RIEGL VQ-820-G in Operation: Seagrass Overview
On March 5 and 6, 2013, RIEGL USA, in collaboration with Aerial Cartographics of America (ACA), carried out a test of the RIEGL VQ-820-G bathymetric airborne laser scanning system over Tampa, Florida. The purpose of this trip was to determine the ability of the VQ-820-G to identify submerged aquatic vegetation mapping. This data was presented to scientists with the South Florida Water Management District (SFWMD) to analyze the wealth of information this LiDAR system produces.
The bathymetric data collect took place over the course of three days over sites in the Tampa Bay area. Two sites were located in Clearwater Florida in the north side of Tampa. The other three sites were located in Sarasota Florida just south of Tampa.
The VQ-820-G was mounted on ACA’s Cessna 208 Caravan for the five test flights flown over Tampa, Florida and for the boresight calibration flight over Poinciana, Florida. The sites were flown at 600m AGL at 100 knots. The wind and water conditions during the flights allowed for 4m water penetration in these intercostal and river mouth regions under analysis.
The VQ-820-G excelled in shallow water areas where previously, detailed mapping had not been possible. Deeper regions in the center of river beds and in the ocean have been accurately mapped with other technology but they were not able to map shallow regions. The VQ-820-G solves this problem with a high point density akin to topographic scanners and the ability to record full wave returns in this region. This RIEGL scanner system fills the gap that current bathymetric technology systems such as multi-beam sonar systems, side scan sonar system and other bathymetric LiDAR systems lack in performance.
The multiple target capability of this scanner is what makes this such a powerful tool for shallow water bathymetric mapping. The data presented to the SFWMD clearly showed the scanners ability to discern between water surface, bottom, and returns from vegetation.
The Riegl software suite was a key element in this solution due to its ability to calibrate, acquire, process, geo-reference and export.
The scientists at the SFWMD were very pleased with the quality of the data that the VQ-820-G acquired. Observations on the growth of algae and seagrass in the shallow water regions are of high importance to them in the field of Benthic Mapping. The health of the seagrass and algae in these regions can be tracked, based off the density of the vegetation and over time, due to the ability to acquire and process data quickly with the RIEGL VQ-820-G. This type of monitoring was previously not possible unless they physically took samples of a small region. This technology provides the potential for the SFWMD to scale up their monitoring of shallow water vegetation.
This case study of scanning vegetation in shallow water regions adds Benthic Mapping to the long list of applications of the RIEGL VQ-820-G which include river bed profiling, coastline and shallow water mapping, habitat mapping, acquiring base data for flood prevention, measurement for aggradation zones, monitoring of hydraulics laboratories, surveying for hydraulic engineering, and hydro-archaeological surveying.