar, lasers are taken into the sky. Instruments are mounted on a single- or twin-engine plane or a helicopter. Airborne lidar technology uses four major pieces of equipment.
These are a laser emitter-receiver scanning unit attached to the aircraft; global positioning system (GPS) units on the aircraft and on the ground; an inertial measurement unit (IMU) attached to the scanner, which measures roll, pitch, and yaw of the aircraft; and a computer to control the system and store data. The laser scanner on the aircraft sends up to 100,000 pulses of light per second to the ground and measures how long it takes each pulse to reflect back to the unit. These times are used to compute the distance each pulse traveled from scanner to ground.
The GPS and IMU units determine the precise location and attitude of the laser scanner as the pulses are emitted, and an exact coordinate is calculated for each point. The laser scanner uses an oscillating mirror or rotating prism (depending on the sensor model), so that the light pulses sweep across a swath of landscape below the aircraft. Large areas are surveyed with a series of parallel flight lines.
Data acquisition campaigns took place in 2007 and 2008 and cover a total area of nearly 5,000 km2. General maps of GeoES LiDAR coverage are available here. Google Earth files showing detailed coverage by target region are available here. All NoCal data are processed and available as Google Earth hill-shade files or ARC binary DEM files from OpenTopography.org. Data from other regions are currently being processed and will become available soon.
InSAR (Interferometric Synthetic Aperture Radar) data suitable for interferometric analyses were ordered from data provider catalogs, spanning the period from 1992-2008 and covering all of the western U.S. as well as parts of Alaska, Hawaii, and regions in the eastern and southern U.S. The GeoES catalog currently contains ~16 TB of SAR data with several more TB's expected to be delivered soon. More details, including data access procedures, are available at geoes-insar.unavco.org.
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National Aeronautics and |
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National |
Overview
2010