SHOALS Toolbox: Software to Support Visualization and Analysis of Large, High-Density Data Sets

摘要

The Coastal and Hydraulics Engineering Technical Note (CHETN) described herein outlines the capabilities of SHOALS Toolbox, a stand-alone software package designed to facilitate the use of SHOALS (Scanning Hydrographic Operational Airborne Lidar Survey) and other high-density survey data in engineering analyses. The SHOALS Toolbox comprises a suite of tools with which to visualize, manipulate, and analyze SHOALS data, in keeping with current U.S. Army Corps of Engineers (USACE) computer and engineering analysis standards. The SHOALS Toolbox is available free to all USACE elements and their contractors. SHOALS is an airborne laser system that makes water-depth soundings (Figure 1). The laser is collimated red (1,064 nanometers nm) and green (532 nm) light pulsed at a rate of 400 Hz. A scanning mirror directs each laser pulse toward the sea surface and into the forward flight path of the aircraft. Receivers in the aircraft detect the return of each pulse from the sea surface ('specular interface reflection,' Figure 2) and sea floor ('diffuse bottom reflection' and 'reflected bottom signal,' Figure 2). These returns are analyzed to determine water depth or land elevation for each laser pulse. Each measurement is geo-positioned using either pseudo-range or carrier-phase GPS techniques. The result is an XYZ data set containing measurements spaced approximately 4-8 m apart and covering nearshore land elevations through water depths as great as 60 m.