Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply endorsement by the 

U.S. Government

This map was printed on an electronic plotter directly from digital files. Dimensional calibration may vary between electronic plotters 

and between X and Y directions on the same plotter, and paper may change size due to atmospheric conditions; therefore, scale and 

proportions may not be true on plots of this map.

For sale by U.S. Geological Survey, Information Services, Box 25286, Federal Center, Denver, CO 80225, 1–888–ASK–USGS

Digital files available at https://doi.org/10.3133/ofr20181023

Suggested Citation: Dartnell, P., and Kvitek, R.G., 2018, Shaded-relief bathymetry, Offshore of Gaviota map area, California, sheet 2 in

Johnson, S.Y., Dartnell, P., Cochrane, G.R., Hartwell, S.R., Golden, N.E., Kvitek, R.G., and Davenport, C.W. (S.Y. Johnson and S.A. 

Cochran, eds.), California State Waters Map Series—Offshore of Gaviota, California: U.S. Geological Survey Open-File Report 

2018–1023, pamphlet 41 p., 9 sheets, scale 1:24,000, https://doi.org/10.3133/ofr20181023.

ISSN 2331-1258 (online)

https://doi.org/10.3133/ofr20181023

Figure 1. Map showing areas of multibeam-echosounder and bathymetric-sidescan surveys (pink 

shading), bathymetric- and topographic-lidar surveys (orange diagonal lines), and publicly available 

onshore topographic-lidar data (yellow shading). Also shown are data-collecting agencies (FP, Fugro 

Pelagos; USACE, U.S. Army Corps of Engineers; USGS, U.S. Geological Survey) and dates of surveys if 

known.

USGS, 2007, 2008

USACE, 2009, 2010

FP, 2008

120°20' 120°15'

34°30'

34°25'

20

DISCUSSION

This shaded-relief bathymetry map of the Offshore of Gaviota map area in southern California was 

generated from acoustic-bathymetry data collected by the U.S. Geological Survey (USGS) and by Fugro 

Pelagos (fig. 1) in 2007 and 2008, using a combination of 400-kHz Reson 7125, 240-kHz Reson 8101, and 

100-kHz Reson 8111 multibeam echosounders, as well as a 234-kHz SEA SWATHplus bathymetric sidescansonar system. In addition, bathymetric- and topographic-lidar data was collected in the nearshore and coastal 

areas by the U.S. Army Corps of Engineers (USACE) Joint Lidar Bathymetry Technical Center of Expertise in 

2009 and 2010. These mapping missions combine to provide continuous bathymetry from the shoreline to the 

3-nautical-mile limit of California’s State Waters.

During the USGS mapping missions, GPS data with real-time-kinematic corrections were combined with 

measurements of vessel motion (heave, pitch, and roll) in a CodaOctopus F190 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. Further editing of the USGS 2007 bathymetric-sounding data 

was completed in 2016, and the final soundings were converted into a 2-m-resolution bathymetric-surfacemodel grid. 

During the Fugro Pelagos 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, with navigational input from GPS receivers. Smoothed Best 

Estimated Trajectory (SBET) files were postprocessed from logged POS-MV files. 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) and heave using the postprocessed SBET data 

(California State University, Monterey Bay, Seafloor Mapping Lab, 2016). 

Nearshore bathymetric-lidar data and acoustic-bathymetric data from within California’s State Waters 

were merged together as part of the 2013 National Oceanic and Atmospheric Administration (NOAA) Coastal 

California TopoBathy Merge Project (National Oceanic and Atmospheric Administration, 2013). Merged 

bathymetry data from within the Offshore of Gaviota map area were downloaded from this dataset and 

resampled to 2-m spatial resolution, then the reprocessed 2007 USGS bathymetry data were incorporated into 

the downloaded data. An illumination having an azimuth of 300° and from 45° above the horizon was then 

applied to the new bathymetric surface to create the shaded-relief imagery. Note that the ripple patterns and 

parallel lines that are apparent within the map area are data-collection and -processing artifacts. These various 

artifacts are made obvious by the hillshading process. 

Bathymetric contours were generated at 10-m intervals from a modified 2-m-resolution bathymetric 

surface. The most continuous contour segments were preserved; smaller segments and isolated island polygons 

were excluded from the final output. The contours were smoothed using a polynomial approximation with 

exponential kernel algorithm and a tolerance value of 60 m. The contours were then clipped to the boundary of 

the map area.

