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 http://pubs.usgs.gov/sim/3254/

Suggested Citation: Golden, N.E., Cochrane, G.R., and Krigsman, L.M., 2013, Ground-truth studies, Offshore of Ventura map area, 

California, sheet 6 in Johnson, S.Y., Dartnell, P., Cochrane, G.R., Golden, N.E., Phillips, E.L., Ritchie, A.C., Kvitek, R.G., Greene, H.G., 

Krigsman, L.M., Endris, C.A., Seitz, G.G., Gutierrez, C.I., Sliter, R.W., Erdey, M.D., Wong, F.L., Yoklavich, M.M., Draut, A.E., and Hart, P.E. 

(S.Y. Johnson and S.A. Cochran, eds.), California State Waters Map Series—Offshore of Ventura, California: U.S. Geological Survey 

Scientific Investigations Map 3254, pamphlet 42 p., 11 sheets, scale 1:24,000, available at http://pubs.usgs.gov/sim/3254/.

Figure 5. USGS-designed camera sled being launched off research vessel for ground-truth studies. Components onboard 

sled include four digital video camcorders, one 8-megapixel digital SLR camera, lasers for scale, and various strobe and 

video lights, as well as telemetry instrumentation that records depth, altitude, and compass heading.

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DISCUSSION

Between 2006 and 2010, the seafloor in the Offshore of Ventura map area in southern California was mapped by 

California State University, Monterey Bay (CSUMB), and the U.S. Geological Survey (USGS), using both multibeam 

echosounders and bathymetric sidescan-sonar units (see sheets 1, 2, 3). These mapping missions combined to collect 

bathymetry and acoustic-backscatter data from about the 10-m isobath to out beyond the 3-nautical-mile limit of 

California’s State Waters. In order to characterize the bathymetry and acoustic-backscatter data into geologically and 

biologically useful information, the USGS ground-truth-surveyed the data by towing camera sleds (fig. 5) over 

specific locations throughout the map area.

The ground-truth-surveys occurred on two separate cruises over a two-year period. The camera sleds were towed 

1 to 2 m over the seafloor, at speeds of between 1 and 2 nautical miles/hour. During the 2007 ground-truth cruise, a 

smaller USGS camera sled was used that housed two video cameras; one was forward looking, and the other was 

downward looking. The video was relayed in real time to the research vessel, where USGS and National Oceanic and 

Atmospheric Administration (NOAA) scientists recorded both the geologic and biologic character of the seafloor once 

every minute, using programmable keypads. During the 2008 ground-truth cruise, a larger camera sled was used that 

housed two video cameras (one forward looking, the other downward looking), a high-definition video camera, and an 

8-megapixel digital still camera, which captured a digital still photograph once every 30 seconds. The location and 

directions of the camera-sled tracklines were chosen in order to visually inspect areas thought to represent the full 

range of bottom hardness and rugosity in the map area.

In the context of marine-fisheries management, benthic-habitat complexity can be divided into abiotic (geologic) 

and biotic (biologic) components. Benthic-habitat complexity refers to the visual classification of local abiotic and 

biotic vertical relief and structure that may provide potential refuge for both juvenile and adult forms of various 

species. Only abiotic attributes (primary- and secondary-substrate composition) were used in the production of the 

seafloor-character map on sheet 5. Classifications of primary and secondary substrate are based on the Wentworth 

scale of sediment grain-size categories, except that the granule and pebble sizes have been grouped together into a 

class called “gravel,” and the clay and silt sizes have been grouped into a class called “mud.” Primary and secondary 

substrate constitute greater than 50 and 20 percent of the seafloor during an observation, respectively. 

This sheet contains a smaller, simplified (depth-zone symbology has been removed) version of the seafloorcharacter map (sheet 5), on which the camera-sled tracklines used to ground-truth the sonar data are indicated by 

aligned colored dots, each dot representing the location of a recorded observation. Primary- and secondary-substrate 

compositions are shown by differently colored dots. The map also shows the locations of the detailed views of 

seafloor character along some of the tracklines (Boxes A through D) that are highlighted on this sheet (figs. 1A 

through 4A, respectively). Also shown are locations of samples (triangles) from usSEABED (Reid and others, 2006) 

and by Barnard and others (2009) that were used to supplement the ground-truth surveys. The seafloor-character map 

shows that this area is mostly covered with sediment, except for two small outcroppings of rock in the nearshore 

region. 

