Summary

Description

Bathymetry for Tomales Bay was derived from three surveys containing22,020 soundings. Five older, less accurate, overlapping surveys wereomitted before tinning. The average separation between soundings was 37meters. The three surveys used dated from 1993 and 1994. The total range ofsounding data was 1.5 meters to -18.9 meters at mean low water. A mean highwater value of 1.1 meters was assigned to the shoreline. Two points were foundthat were not consistent with the surrounding data and were removed priorto tinning. DEM grid values outside the shoreline (on land) wereassigned null values (-32676).Tomales Bay has four 7.5 minute DEMs and a single one degree DEM. The1 degree DEMs were generated from the higher resolution 7.5 minuteDEMs which covered the estuary. A Digital Elevation Model (DEM)contains a series of elevations ordered from south to north with theorder of the columns from west to east. The DEM is formatted as oneASCII header record (A- record), followed by a series of profilerecords (B- records) each of which include a short B-record headerfollowed by a series of ASCII integer elevations (typically in unitsof 1 centimeter) per each profile. The last physical record of theDEM is an accuracy record (C-record).The 7.5-minute DEM (30- by 30-m data spacing) is cast on theUniversal Transverse Mercator (UTM) projection. It provides coveragein 7.5- by 7.5-minute blocks. Each product provides the samecoverage as a standard USGS 7.5-minute quadrangle but the DEMcontains over edge data. Coverage is available for many estuaries ofthe contiguous United States but is not complete.