The onshore-area image was generated by applying the same illumination (azimuth of 300° and from 45° 

above the horizon) to 2-m-resolution topographic-lidar data from National Oceanic and Atmospheric Administration Office for Coastal Management’s Digital Coast (available at http://www.csc.noaa.gov/digitalcoast/

data/coastallidar/) and to 10-m-resolution topographic-lidar data from the U.S. Geological Survey’s National 

Elevation Dataset (available at http://ned.usgs.gov/).

REFERENCES CITED

California State University, Monterey Bay, Seafloor Mapping Lab, 2016, Southern California 2008 CSMP 

surveys: California State University, Monterey Bay, Seafloor Mapping Lab Data Library, accessed 

October 2016 at http://seafloor.otterlabs.org/SFMLwebDATA_SURVEYMAP.htm.

National Oceanic and Atmospheric Administration, 2013, 2013 NOAA Coastal California TopoBathy Merge 

Project: National Oceanic and Atmospheric Administration, National Centers for Environmental 

Information database, accessed October 2016 at http://www.ngdc.noaa.gov/docucomp/page?xml=NOAA/

NESDIS/NGDC/MGG/Lidar/iso/xml/2013_CA_TopoBathy_m2612.xml&view=getDataView&header=

none.

EXPLANATION

Amount of illumination

Illuminated (facing false sun)

In shadow (facing away from false sun)

Direction of illumination from false sun—Position of false sun is at 300° azimuth, 45° above 

horizon [arrow included in explanation for illustration purposes only; not shown on map]

Area of “no data”—Areas near shoreline not mapped owing to insufficient high-resolution 

seafloor mapping data; areas beyond 3-nautical-mile limit of California’s State Waters were 

not mapped as part of California Seafloor Mapping Program

3-nautical-mile limit of California’s State Waters

Bathymetric contour (in meters)—Derived from modified 2-m-resolution bathymetry grid. 

Contour interval: 10 m

120°30' 120° 119°30'

34°

34°30'

Limit of California’s

State Waters

Kilometers 0 5 10

Santa Barbara Channel

Area of

Map

Santa Barbara CALIF.

MAP LOCATION

Anacapa Is.

Santa Cruz Is.

Santa Rosa Is.

San Miguel Is.

1

U.S. Geological Survey;

2

California State University, Monterey Bay, Seafloor Mapping Lab

 Shaded-Relief Bathymetry, Offshore of Gaviota Map Area, California

By

Peter Dartnell1 and Rikk G. Kvitek2

2018

ONE MILE = 0.869 NAUTICAL MILES

BATHYMETRIC CONTOUR INTERVAL 10 METERS

1 .5 0 1 KILOMETER

1000 0 1000 2000 3000 4000 5000 6000 7000 FEET

1 1/2 0 1 MILE

SCALE 1:24 000

APPROXIMATE MEAN

DECLINATION, 2018

MAGNETIC NORTH

TRUE NORTH

12 / ° 1 2

Shaded-relief bathymetry by Peter Dartnell, 2016 (data collected by U.S. Geological 

Survey in 2007 and 2008, by Fugro Pelagos in 2008, and by U.S. Army Corps of Engineers 

Joint Lidar Bathymetry Technical Center of Expertise in 2009 and 2010). Bathymetric 

contours by Peter Dartnell, 2016

GIS database and digital cartography by Nadine E. Golden and Stephen R. Hartwell

Manuscript approved for publication February 12, 2018

Onshore elevation data from National Oceanic and 

Atmospheric Administration (NOAA) Office for Coastal 

Management's Digital Coast (available at 

http://www.csc.noaa.gov/digitalcoast/data/coastallidar/) and 

from U.S. Geological Survey’s National Elevation Dataset 

(available at http://ned.usgs.gov/). California's State Waters 

limit from NOAA Office of Coast Survey

Universal Transverse Mercator projection, Zone 10N

NOT INTENDED FOR NAVIGATIONAL USE

20

10

40

30

50

70

60

90

80

100

150

190

170

160

160

180

110

120

130

140

160

170

 Santa Ynez Mountains

 Gaviota

State Park

120°20' 120°15'

34°30'

34°25'

120°20' 120°15'

34°25'

34°30'

Open-File Report 2018–1023

Sheet 2 of 9

Pamphlet accompanies map

U.S. Department of the Interior

U.S. Geological Survey