Each detailed view (figs. 1A through 4A) shows the locations of camera-sled tracklines (aligned colored dots), as 

well as of the photographs (colored stars) taken along the tracklines. These photographs, which are representative of 

the seafloor, are displayed with a description of the observed seafloor characteristics recorded by USGS and NOAA 

scientists (figs. 1B through 1D, 2B through 2K, 3B through 3D, 4B through 4D). Only primary and secondary 

substrate are reported, although individual photographs may show more substrate types. Organisms, when present, are 

labeled on the photographs.

Ground-truth surveys in the Offshore of Ventura map area include approximately 6.81 trackline kilometers of 

video and 308 still photographs, in addition to 213 seafloor observations of abiotic and biotic attributes. A visual 

estimate of slope also was recorded.

GLOSSARY

Rugosity—A GIS-derived characterization of seafloor roughness, calculated as the ratio of the three-dimensional 

surface area of seafloor to the two-dimensional planar-base area, for each cell in the bathymetry grid.

Backscatter intensity—The amplitude of the reflected sonar signal (see sheet 3) used to infer the hardness of the 

bottom, determined after sonar-data processing has removed (as much as possible) the effects of water depth, angle of 

reflection, and bottom roughness.

Biocomplexity—The assessment of the presence or absence of biological structures that have the potential of 

providing shelter for fauna, determined by estimating the scale, the amount, and the morphology of biological relief 

(as described by Tissot and others, 2006).

Biocover—The visual estimate of the proportion of biologic cover by encrusting organisms: high, greater than 50 

percent; moderate, between 50 percent and 10 percent; low, less than 10 percent.

REFERENCES CITED

Barnard, P.L., Revell, D.L., Hoover, D., Warrick, J., Brocatus, J., Draut, A.E., Dartnell, P., Elias, E., Mustain, N., Hart, 

P.E., and Ryan, H.F., 2009, Coastal processes study of Santa Barbara and Ventura Counties, California: U.S. 

Geological Survey Open-File Report 2009–1029, 926 p., available at http://pubs.usgs.gov/of/2009/1029/.

Reid, J.A., Reid, J.M., Jenkins, C.J., Zimmerman, M., Williams, S.J., and Field, M.E., 2006, usSEABED—Pacific 

Coast (California, Oregon, Washington) offshore surficial-sediment data release: U.S. Geological Survey Data 

Series 182, available at http://pubs.usgs.gov/ds/2006/182/.

Tissot, B.N., Yoklavich, M.M., Love, M.S., York, K., and Amend, M., 2006, Benthic invertebrates that form habitat on 

deep banks off southern California, with special reference to deep sea coral: Fishery Bulletin, v. 104, p. 167–181.

EXPLANATION

Substrate class

Fine- to medium-grained smooth sediment—Low backscatter, low rugosity; typically mud to 

medium-grained sand; often rippled and (or) burrowed

Mixed smooth sediment and rock—Moderate to very high backscatter, low rugosity; typically 

coarse-grained sand, gravel, cobbles, and bedrock

Rock and boulder, rugose—High backscatter, high rugosity; typically boulders and rugose bedrock

Anthropogenic material—Related to development by humans

Location of real-time video observation and interpreted substrate class of seafloor

Fine- to medium-grained smooth sediment—Low backscatter, low rugosity; typically mud to 

medium-grained sand; often rippled and (or) burrowed

Mixed smooth sediment and rock—Moderate to very high backscatter, low rugosity; typically 

coarse-grained sand, gravel, cobbles, and bedrock

Rock and boulder, rugose—High backscatter, high rugosity; typically boulders and rugose bedrock

Location of digital still photograph and interpreted substrate class of seafloor

Fine- to medium-grained smooth sediment—Low backscatter, low rugosity; typically mud to 

medium-grained sand; often rippled and (or) burrowed

Mixed smooth sediment and rock—Moderate to very high backscatter, low rugosity; typically 

coarse-grained sand, gravel, cobbles, and bedrock

Rock and boulder, rugose—High backscatter, high rugosity; typically boulders and rugose bedrock

