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/3306/

Suggested Citation: Golden, N.E., Cochrane, G.R., Erdey, M.D., and Krigsman, L.M., 2014, Ground-truth studies, Offshore of San 

Gregorio map area, California, sheet 6 in Cochrane, G.R., Dartnell, P., Greene, H.G., Watt, J.T., Golden, N.E., Endris, C.A., Phillips, E.L., 

Hartwell, S.R., Johnson, S.Y., Kvitek, R.G., Erdey, M.D., Bretz, C.K., Manson, M.W., Sliter, R.W., Ross, S.L., Dieter, B.E., and Chin, J.L. 

(G.R. Cochrane and S.A. Cochran, eds.), California State Waters Map Series—Offshore of San Gregorio, California: U.S. Geological 

Survey Scientific Investigations Map 3306, pamphlet 38 p., 10 sheets, scale 1:24,000, http://dx.doi.org/10.3133/sim3306.

ISSN 2329-132X (online)

http://dx.doi.org/10.3133/sim3306

Figure 7. USGS-designed camera sled being 

loaded onto research vessel in preparation 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.

#

^

^

^

!

!

!

DISCUSSION

Between 2006 and 2007, the seafloor in the Offshore of San Gregorio map area in northern California was mapped by Fugro 

Pelagos and by California State University, Monterey Bay (CSUMB), using multibeam echosounders (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 a camera sled (fig. 7) over specific locations 

throughout the map area in 2007.

During the ground-truth-survey cruise, the camera sled was towed 1 to 2 m over the seafloor, at speeds of between 1 and 2 nautical 

miles/hour. The sled housed two standard-definition (640×480 pixel resolution) video cameras (one forward looking, the other downward looking), a high-definition (1,080×1,920 pixel resolution) video camera, and an 8-megapixel digital still camera, which captured a 

digital still photograph once every 30 seconds. 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. 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 (1922) scale of sediment grain-size categories, and the sand, cobble, and boulder sizes 

are classified as in Wentworth (1922). However, the difficulty in distinguishing the finest divisions in the Wentworth (1922) scale during 

video observations made it necessary to aggregate some grain-size classes: 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.” In addition, hard bottom and clasts larger 

than boulder size are classified as “rock.” Primary and secondary substrate, by definition, 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 seafloor-character map (sheet 5), 

on which the camera-sled tracklines used to ground-truth-survey 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 F) that are 

highlighted on this sheet (figs. 1A, 2A, 3A, 4A, 5A, 6A). Also shown are locations of samples (triangles) from usSEABED (Reid and 

others, 2006) that were used to supplement the ground-truth surveys. The seafloor-character map shows that this area is predominately 

covered by sandy sediment (see, for example, figs. 1B, 1E, 1F), but it also includes several areas of rocky outcrops. The sandy sediment 

is characterized by sharp-crested, oscillatory ripples (typical wavelengths, 5 to 15 cm), and the sandy-shelf areas are typified by low 

abiotic complexity, low biotic complexity, and low biocover. Several large, isolated areas of sedimentary-rock outcrop are present in all 

water depths (see, for example, figs. 2E, 3F, 3G, 3I, 4D, 5C, 6C). High-relief rock outcrops support high biocover, including groundfish 

(see, for example, figs. 1D, 2E, 3C, 4D, 5E, 6B). Small areas of moderately to poorly sorted, coarse-grained sand and gravel are located 

along rock outcrops (see, for example, fig. 1C).

Each detailed view (figs. 1A, 2A, 3A, 4A, 5A, 6A) 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 1F; 2B through 2E; 

3B through 3K; 4B through 4F; 5B through 5E; 6B, 6C). Only primary and secondary substrates 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 San Gregorio map area include approximately 10.5 trackline kilometers of video and 675 

still photographs, in addition to 611 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

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.

Wentworth, C.K., 1922, A scale of grade and class terms for clastic sediments: Journal of Geology, v. 30, p. 377–392.

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)

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

Kilometers 0 5 10

0 5 10Nautical Miles

122°40' 122°20'

38°

37°40'

37°20'

San

Francisco

Bay

San

Francisco

Area of

Map

Limit of California’s

State Waters

CALIF.

