Bathymetry Hillshade--Hueneme Canyon and Vicinity, California

The bathymetry and shaded-relief maps of the Hueneme Canyon and Vicinity map area in southern California were generated from data collected by California State University, Monterey Bay, Seafloor Mapping Lab (CSUMB), by the U.S. Geological Survey (USGS), and by Fugro Pelagos for the U.S. Army Corps of Engineers (USACE) Joint Lidar Bathymetry Technical Center of Expertise. All these mapping missions combined to collect bathymetry from the 0-m isobath to beyond the 3-nautical-mile limit of California's State Waters. During the CSUMB mapping missions, an Applanix position and motion compensation system (POS/MV) was used to accurately position the vessel 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, +/-.02 degrees; heave accuracy, +/-5 percent, or 5 cm). NavCom 2050 GPS receiver (CNAV) data were used to account for tidal-cycle fluctuations, and 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. Final 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). During the USGS mapping mission, GPS data and measurements of vessel motion (heave, pitch, and roll) were combined 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 the raw samples that discriminate the seafloor returns (soundings) from unintended targets in the water column. The original 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. Finally, the soundings were converted into a 2-m-resolution bathymetric-surface-model. During the Fugro Pelagos 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 first-return 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 2-m-resolution bathymetry data (CSMP survey blocks A - D) within this map were downloaded from http://seafloor.csumb.edu/SFMLwebDATA.htm

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

Merge all bathymetry data into 2-m-resolution bathymetry grid and clip to the Hueneme Canyon and vicinity, California, map boundary. To create the shaded-relief imagery, an illumination having an azimuth of 300 degrees and 45 degrees above the horizon was applied to the bathymetry grid.

Metadata was modified to bring up to current USGS PCMSC standards. Information for accompanying Scientific Investigations Report added to Abstract and Cross Reference sections. Point of Contact information was updated. USGS Thesaurus and keywords were added, and Process Steps were refined. Details about different Network Resource Name links was given in the Access Instructions section. Phone number for Metadata Contact was corrected. Minor typos were corrected. No data information was changed.