Interpreted substrate class depicted in digital still photograph—Indicated by colored frame around 

photograph (not shown on map; shown in figures only)

Fine- to medium-grained smooth sediment—Low backscatter, low rugosity; typically mud to 

medium-grained sand; often rippled and (or) burrowed

Mixed smooth sediment and rock—Moderate to very high backscatter, low rugosity; typically 

coarse-grained sand, gravel, cobbles, and bedrock

Rock and boulder, rugose—High backscatter, high rugosity; typically boulders and rugose bedrock

Sample localities

From usSEABED (Reid and others, 2006)

From Barnard and others (2009)

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

CALIF.

0 4 8

Nautical Miles

Kilometers 0 5 10

120° 119°40' 119°20' 119°

34°

34°20'

MAP LOCATION

Ventura

Santa Barbara

Anacapa

Island

Santa Cruz Island Santa Rosa Island

Area of

Map

Santa Barbara Channel

Limit of California’s

State Waters

1

U.S. Geological Survey;

2

National Oceanic and Atmospheric Administration, National Marine Fisheries Service

Ground-Truth Studies, Offshore of Ventura Map Area, California

By

Nadine E. Golden,1 Guy R. Cochrane,1 and Lisa M. Krigsman2

2013 

3 15 cm Cam70_Tape36 Image 4152 -21m

Figure 4B. Digital still photograph no. D3 (see fig. 4A for location). Relatively flat 

mud and sand deposit with degraded ripple pattern (water depth, 21 m). Abiotic 

complexity is low, biotic complexity is absent, and biocover is low. Biocover 

includes burrows (br). Distance between lasers (green dots) is 15 cm.

2 Cam70_Tape36 Image 4144 -21m 15 cm

Figure 4C. Digital still photograph no. D2 (see fig. 4A for location). Mud and sand 

deposit with degraded ripple pattern (water depth, 21 m). Abiotic complexity is 

low, biotic complexity is absent, and biocover is low. Biocover includes burrows 

(br), clam siphon (cs), and tube anemone (ta). Distance between lasers (green 

dots) is 15 cm.

cs

ta

br

15 cm 1Cam70_Tape35 Image 4106 -22m

Figure 4B. Digital still photograph no. D1 (see fig. 4A for location). Mud and sand 

deposit with degraded ripple pattern (water depth, 22 m). Abiotic complexity is 

low, biotic complexity is absent, and biocover is low. Biocover includes burrows 

(br). Distance between lasers (green dots) is 15 cm.

br

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D2 D1

Box D Figure 4A. Detailed view of seafloor character mapped southwest of Ventura, 

approximately 4.5 km offshore of Ventura River mouth (see Box D, on map, for location), 

showing locations of periodic real-time video observations (dots) and digital still 

photographs (stars; see figs. 4B through 4E) from camera line CAM70, cruise S-W1-09-SC.

Box A

br

15 cm 3 Cam43_Tape40_Image4760 -20m

Figure 3D. Digital still photograph no. C3 (see fig. 3A for location). Fine sand with 

sinuous-crested wave ripples (water depth, 20 m). Abiotic complexity is low, 

biotic complexity is absent, and biocover is low. Biocover includes crab (c). 

Distance between lasers (red dots) is 15 cm.

c

2 Cam43_Tape40 Image 4745 -21m 15 cm

Figure 3C. Digital still photograph no. C2 (see fig. 3A for location). Fine sand with 

symmetrical and sharp-crested wave ripples (water depth, 21 m). Abiotic 

complexity is low, biotic complexity is absent, and biocover is low. Distance 

between lasers (red dots) is 15 cm.

Cam43_Tape40 Image 4698 -21m 1 15 cm

Figure 3B. Digital still photograph no. C1 (see fig. 3A for location). Fine sand with 

symmetrical and sharp-crested wave ripples (water depth, 21 m). Abiotic 

complexity is low, biotic complexity is absent, and biocover is low. Distance 

between lasers (red dots) is 15 cm.

