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by Helen Gibbons

A newly acquired terrestrial lidar (light detection and ranging) scanner was the focus of training at the U.S. Geological Survey (USGS) Pacific Coastal and Marine Science Center in Santa Cruz, California, in December 2012. USGS technicians and scientists learned how to operate the new instrument during a 4-day workshop organized by Deputy Center Director for Marine Operations George Tate and geographer Joshua Logan.

Lidar scanners use laser light to measure distances, producing highly accurate three-dimensional maps and images of terrain. USGS scientists make extensive use of lidar to study landscape change, employing both airborne lidar scanners (for example, see lidar maps of coastal change caused by Hurricane Sandy) and ground-based lidar scanners (read about ground-based lidar to track rapid coastal change in USGS Fact Sheet 2006–3111).

The newly acquired scanner—a RIEGL VZ-1000—is a ground-based unit that can be mounted on a tripod for surveying coastal terrain from positions on land or mounted on a moving platform, such as a boat or car, for conducting surveys while underway.

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Riegl USA representative Bret Bienkowski taught the December workshop, beginning with an introduction to the lidar scanner and its software. On the second day of the training, participants took the instrument into the field, scanning terrain at Younger Lagoon, about 1 mile southwest of the Pacific Coastal and Marine Science Center, for comparison with data from previous surveys. The rest of the workshop focused on post-processing, data flow, and data management.

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The addition of the scanner to the Pacific Coastal and Marine Science Center instrument pool will complement existing lidar capabilities. The instrument will not only save the center considerable equipment-rental expenses in future work but also provide additional capabilities important to center scientists, such as:

• The ability to scan from a moving vessel, allowing center personnel to conduct topographic surveys concurrently with bathymetric surveys and thus collect co-registered elevation data from coastal land and adjacent seafloor. (Read about such mapping tested by the USGS in the Gulf of Mexico in July 2011, USGS Scientists Develop System for Simultaneous Measurements of Topography and Bathymetry in Coastal Environments.)
• The ability to detect and record "multiple returns" for each laser pulse emitted. When the laser light reflects off multiple objects (for example, several pieces of vegetation and the ground behind it), the scanner can record the location of each object. Processing software can distinguish between these multiple returns, which can assist in filtering out vegetation data from ground-surface data.
• The ability to collect geographically registered data sets by using a Geographic Positioning System (GPS) interface, a built-in electronic compass, and an inclinometer.

The first scientific use of the new lidar scanner will likely be continued surveying along the Elwha River to document the changes caused by dam removal. Stay tuned!