MAP LOCATION

1

U.S. Geological Survey;

2

National Oceanic and Atmospheric Administration, National Marine Fisheries Service 

Ground-Truth Studies, Offshore of San Gregorio Map Area, California

By

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

2014

15 cm 2 Cam10_Tape13 Image 1699 -30m 

Figure 6C. Digital still photograph no. F2 (see fig. 

6A for location). Rugose rock outcrop (water 

depth, 30 m). Abiotic complexity is high, biotic 

complexity is absent, and biocover is high. 

Biocover includes encrusting sponges (spo), 

hydroids (h), strawberry anemones (sta), and cup 

corals (cc). Distance between lasers (red dots 

are just out of view in this image but are visible in 

previous video frame) is 15 cm.

h spo

sta

cc

15 cm 1 Cam10_Tape13 Image 1524 -24m 

Figure 6B. Digital still photograph no. F1 (see fig. 6A 

for location). Rugose rock outcrop with boulders 

(water depth, 24 m). Abiotic complexity is high, biotic 

complexity is absent, and biocover is moderate. 

Biocover includes bat star (bas), 3-dimensional 

sponge (spo3D), ronquil (r), and cup corals (cc). 

Distance between lasers (red dots) is 15 cm. 

r

spo3D

bas

cc

^_

^_

Box F

F2

F1

Figure 6A. Detailed view of seafloor character 

mapped southwest of Pescadero State Beach, 

approximately 2 km offshore (see Box F, on 

map, for location), showing locations of 

periodic real-time video observations (dots) 

and digital still photographs (stars; see figs. 6B, 

6C) from camera line CAM10, cruise 

F–3–07–NC.

15 cm 4 Cam10_Tape13 Image 1625 -18m

Figure 5E. Digital still photograph no. E4 (see fig. 5A for location). Interface 

between rugose rock outcrop and sand with shells (water depth, 18 m). 

Abiotic complexity is high, biotic complexity is absent, and biocover is high. 

Biocover includes bat star (bas) and encrusting sponges (spo). Distance 

between lasers (only one red dot is visible in this image, but both are visible 

in previous video frame) is 15 cm.

spo bas

Cam10_Tape13 Image 1571 -20m 15 cm 3

Figure 5D. Digital still photograph no. E3 (see fig. 5A for location). Mixed 

boulders, cobbles, and shell hash overlying rock (water depth, 20 m). 

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

is low. Biocover includes sea anemone (sa). Distance between lasers 

(only one red dot is visible in this image, but both are visible in previous 

video frame) is 15 cm.

sa

Cam10_Tape13 Image 1527 -16m 15 cm 2

Figure 5C. Digital still photograph no. E2 (see fig. 5A for location). Rugose 

rock outcrop (water depth, 16 m). Abiotic complexity is high, biotic 

complexity is absent, and biocover is high. Biocover includes bat star 

(bas), red algae (ra), and strawberry anemones (sta). Distance between 

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

previous video frame) is 15 cm.

ra bas

sta

15 cm 1 Cam10_Tape13 Image 1476 -23m 

Figure 5B. Digital still photograph no. E1 (see fig. 5A for location). Fine 

sand with sharp-crested, oscillatory ripples (water depth, 23 m). Abiotic 

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

Distance between lasers (red dots) is 15 cm.

^_

^_

_^

_^

Box E

E4

E3

E2

E1

Figure 5A. Detailed view of seafloor character mapped northwest of Pescadero State Beach, 

approximately 1.5 km offshore (see Box E, on map, for location), showing locations of periodic 

real-time video observations (dots) and digital still photographs (stars; see figs. 5B through 5E) 

from camera line CAM10, cruise F–3–07–NC.

15 cm 5 Cam11_Tape15 Image 1726 -40m

Figure 4F. Digital still photograph no. D5 

(see fig. 4A for location). 

