Casco Bay, ME (N100) Bathymetric Digital Elevation Model (30meter resolution) Derived From Source Hydrographic Survey SoundingsCollected by NOAA

Bathymetry for Casco Bay was derived from fourteen surveys containing297,004 soundings. No surveys were omitted. The average separationbetween soundings was 38 meters. The surveys dated from 1941 to 1946. Thetotal range of sounding data was 2.1 meters to -73.2 meters at mean lowwater. Mean high water values of 2.7 or 2.8 meters were assigned to theshoreline. Thirty-one points were found that were not consistent with thesurrounding data. These were removed prior to tinning. DEM grid values outside the shoreline (on land) were assigned null values (-32676).Casco Bay has twelve 7.5 minute DEMs and two one degree DEMs. The 1degree DEMs were generated from the higher resolution 7.5 minute DEMswhich covered the estuary. A Digital Elevation Model (DEM) contains aseries of elevations ordered from south to north with the order ofthe columns from west to east. The DEM is formatted as one ASCIIheader record (A- record), followed by a series of profile records(B- records) each of which include a short B-record header followedby a series of ASCII integer elevations (typically in units of 1centimeter) per each profile. The last physical record of the DEM isan 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.