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C2 ^_ C1

Box C Figure 3A. Detailed view of seafloor character mapped southwest of Ventura, 

approximately 3 km offshore of Ventura River mouth (see Box C, on map, for location), 

showing locations of periodic real-time video observations (dots) and digital still 

photographs (stars; see figs. 3B through 3D) from camera line CAM43 cruise S-1C-08-SC.

Cam44_Tape41 

Image 4854-11m 10 15 cm

Figure 2K. Digital still photograph no. B10 (see fig. 2A for location). Sand with 

degraded ripples in confused, crossing pattern (water depth, 11 m). Abiotic 

complexity is low, biotic complexity is absent, and biocover is low. Biocover 

includes drift weed (dw). Distance between lasers (red dots are just out of view 

in this image but are visible in previous video frame) is 15 cm.

dw

9 Cam44_Tape41 Image 4847 -11m 15 cm

Figure 2J. Digital still photograph no. B9 (see fig. 2A for location). Boulders, 

cobbles, gravel, and scattered shells in area of rock outcrop (water depth, 11 

m). Abiotic complexity is low, biotic complexity is present, and biocover is 

moderate. Biocover includes scattered shells (ss), gorgonian (g), hydroid (h), 

and sponge (spo). Distance between lasers (red dots are just out of view in this 

image but are visible in previous video frame) is 15 cm.

spo g

h

ss

8 Cam44_Tape41 Image 4846 -11m 15 cm

Figure 2I. Digital still photograph no. B8 (see fig. 2A for location). Sand, gravel, 

and cobbles with scattered shells in area of rock outcrop (water depth, 11 m). 

Abiotic complexity is low, biotic complexity is absent, and biocover is moderate. 

Biocover includes scattered shells (ss) and sponge (spo). Distance between 

lasers (red dots are just out of view in this image but are visible in previous 

video frame) is 15 cm.

spo

ss

Cam44_Tape41 Image 4832 -10m 7 15 cm

Figure 2H. Digital still photograph no. B7 (see fig. 2A for location). Cobbles and 

gravel in area of rock outcrop (water depth, 10 m). Abiotic complexity is low, 

biotic complexity is present, and biocover is moderate. Biocover includes 

gorgonian (g) and sponge (spo). Distance between lasers (red dots are just out 

of view in this image but are visible in previous video frame) is 15 cm.

spo

g

Cam44_Tape41 Image 4821 -10m 6 15 cm

Figure 2G. Digital still photograph no. B6 (see fig. 2A for location). Gravel, 

cobbles, and boulders in area of rock outcrop (water depth, 10 m). Abiotic 

complexity is low, biotic complexity is present, and biocover is moderate. 

Biocover includes gorgonian (g) and sponge (spo). Distance between lasers 

(red dots are just out of view in this image but are visible in previous video 

frame) is 15 cm.

spo

g

Cam44_Tape41 Image 4816 -10m 5 15 cm

Figure 2F. Digital still photograph no. B5 (see fig. 2A for location). Cobbles and 

gravel with scattered shells in area of rock outcrop (water depth, 10 m). Abiotic 

complexity is low, biotic complexity is absent, and biocover is high. Biocover 

includes scattered shells (ss), sponge (spo), and hydroid (h). Distance between 

lasers (red dots are just out of view in this image but are visible in previous 

video frame) is 15 cm.

spo

h

ss

Cam44_Tape41 Image 4808 -10m 4 15 cm

Figure 2E. Digital still photograph no. B4 (see fig. 2A for location). Cobbles and 

gravel with deposits of sand in area of rock outcrop (water depth, 10 m). Abiotic 

complexity is moderate, biotic complexity is present, and biocover is high. 

Biocover includes gorgonian (g), sponge (spo), and bat star (bas). Distance 

between lasers (red dots are just out of view in this image but are visible in 

previous video frame) is 15 cm.

bas

spo

g

Cam44_Tape41 Image 4804 -10m 3 15 cm

Figure 2D. Digital still photograph no. B3 (see fig. 2A for location). Cobbles and 

gravel in area of rock outcrop (water depth, 10 m). Abiotic complexity is 

moderate, biotic complexity is present, and biocover is high. Biocover includes 

sponge (spo) and gorgonian (g). Distance between lasers (red dots) is 15 cm.

spo

g

15 cm 2 Cam44_Tape41 Image 4800 --10m

Figure 2C. Digital still photograph no. B2 (see fig. 2A for location). Rock patch 

(water depth, 10 m). Abiotic complexity is moderate, biotic complexity is 

present, and biocover is high. Biocover includes hydroid (h) and gorgonian (g). 