Unconsolidated, fine- to 

medium-grained sand and shell hash 

with sharp-crested interference ripples 

(water depth, 40 m). Abiotic complexity 

is low, biotic complexity is absent, and 

biocover is low. Biocover includes 

brittle star arms (bs). Distance between 

lasers (red dots) is 15 cm. bs

Cam11_Tape14 Image 1687 -40m 15 cm 4

Figure 4E. Digital still photograph no. D4 

(see fig. 4A for location). Angular 

boulders and cobbles (water depth, 40 

m). Abiotic complexity is moderate, 

biotic complexity is absent, and 

biocover is moderate. Biocover includes 

bat stars (bas), frilly sea cucumber (fsc), 

cup corals (cc), and 3-dimensional 

sponge (spo3D). Distance between 

lasers (red dots are just out of view in 

this image but are visible in previous 

video frame) is 15 cm. 

bas

spo3D

fsc

cc

3 Cam11_Tape14 Image 1567 -41m 15 cm

Figure 4D. Digital still photograph no. D3 (see fig. 4A for location). 

Rugose rock outcrop that has thin cover of soft, unconsolidated 

sediment (water depth, 41 m). Abiotic complexity is high, biotic 

complexity is absent, and biocover is moderate. Biocover includes 

encrusting sponges (spo), 3-dimensional sponges (spo3D), cup corals 

(cc), 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. 

spo3D bas

spo

cc

Cam11_Tape14 Image 1549 -41m 2 15 cm

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

Boulders mixed with sand and shells (water depth, 41 m). Abiotic 

complexity is moderate, biotic complexity is absent, and biocover is 

moderate. Biocover includes kelp greenling (kg), cup corals (cc), 

encrusting sponges (spo), 3-dimensional sponges (spo3D), and bat 

stars (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

spo3D kg spo

cc

15 cm 1 Cam11_Tape14 Image 1473 -40m 

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

Unconsolidated, fine- to medium-grained sand with sharp-crested 

interference ripples (water depth, 40 m). Abiotic complexity is low, biotic 

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

pens (sp). Distance between lasers (red dots are just out of view in this 

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

sp

^_

^_

^_

_^

^_

Box D

D5

D4

D3

D2

D1

Figure 4A. Detailed view of seafloor character mapped southwest of San Gregorio State 

Beach, approximately 5 km offshore (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 4F) from camera line CAM11, cruise F–3–07–NC. 

Cam12_Tape16 Image 1644 -30m 15 cm 10

Figure 3K. Digital still 

photograph no. C10 

(see fig. 3A for location).

Unconsolidated, fine- to 

medium-grained sand 

with sharp-crested 

ripples in confused 

pattern (water depth, 30 

m). Abiotic complexity 

is low, biotic complexity 

is absent, and biocover 

is moderate. Biocover 

includes tubeworms 

(tw). Distance between 

lasers (only one red dot 

is visible in this image, 

but both are visible in 

previous video frame) is 

15 cm.

tw

15 cm 9 Cam12_Tape16 Image 1623 -30m 

Figure 3J. Digital still 

photograph no. C9 (see 

fig. 3A for location). 

Boulders, cobbles, and 

gravel (water depth, 30 

m). Abiotic complexity 

is moderate, biotic 

complexity is absent, 

and biocover is moderate. Biocover includes 

bat star (bas) and cup 

corals (cc). Distance 

between lasers (red 

dots are just out of view 

in this image but are 

visible in previous video 

frame) is 15 cm. 

bas

cc

Cam12_Tape16 Image 1615 -29m 15 cm 8

Figure 3I. Digital still 

photograph no. C8 (see 

fig. 3A for location). 

Rounded to subrounded 

boulders overlying rock 

(water depth, 29 m). 

Abiotic complexity is 

high, biotic complexity 

is absent, and biocover 

is moderate. Biocover 

includes rainbow star 

(rs), cup corals (cc), and 

tubeworms (tw). Distance between lasers 

(red dots are just out of 

view in this image but 

are visible in previous 

video frame) is 15 cm.

rs

cc

tw

7 Cam12_Tape16 Image 1585 -35m 15 cm

Figure 3H. Digital still 

photograph no. C7 (see 

fig. 3A for location). 

Mixed boulders, cobbles, 

and shell hash overlying 

rock (water depth, 35 m). 

