Summary

Description

Bathymetry for Atchafalaya Bay was derived from eleven surveys containing127,192 soundings. No surveys were omitted. The average separationbetween soundings was 130 meters. The surveys dated from 1934 and 1935. Therange of soundings for the eleven surveys was 0.9 meters to -39.0 metersat mean low water. Mean high water values between 0.4 and 0.6 meters wereassigned to the shoreline. Twelve points from three surveys were foundthat were not consistent with the surrounding data. These points wereremoved prior to tinning. DEM grid values outside the shoreline (onland) were assigned null values (-32676).Atchafalaya Bay has twenty-six 7.5 minute DEMs and a single onedegree DEM. The 1 degree DEMs were generated from the higherresolution 7.5 minute DEMs which covered the estuary. A DigitalElevation Model (DEM) contains a series of elevations ordered fromsouth to north with the order of the columns from west to east. TheDEM is formatted as one ASCII header record (A- record), followed bya series of profile records (B- records) each of which include ashort B-record header followed by a series of ASCII integerelevations (typically in units of 1 centimeter) per each profile.The last physical record of the DEM 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.