Chesapeake Bay SAV data were mapped from aerial imagery, primarily at a scale of 1:24,000, for the
following regions: western shore, Va. only - 1971 & 1974; lower Bay, Va.
only - 1980 & 1981; upper Bay, selected sections, 1979; Baywide, 1978, 1984
- 1987, and 1989 - 2016. Each area of SAV was classified into one of four
density classes by the percentage of cover as determined from the aerial
imagery (methodology is described in each annual report - e.g. see Orth et al., 2016). Starting in 2010, the SAV beds are stored
as ArcGIS shapefiles using the quality control procedures documented in
the individual metadata files. Data for prior years are stored as ArcInfo
GIS coverages. Data were collected by the Virginia Institute of Marine
Science and can be attributed by including a reference to the associated
annual SAV distribution and abundance report.
The SAV data files for years prior to 2010 are in uncompressed ArcInfo (ESRI, Redlands, CA)
export format. They have been compressed using pkzip compression to form .zip
files for use on Windows-compatible personal computers and also compressed using
unix standard compression to form .tar.Z files for use on unix platforms. Each
file contains both the .e00 ARC/INFO export file and also a .txt metadata file.
Starting in 2010, the .zip file contains a shapefile and metadata xml file.
Please consult the metadata file to determine if a particular dataset will
satisfy your needs.