Coastal Single-beam Bathymetry Data Collected in September and October 2019 from Rockaway Peninsula, New York

GPS Acquisition: Two Global Positioning System (GPS) base stations were established near the survey area. The primary base station, RIIS, is a USGS installed P/K nail located in the dockage area of the former Riis Landing U.S. Coast Guard Station located just west of the Marine Parkway Bridge on the Rockaway Peninsula. The secondary station, FLYD, was an additional USGS installed P/K nail located on the retired airstrip of Floyd Bennett Field, located in southeast Brooklyn, New York City. The base stations were continually occupied and equipped with a Spectra Precision SP90M (RIIS) and a Spectra Precision Proflex 800 (FLYD) GPS receiver recording full-carrier-phase positioning signals (L1/L2) from satellites via Thales Choke-ring antennas, recording at a rate of 0.1 s.

Single-Beam Bathymetry Acquisition: The single-beam bathymetric data were collected under USGS FAN 2019-333-FA, which encompass data from three separate survey platforms; The R/V Shark (19CCT05), a 12-ft Yamaha PWC collected 94.73 line-km (84 lines), the R/V Chum (19CCT06), an additional 12-ft Yamaha PWC collected 94.86 line-km (83 lines), and a seismic sled towed by the R/V Sallenger (sled FAN 19CCT07) collected 210.17 line-km (73 lines). A total of 399.76 line-km (240 lines) were surveyed. Boat motion was recorded at 50-millisecond (ms) intervals using an SBG motion sensor. HYPACK (version 18.1.8.0), a marine surveying, positioning, and navigation software package, managed the planned-transect information and provided real-time navigation, steering, correction, data quality parameters, and instrumentation-status information to the vessel operator. Depth soundings were recorded at 50-ms intervals using an Odom Echotrac CV100 sounder with a 4 degree, 200-kilohertz (kHz) transducer. Data from the GPS receiver, motion sensor, and fathometer were recorded in real-time aboard the platform independently and merged into a single raw data file (*.RAW) in HYPACK, with each device string referenced by a device identification code and time stamped to Coordinated Universal Time (UTC). Sound velocity profile (SVP) measurements were collected using three separate SonTek Castaway conductivity, temperature, and depth (CTD) instruments deployed from each survey platform. The instruments were periodically cast overboard to observe changes in water column speed of sound (SOS). A total of 49 successful sound velocity casts were taken throughout the survey at an average depth of 3.13 m, and on average produced a sound velocity of 1514.25 meters per second (m/s).

Differentially Corrected Navigation Processing: The coordinate value of the GPS base station is the time weighted average (TWA) of all current survey occupations. The base station coordinates were imported into GrafNav version 8.7 and the kinematic GPS data from the survey platform were post-processed to the concurrent GPS session data at the base station. During processing, steps were taken to ensure that the trajectories between the base and the rover were clean, resulting in fixed positions. By analyzing the graphs, trajectory maps, and processing logs that GrafNav produces for each GPS session, GPS data from satellites flagged by the program as having poor health or satellite time segments that had cycle slips could be excluded, or the satellite elevation mask angle could be adjusted to improve the position solutions. The final differentially corrected, precise DGPS positions were computed at 0.1 s and exported in American Standard Code for Information Interchange (ASCII) text format. In subsequent processing steps, these data will replace the uncorrected, real-time rover positions. The GPS data were processed and exported in the WGS84 (G1762) geodetic datum.

Single-beam Bathymetry Processing: All data were processed using CARIS HIPS and SIPS (Hydrographic Information Processing System and Sonar Information Processing System) version 11.3.4. The raw HYPACK data files were imported into CARIS, the differentially corrected navigation files were imported using the generic data parser (GDP) tool, and any SVP profile casts were entered and edited using the SVP editor. The bathymetric data components (position, motion, depth, and SOS) for all data were then merged and geometrically corrected in CARIS to produce processed x,y,z data. Next, the data were edited for outliers and then further reviewed in the Subset Editor utility for crossing status, and questionable data points or areas. The geometrically corrected point data were then exported as an x,y,z ASCII text file referenced to WGS84 (G1762), ellipsoid height in meters.

Quality Control, Quality Assurance (QA/QC): All single-beam data exported from CARIS were imported into Esri ArcMap version 10.6.0, where a shapefile of the individual sounding data points (xyz) was created and plotted in 0.25-m color coded intervals. First, all data were visually scanned for any obvious outliers or problems. Next, a track line shapefile was produced using X-tools Pro "Make Polylines from Points" function. Utilizing both the x,y,z (point) and track line (polyline) shapefiles, an in-house Python script evaluated elevation differences at the intersection of crossing track lines by calculating the elevation difference between points at each intersection using an inverse distance weighting equation with a search radius of 1 m. The calculated RMS errors when a vessel crosses a track line previously surveyed is as follows: WVR1 (19CCT05) = 7.1 cm, WRV2 (19CCT06) = 8.30 cm, and the Sled (19CCT07) = 5.1 cm, respectively. Once individual platform statistics were obtained, all x,y,z data were merged into a single shapefile and a crossing analysis preformed, which yielded an 8.16 cm RMS error. Since the bias between the platform elevations was on the order of the Odom instrument accuracy (1 cm +/- 0.7 percent depth), no adjustments were made. The merged file was exported from Esri ArcMap as an x,y,z text (.txt) file and made available in the download section of this data release, along with the populated track line shapefiles.

Datum Transformation: NOAA's VDatum v.4.1 was used to transform single-beam data points (x,y,z) from their acquisition datum WGS84 (G1762) to the NAD83 (horizontal), and the NAVD88 (vertical) reference frames using the NGS geoid model of 2012B (GEOID12B). For conversion from the WGS84 ellipsoid to NAVD88, there is a total of 7.616 cm of uncertainty in the transformation (https://vdatum.noaa.gov/docs/est_uncertainties.html). Resultant data files have been made available in the downloads section of this data release.

Added keywords section with USGS persistent identifier as theme keyword.