Bathymetry--Offshore of Coal Oil Point, California

During the CSUMB and Fugro Pelagos multibeam mapping missions, an Applanix POS MV (Position and Orientation System for Marine Vessels) was used to accurately position the vessels during data collection, and it also accounted for vessel motion such as heave, pitch, and roll (position accuracy, +/-2 m; pitch, roll, and heading accuracy, +/-0.02 degrees; heave accuracy, +/-5 percent, or 5 cm). To account for tidal-cycle fluctuations, CSUMB used NavCom 2050 GPS receiver (CNAV) data, and Fugro Pelagos used KGPS data (GPS data with real-time kinematic corrections). In addition, sound-velocity profiles were collected with an Applied Microsystems (AM) SVPlus sound velocimeter. Soundings were corrected for vessel motion using the Applanix POS MV data, for variations in water-column sound velocity using the AM SVPlus data, and for variations in water height (tides) using vertical-position data from the CNAV receiver and the KGPS data. Most soundings were converted to 2-m-resolution bathymetric-surface-model grids; however, soundings along the outer shelf and slope in water depths greater than 80 m were converted to a 5-m-resolution bathymetric-surface-model grid because of lower sounding density. Final 2007 XYZ soundings and bathymetric-surface models were referenced to the World Geodetic System of 1984 (WGS 1984) relative to the North American Vertical Datum of 1988 (NAVD 1988); the 2008 soundings were referenced to the North American Datum of 1983 (NAD 1983) relative to NAVD 1988. During the USGS mapping missions, differential GPS (DGPS) data (2006, 2007) and GPS data with real-time kinematic corrections (2008) were combined with measurements of vessel motion (heave, pitch, and roll) in a CodaOctopus F180 attitude-and-position system to produce a high-precision vessel-attitude packet. This packet was transmitted to the acquisition software in real time and combined with instantaneous sound-velocity measurements at the transducer head before each ping. The returned samples were projected to the seafloor using a ray-tracing algorithm that works with previously measured sound-velocity profiles. Statistical filters were applied to discriminate seafloor returns (soundings) from unintended targets in the water column. The original 2006 and 2007 soundings were referenced to the WGS 1984 relative to the MLLW (Mean Lower Low Water) tidal datum, but, through postprocessing using NOAA's VDatum tool, the soundings were transformed to NAVD 1988. The original 2008 soundings were referenced to the North American Datum of 1983 (NAD 1983), relative to NAVD 1988. Finally, the soundings were converted into 2-m-resolution bathymetric-surface-model grids. During the Fugro Pelagos coastal airborne-lidar mapping mission that was completed as part of the National Coastal Mapping Program of USACE, the Leica ALS60 topographic-lidar and the SHOALS-1000T bathymetric-lidar systems were mounted on an aircraft that flew survey lines at an altitude of 300 to 400 m (bathymetry) and 300 to 1,200 m (topography), at speeds of between 135 and 185 knots. The ALS60 system collected data at a maximum pulse rate of 200 kHz, and the SHOALS system collected data at 1 kHz. Information on aircraft position, velocity, and acceleration were collected using the Novatel and POS A/V 410 systems (SHOALS) and the onboard GPS/IMU system (ALS60). Aircraft-position data were processed using POSPac software, and the results were combined with the lidar data to produce 3-D positions for each lidar shot. Various commercial and proprietary software packages were used to clean the data, to convert all valid data from ellipsoid to orthometric heights, and to export the data as a series of topography and bathymetry ASCII files. Final grids were provided in geographic coordinates referenced to the NAVD 1988.

California State University, Monterey Bay, Seafloor Mapping Lab and Fugro Pelagos 2-m and 5-m-resolution bathymetry data within this map were downloaded from http://seafloor.csumb.edu/SFMLwebDATA.htm

USGS 2-m-resolution bathymetry data from mapping cruises Z-2-06-SC, Z-1-07-SC, and S-0-08-SC were downloaded from USGS archives.

Topographic - Bathymetric lidar data were provided to the USGS, PCMSC by USACE.

Transform all bathymetry data to common projection, datum, and UTM zone. Merge all 2-m bathymetry data into 2-m-resolution bathymetry grid and clip to the Offshore of Coal Oil Point, California, map boundary. 5-m resolution bathymetry grid was processed as separate grid.

Added Distribution_Information section to metadata to facilitate data download.

Keywords section of metadata optimized for discovery in USGS Coastal and Marine Geology Data Catalog.

Added keywords from Coastal and Marine Ecological Classification Standard (CMECS) to metadata.

Edited metadata to add keywords section with USGS persistent identifier as theme keyword. No data were changed.

Performed minor edits to the metadata to correct typos. No data were changed

Metadata was modified to bring up to current USGS PCMSC standards. USGS Thesaurus and keywords were added, information for accompanying Open-File Report added to Abstract and Cross Reference sections, Point of Contact and Metadata Contact information was updated, and Process Steps were refined. Information about the data available for download and different Network Resource Name links and details were given in the Standard Order Process section. Minor typos were corrected. No data information was changed. The metadata available from a harvester may supersede metadata bundled within a download file. Users are advised to compare the metadata dates to determine which metadata file is most recent.