Single-Beam Bathymetry of the Hurricane Sandy Breach at Fire Island, New York, June 2013 (1-Meter Digital Elevation Model)

Single-beam data were collected in the Atlantic Ocean (offshore of Fire Island, NY), through the breached area and in Great South Bay (near Pelican Island, NY) onboard the USACE's LARC-5 amphibious vehicle. The LARC operator used the RTK GPS to follow a pre-defined course of survey lines entered into HYPACK, prior to the start of the survey. The Trimble 4000 RTK GPS software combined with HYPACK 2013 Hydrographic survey software helped ensure the operator stayed on course throughout data acquisition.

HYPACK software was used to merge the GPS and echosounder data to create text files, in .RAW format, which were later analyzed by the custom-built USACE Field Research Facility FORTRAN software. Conductivity, temperature and depth (CTD) were measured at the beginning of the survey (at the -8m isobath) and at the end of the survey (at the -8m isobath) aboard the LARC to determine the speed of sound in the water column. The time-stamp on the echosounder was corrected for 'drift' using the GPS time clock. The custom FRF software was used to remove the motion of the LARC due to waves and changing tide level. It also adjusted the measurements to changes in the speed of sound over the survey area and correctly aligned the time of the echosounder and the GPS data. This was done by dynamically adjusting the time or latency of the GPS data relative to the echosounder data until a best fit was achieved.

Land points were separated from points in the water by first computing the average and standard deviation for all GPS elevations collected when the echosounder data indicated that the LARC was floating.

Post-processed topographic-bathymetric data from USACE were importedinto ArcGIS 10.2.1, converted to a NAD 1983 UTM Zone 18N coordinate system, saved as a point shapefile and used to create a trackline map of the single-beam point data coverage. Errant data points were manually removed from the data. The edited trackline data were exported from ArcGIS into a text file as well as being used to create a 32 bit raster grid and calculate vertical RMSE; the grid was computed using a natural neighbors gridding algorithm with a 1-m grid cell. The raster grid was also used to generate a color-contoured image of the breach.

Added keywords section with USGS persistent identifier as theme keyword.