Abiotic complexity is 

moderate, biotic complexity is absent, and 

biocover is low. Biocover 

includes encrusting 

sponge (spo) and cup 

corals (cc). Distance 

between lasers (only one 

red dot is visible in this 

image, but both are 

visible in previous video 

frame) is 15 cm.

cc

spo

6 Cam12_Tape16 Image 1568 -29m 15 cm

Figure 3G. Digital still photograph no. C6 (see fig. 3A for location). Rounded to 

subrounded boulders overlying rock (water depth, 29 m). Abiotic complexity is 

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

encrusting sponges (spo), encrusting coralline algae (ca), and cup corals (cc). 

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

visible in previous video frame) is 15 cm.

cc

spo

ca

15 cm 5 Cam12_Tape16 Image 1554 -33m 

Figure 3F. Digital still photograph no. C5 (see fig. 3A for location). Boulders, 

cobbles, and sand with shell hash (water depth, 33 m). Abiotic complexity is moderate, biotic complexity is absent, and biocover is moderate. Biocover includes 

frilly sea cucumber (fsc); cup corals (cc); blackeye goby, Rhinogobiops nicholsii

(beg); 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

cc fsc

beg

Cam12_Tape16 Image 1526 -35m 4 15 cm

Figure 3E. Digital still photograph no. C4 (see fig. 3A for location). Mixed 

boulders and cobbles overlying rock (water depth, 35 m). Abiotic complexity is moderate, biotic complexity is absent, and biocover is low. Biocover 

includes short-spined sea star (ssst) and cup corals (cc). Distance 

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

in previous video frame) is 15 cm.

ssst

cc

15 cm 3 Cam12_Tape16 Image 1497 -33m 

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

rock outcrop and boulders (water depth, 33 m). Abiotic complexity is high, 

biotic complexity is absent, and biocover is high. Biocover includes cup 

corals (cc), encrusting sponges (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

cc

Cam12_Tape16 Image 1480 -35m 

15 cm 2

Figure 3C. Digital still photograph no. C2 (see fig. 3A for location). Low-relief 

rock that has thin cover of sand and shell hash (water depth, 35 m). Abiotic 

complexity is moderate, biotic complexity is absent, and biocover is 

moderate. Biocover includes rockfish (rf), cup corals (cc), gray puffball 

sponge (gps), 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

rf

cc

gps

15 cm 1 Cam12_Tape16 Image 1461 -36m 

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

between rugose rock outcrop and sand with gravel and boulders (water 

depth, 36 m). Abiotic complexity is high, biotic complexity is absent, and 

biocover is moderate. Biocover includes cup corals (cc), encrusting 

sponges (spo), and bat stars (bas). Distance between lasers (red dots are 

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

spo

bas

cc

Figure 3A. Detailed view of seafloor character mapped southwest of San Gregorio State 

Beach, approximately 4 km offshore (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 3K) from camera line CAM12, cruise F–3–07–NC.

Box C

C8 C9 C10 C7

C6

C5

C4 C1 C2 C3 ^_ ^_ ^_ _^

^_

_^

^_

^_ ^_ ^_

Cam13_Tape17 Image 1508 -26m 

15 cm

4

Figure 2E. Digital still photograph 

no. B4 (see fig. 1A for location). 

Mixed boulders and cobbles 

overlying bedrock (water depth, 26 

m). Abiotic complexity is moderate, 

biotic complexity is absent, and 

biocover is moderate. Biocover 

includes short-spined sea star 

(ssst) and encrusting sponges 

(spo). Distance between lasers 

(red dots are just out of view in this 

image but are visible in previous 

video frame) is 15 cm. 

ssst

spo

15 cm 3 Cam13_Tape17 Image 1502 -26m 

Figure 2D. Digital still photograph 

no. B3 (see fig. 1A for location). 

