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The multidisciplinary U.S. Geological Survey (USGS) Tampa Bay Study has released a new "topobathymetric" map that merges topographic (land elevation) and bathymetric (water depth) data into a high-resolution image of Florida's Tampa Bay and adjacent watersheds (URL http://pubs.usgs.gov/of/2007/1051/). With a spatial resolution of approximately 3 meters, this topobathymetric map is the highest resolution map of its type for this large estuarine system.
The map grew out of the acquisition of high-resolution bathymetric data from various sites in Tampa Bay to support the development of hydrodynamic and sediment-transport models. The map's first author, Dean Tyler of the USGS Center for Earth Resources Observation and Science (EROS), created the map by merging the disparate datasets. All of the topographic data come from the USGS National Elevation Dataset (NED) and much of the bathymetric data from NOAA's GEOphysical DAta System (GEODAS). For most of the nearshore areas around the bay, GEODAS data were replaced with higher-resolution bathymetric data acquired in 2003 and 2004 with the National Aeronautics and Space Administration (NASA) Experimental Advanced Airborne Research Lidar (EAARL).
Lidar, an acronym for light detection and ranging, is an optical technique for accurately and quickly measuring distance with lasers. The basic principle is to emit a short pulse of laser light and record the time it takes for the light to reflect off a distant object and return to the starting point. When installed in an airplane and pointed downward, lidar systems can be used to measure topography and nearshore bathymetry. Water clarity determines how deep the laser light can penetrate; under ideal conditions, the maximum water depth of EAARL data points is roughly 25 m. In the new Tampa Bay map, EAARL depth measurements extend down to approximately 3 m. The EAARL system is flown in a Cessna-type aircraft at a nominal altitude of 300 m. As the aircraft moves forward, EAARL sweeps a series of laser pulses at 2-m intervals from left to right along a swath line 240 m long. Each pulse represents a unique distance measurement, and 25 swath lines are covered every second. The new map has unprecedented resolution in the areas where EAARL data have been collected.
Tampa Bay is one of several areas in the United States for which the USGS EROS data center has merged topographic and bathymetric datasets. Visit URL http://gisdata.usgs.net/website/TopoBathy/ to view and download merged datasets for parts of Puget Sound, Delaware Bay, and the San Francisco Bay region, as well as Tampa Bay.
Now in its final year, the Tampa Bay Study is a USGS-led 5-year effort conducted in partnership with other Federal, State, academic, and local partners (see URL http://gulfsci.usgs.gov/tampabay/). Participants used an integrated science approach to study relations between geologic, biologic, chemical, and hydrologic components of the Tampa Bay estuarine system. This technique provides scientists and managers with tools to measure the impacts of changes, both natural and anthropogenic, on all components of estuarine systems. Results from this research will enable scientists and resource managers to better assess management strategies and guide future policy.
The new topobathymetric map is the Tampa Bay Study's latest data product; its full citation is:
Tyler, Dean, Zawada, D.G., Nayegandhi, Amar, Brock, J.C., Crane, M.P., Yates, K.K., and Smith, K.E.L., 2007, Topobathymetric data for Tampa Bay, Florida: U.S. Geological Survey Open-File Report 2007-1051 [URL http://pubs.usgs.gov/of/2007/1051/].
in this issue:
High-Resolution Map Merges Tampa Bay Bathymetry and Topography
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