GIS Data Layers

The GIS data files are grouped by the themes described in this section. Each theme is a subdirectory under 'data', 'exp_arc', and 'shape', though there may not be files in all directories.

BASEMAPS

Basemap data layers include coastline, sanctuary boundaries, place names, and geographic graticules assembled from published sources where available and from digital files produced in-house.

BATTOPO

Bathymetry and topography data files include contour coverages and grids. The grids have resolutions from 250 m for the largest area to 5m for selected smaller data windows.

SHADEREL

Gray shaded-relief TIFF images are based on elevation grids in BATTOPO.

NAVIGATN

Location data in the form of navigation tracklines, one-minute time fixes (where available) and instrument locations are provided for each of the cruises during which data were collected during this project. Instrument packages have been set out at several locations along the shelf and Monterey Canyon to record currents, turbidity, sediment accumulation, hydrostatic pressure, salinity, temperature, and water depth. These instruments provide information about changes over the deployment periods of August 1997 to August 1998 (Xu and others, 2002).

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BACKSCAT

Sidescan sonar imaging provides high-resolution images of the sea floor by recording the intensity of sound backscattered off the sea floor. A total of 7000 line-km (4400 mi) of sidescan imagery and companion sub-bottom seismic-reflection data were collected by the USGS and cooperators between 1995 and 1998 in the shelf areas between Point Ano Nuevo and Point Sur. South of Monterey Canyon and Moss Landing, multibeam systems were used that provided high-resolution bathymetry as well as sidescan sonar. The sidescan data have been processed and mosaicked into a continuous image of 1,200 sq km (460 sq mi) of the sea floor. The sidescan GIS data layer is an image built from data with a horizontal resolution between 40 cm and 2.5 m (16 in to 8 ft) with grayscale values proportional to the sonar backscatter of the sea floor (Chavez and others, 1998, 2002). For ease of viewing and storage space, the sidescan data have been divided into panels bound by 7.5-minute quadrangles.

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