Mixed gravel and fine sand with 

shells (water depth, 26 m). Abiotic 

complexity is moderate, biotic 

complexity is absent, and biocover 

is moderate. Biocover includes 

encrusting 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.

spo

bas

Cam13_Tape17 Image 1485 -27m 

15 cm 2

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

between sand with shell hash and mixed boulders and cobbles (water 

depth, 27 m). Abiotic complexity is moderate, biotic complexity is absent 

and biocover is moderate. Biocover includes sea anemone (sa) and 

encrusting 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

sa

15 cm 1Cam13_Tape17 Image 1448 -27m

Figure 2B. Digital still photograph no. B1 (see fig. 2A for location). Fineto medium-grained sand with sharp-crested ripples in confused pattern 

(water depth, 27 m). Abiotic complexity is low, biotic complexity is 

absent, and biocover is moderate. Biocover includes tubeworm (tw), 

hydroid (h), and bat star (bas). Distance between lasers (red dots) is 15 

cm.

h

bas

tw

^_

^_

^_ ^_

B4

B3

B2

B1

Box B

Figure 2A. Detailed view of seafloor character mapped southwest of San Gregorio State 

Beach, approximately 3 km offshore (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 2E) from camera line CAM13, cruise F–3–07–NC.

Cam1_Tape1 Image 1421 -27m 

15 cm

5

Figure 1F. Digital still photograph 

no. A5 (see fig. 1A for location). 

Unconsolidated, fine- to 

medium-grained sand with 

sharp-crested ripples in confused 

pattern (water depth, 27 m). Abiotic 

complexity is low, biotic 

complexity is absent, and biocover 

is low. Biocover includes 

tubeworm (tw) and drift weed (dw). 

Distance between lasers (red dots) 

is 15 cm. 

tw

dw

15 cm 4 Cam1_Tape1 Image 1397 -29m 

Figure 1E. Digital still photograph no. 

A4 (see fig. 1A for location). 

Unconsolidated, fine- to 

medium-grained sand with 

sharp-crested ripples in confused 

pattern (water depth, 29 m). Abiotic 

complexity is low, biotic complexity is 

absent, and biocover is low. Distance 

between lasers (green dots) is 15 cm. 

15 cm 3 Cam1_Tape1 Image 1384 -30m 

cc

tw

bas sa

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

Rounded to subrounded boulders and rugose rock (water depth, 30 m). 

Abiotic complexity is high, biotic complexity is absent, and biocover is 

high. Biocover includes bat star (bas); sea anemone (sa); cup corals (cc); 

frilly sea cucumbers (fsc); blackeye goby, Rhinogobiops nicholsii (beg); 

and ronquil (r). Distance between lasers (red dots are just out of view in 

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

fsc

beg

r

15 cm 2 Cam1_Tape1 Image 1377 -29m 

tw

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

Mixed gravel and cobbles with fine sand (water depth, 29 m). Abiotic 

complexity is moderate, biotic complexity is absent, and biocover is 

moderate. Biocover includes clam siphon (cs) and tubeworms (tw). 

Distance between lasers (red dots) is 15 cm.

cs

15 cm 1 Cam1_Tape1 Image 1330 -31m 

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

Unconsolidated, fine- to medium-grained sand with sharp-crested 

ripples in confused pattern (water depth, 31 m). Abiotic complexity is 

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

lasers (red dots) is 15 cm. 

^_

^_

^_

^_

Box A ^_A5

A4

A3

A2

A1

Figure 1A. Detailed view of seafloor character mapped northwest of San Gregorio State Beach, 

approximately 4.5 km offshore (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 1F) 

from camera line CAM1, cruise F–3–07–NC.

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, 2014

MAGNETIC NORTH

13 / ° 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. Sample localities from 

usSEABED (Reid and others, 2006)

GIS database and digital cartography by Nadine E. 

Golden and Eleyne L. Phillips

Edited by Taryn A. Lindquist

Manuscript approved for publication June 30, 2014

Onshore elevation data collected by Photoscience in 2005 for 

U.S. Geological Survey and County of San Mateo. 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 10N

NOT INTENDED FOR NAVIGATIONAL USE

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^__^ ^__^ ^_

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_^^_

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_^

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122°30' 122°25'

122°30' 122°25'

37°20'

37°15'

37°20'

37°15'

A

B

C

D

E

F

San Gregorio

 State Beach

 Pescadero

 State Beach

_^

Scientific Investigations Map 3306

Sheet 6 of 10

Pamphlet accompanies map

U.S. Department of the Interior

U.S. Geological Survey