Michael Sartori

Airborne laser swath mapping shines new light on Earth's topography

Airborne Laser Swath Mapping (ALSM) now makes it possible to delineate the physical features of the surface of Earth on spatial scales as fine as a few decimeters horizontally and a few centimeters vertically As a result, Earth scientists may finally be able to answer long-standing scientific questions about such surficial processes as erosion, faulting, volcanism, and plate motion. Information on surface relief, drainage patterns, and vegetation, critical to understanding the evolution of ecologically sensitive areas, can be collected over hundreds of square kilometers in a period of days. Information collected by ALSM can also be used to address a wide variety of engineering issues, such as developing and managing natural resources7semi; mitigating the impacts of such natural disasters as floods, hurricanes, tornados, landslides, and sinkholes; and building and maintaining transportation infrastructure.

Capability Assessment and Performance Metrics for the Titan Multispectral Mapping Lidar

In this paper we present a description of a new multispectral airborne mapping light detection and ranging (lidar) along with performance results obtained from two years of data collection and test campaigns. The Titan multiwave lidar is manufactured by Teledyne Optech Inc. (Toronto, ON, Canada) and emits laser pulses in the 1550, 1064 and 532 nm wavelengths simultaneously through a single oscillating mirror scanner at pulse repetition frequencies (PRF) that range from 50 to 300 kHz per wavelength (max combined PRF of 900 kHz). The Titan system can perform simultaneous mapping in terrestrial and very shallow water environments and its multispectral capability enables new applications, such as the production of false color active imagery derived from the lidar return intensities and the automated classification of target and land covers. Field tests and mapping projects performed over the past two years demonstrate capabilities to classify five land covers in urban environments with an accuracy of 90%, map bathymetry under more than 15 m of water, and map thick vegetation canopies at sub-meter vertical resolutions. In addition to its multispectral and performance characteristics, the Titan system is designed with several redundancies and diversity schemes that have proven to be beneficial for both operations and the improvement of data quality.

Control methods for merging ALSM and ground-based laser point clouds acquired under forest canopies

Merging of point data acquired from ground-based and airborne scanning laser rangers has been demonstrated for cases in which a common set of targets can be readily located in both data sets. However, direct merging of point data was not generally possible if the two data sets did not share common targets. This is often the case for ranging measurements acquired in forest canopies, where airborne systems image the canopy crowns well, but receive a relatively sparse set of points from the ground and understory. Conversely, ground-based scans of the understory do not generally sample the upper canopy. An experiment was conducted to establish a viable procedure for acquiring and georeferencing laser ranging data underneath a forest canopy. Once georeferenced, the ground-based data points can be merged with airborne points even in cases where no natural targets are common to both data sets. Two ground-based laser scans are merged and georeferenced with a final absolute error in the target locations of less than 10cm. This is comparable to the accuracy of the georeferenced airborne data. Thus, merging of the georeferenced ground-based and airborne data should be feasible. The motivation for this investigation is to facilitate a thorough characterization of airborne laser ranging phenomenology over forested terrain as a function of vertical location in the canopy.