Distance between lasers (red dots) is 15 cm.

h

g

15 cm 1 Cam44_Tape41 Image 4785 -10m

Figure 2B. Digital still photograph no. B1 (see fig. 2A for location). Cobbles in 

area of rock outcrop (water depth, 10 m). Abiotic complexity is moderate, biotic 

complexity is present, and biocover is high. Biocover includes gorgonian (g), 

hydroid (h), and clam (cl). Distance between lasers (red dots) is 15 cm.

cl

g

h

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^_

B7

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B6

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B5

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B4

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Box B

Figure 2A. Detailed view of seafloor character mapped 0.5 km offshore, approximately 4 km 

northwest of Ventura River mouth (see Box B, on map, for location), showing locations of 

periodic real-time video observations (dots) and digital still photographs (stars; see figs. 2B 

through 2K) from camera line CAM44, cruise S-1C-08-SC.

3 15 cm Cam45_Tape42 Image4903 -13m

Figure 1D. Digital still photograph no. A3 (see fig. 1A for location). Fine sand with 

degraded sinuous wave ripples (water depth, 13 m). Abiotic complexity is low, 

biotic complexity is absent, and biocover is low. Distance between lasers (red 

dots are just out of view in this image but are visible in previous video frame) is 

15 cm.

2 Cam45_Tape42 Image4890 -14m 15 cm

ss

Figure 1C. Digital still photograph no. A2 (see fig. 1A for location). Fine to coarse 

sand with degraded wave ripples (water depth, 14 m). Abiotic complexity is low, 

biotic complexity is absent, and biocover is low. Biocover includes scattered 

shells (ss). Distance between lasers (red dots are just out of view in this image 

but are visible in previous video frame) is 15 cm.

1Cam45_Tape42 Image4876 -15m 15 cm

Figure 1B. Digital still photograph no. A1 (see fig. 1A for location). Fine to coarse 

sand with degraded wave ripples (water depth, 15 m). Abiotic complexity is low, 

biotic complexity is absent, and biocover is low. Biocover includes scattered 

shells (ss). Distance between lasers (red dots are just out of view in this image 

but are visible in previous video frame) is 15 cm.

ss

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A2

A1

Box A

Figure 1A. Detailed view of seafloor character mapped 1.5 km offshore of Pitas Point, 

approximately 8 km northwest of Ventura River mouth (see Box A, on map, for location), 

showing locations of periodic real-time video observations (dots) and digital still photographs 

(stars; see figs. 1B through 1D), from camera line CAM45, cruise S-1C-08-SC.

ONE MILE = 0.869 NAUTICAL MILES

1 0.5 0 1 KILOMETER

7000 3500 0 7000 FEET

2 1 0 2 MILES

SCALE 1:50 000

APPROXIMATE MEAN

DECLINATION, 2013

MAGNETIC NORTH

12 / ° 1 2

TRUE NORTH

Seafloor-character map simplified from map on sheet 

5, this report. Video observations recorded and digital 

still photographs taken in 2007-2008. Sample localities 

from usSEABED (Reid and others, 2006) and from 

Barnard and others (2009)

GIS database and digital cartography by Nadine E. 

Golden and Eleyne L. Phillips

Edited by Taryn A. Lindquist

Manuscript approved for publication March 11, 2013 

Onshore elevation data from NOAA Coastal Services Center 

(data collected by EarthData International in 2002-2003). 

Offshore shaded-relief bathymetry from map on sheet 2, this 

report. California's State Waters limit from NOAA Office of 

Coast Survey

Universal Transverse Mercator projection, Zone 11N

NOT INTENDED FOR NAVIGATIONAL USE

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119°20'

119°20'

119°25'

119°25'

119°15'

34°20'

34°20'

34°15'

34°15'

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Ventura

Santa Clara

 River

D Ventura Harbor

C

B

A

Scientific Investigations Map 3254

Sheet 6 of 11

Pamphlet accompanies map

U.S. Department of the Interior

U.S. Geological Survey