NCCOS Mapping: Geospatial products of water depth, acoustic backscatter, and ROV data collected from NOAA Ship Nancy Foster in the Dry Tortugas, Florida Keys National Marine Sanctuary from 2021-03-18 to 2021-04-10 (NCEI Accession 0290189)

Methods:
This survey was conducted from the NOAA Ship Nancy Foster and using the complete coverage MBES specification as defined in the Hydrographic Survey Specifications and Deliverables (HSSD). Prior to data collection at the Areas of Interest (AOI), static drafts were measured and confirmed with the SIS/HVF and a patch test was performed on both MBES systems on DN079. While conducting the survey bathymetric coverage was monitored by creating CUBE surfaces with 2m resolutions as per the HSSD. Sounding densities generally meet the 95% of all nodes population criteria. The Nancy Foster is outfitted with an Applanix POS/MV 320 Version 5 GNSS inertial system. The POS/MV was used to measure attitude, heading, heave, and position for the MBES system. The POS/MV consists of an Inertial Motion Unit (IMU), two dual frequency GNSS antennas and a topside control unit. The POS/ MV is augmented in real time with Fugro Marinestar SBAS Satellite service which improves the POS/MV positional accuracies to sub-DGPS standards. The POS/MV position, timing, heading and motion data were output to the Hypack and SIS acquisition systems using the POS/MV real-time ethernet option at 25 Hz. Additionally, using ethernet and USB logging controls, the POS/MV was configured to log TrueHeave™ and all of the raw observable groups needed to post process real-time navigation data. The POS/MV logged 13 megabyte files, which resulted in multiple files created per day. The POS/MV onboard incurred intermittent dropouts that made several *.all files to have no ellipsoidal heights embedded within the navigation data. The days/lines that were affected were DN082/0134-139 and DN098/644 and DN100/0744. Attempts were made using POSpac SBETs and reapplication of GPS Heights with the *.000 files to salvage these lines. The results were unsuccessful and it was determined that the TCARI and ZDF solutions created more vertical error than just applying a zero tide file. Corrected Heights were obtained by utilizing an ellipsoid referenced separation model with separations derived from the NAD83/GRS80 ellipsoid to MLLW utilizing VDATUM and Geoid12b. This separation model was applied to the realtime POS/MV Fugro Marinestar SBAS navigation and delivers published accuracies in the 10cm range. Due to the remote location of the FKNMS AOI, CORS station corrections were not available to produce PPK SBETs for post-processed navigation. Zoned Tides were also not sufficient for processing due to the large distances from the nearest two tide stations in Key West and Naples, Florida. Additionally, TrueHeave files were applied to the Nancy Foster MBES data to improve vessel attitude correctors. All acquisition and processing workstations are located in the Dry Lab of the Nancy Foster, are networked as a workgroup, and are interfaced with the ship’s backup system. Xylem Hypack 2020 was used for vessel navigation. Kongsberg Seafloor Information System (SIS) software was used to acquire the bathymetric data in the .all format. Bathymetric survey data was converted and processed in Caris HIPS with modifications to the default Combined Uncertainty Bathymetric Estimator (CUBE) Parameters XML file. The default CUBE Parameters XML was replaced with the XML file issued to 5 W00603 NOAA Ship Nancy Foster (R352) all NOAA hydrographic field units included with the Field Procedures Manual. This updated XML file uses the resolution dependent maximum propagation distance values required in the HSSD. Processing methodology followed the standard Caris HIPS CUBE workflow. These steps include data conversion using HSTB supplied HVF files for each MBES system, filtering, TrueHeave application, GPS tide correction (VDATUM Separation Model), Total Propagated Uncertainty (TPU) calculation, merging, and swath/subset editing. Acoustic backscatter was collected with both Kongsberg systems for benthic habitat delineation and chart creation. The Marine Spatial Ecology Division processed backscatter in Fledermaus Geocoder Toolbox (FMGT).

File Information:
Total File Size: 49.6 GB total, 18 files in 4 folders (unzipped), 759 MB (zipped)

Data File Format(s):
Tiff and ShapeFile

Data File Compression: zip

Data File Resolution: Bathymetry 1x1m
Backscatter 1x1m
GIS Projection: Geographic Coordinate System: NAD 1983 (WKID 4269); Projected Coordinate System: NAD 1983 UTM Zone 17N (WKID 26917) & NAD 1983 UTM Zone 17N (WKID 32617)