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://dx.doi.org/10.3133/ofr20151232

Suggested Citation: Dartnell, P., Kvitek, R.G., Ritchie, A.C., and Finlayson, D.P., 2015, Shaded-relief bathymetry, Offshore of Pigeon 

Point map area, California, sheet 2 in Cochrane, G.R., Watt, J.T., Dartnell, P., Greene, H.G., Erdey, M.D., Dieter, B.E., Golden, N.E., 

Johnson, S.Y., Endris, C.A., Hartwell, S.R., Kvitek, R.G., Davenport, C.W., Krigsman, L.M., Ritchie, A.C., Sliter, R.W., Finlayson, D.P., and 

Maier, K.L. (G.R. Cochrane and S.A. Cochran, eds.), California State Waters Map Series—Offshore of Pigeon Point, California: U.S. 

Geological Survey Open-File Report 2015–1232, pamphlet 40 p., 10 sheets, scale 1:24,000, http://dx.doi.org/10.3133/ofr20151232.

ISSN 2331-1258 (online) 

http://dx.doi.org/10.3133/ofr20151232

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

shading) and onshore topographic-lidar surveys (yellow shading). Also shown are data-collecting 

agencies (CSUMB, California State University, Monterey Bay, Seafloor Mapping Lab; FP, Fugro Pelagos; 

USGS, U.S. Geological Survey) and dates of surveys if known. Yellow line shows limit of California’s State 

Waters.

CSUMB,

 2007

 FP, 

 2006, 2007

USGS, 2009

Año Nuevo 

State Park

Pigeon Point

Limit of California’s 

 State Waters

122o25'

37o10'

122o0'

37o05'

20

DISCUSSION

This shaded-relief bathymetry map of the Offshore of Pigeon Point map area in central California was 

generated from bathymetry data collected by California State University, Monterey Bay (CSUMB), by Fugro 

Pelagos, and by the U.S. Geological Survey (USGS) (fig. 1). Mapping was completed between 2006 and 2009, 

using a combination of 400-kHz Reson 7125 and 244-kHz Reson 8101 multibeam echosounders, as well as a 

234-kHz SWATHplus bathymetric sidescan-sonar system. These mapping missions combined to collect 

bathymetry data from about the 10-m isobath to beyond the 3-nautical-mile limit of California’s State Waters.

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°; heave accuracy, ±5%, or 5 cm). To account for tidal-cycle fluctuations, Fugro 

Pelagos used StarFix HP and XP real-time kinematic (RTK) GPS receivers, and CSUMB used a NavCom 

2050 receiver; 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 RTK receivers.

During the USGS mapping mission, GPS data with real-time-kinematic corrections 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 (Ritchie and others, 2010).

Processed soundings from the different mapping missions were exported from the acquisition or processing software as XYZ files and bathymetric surfaces. All the surfaces were merged into one overall 2-mresolution bathymetric-surface model and clipped to the boundary of the map area. An illumination having an 

azimuth of 300° and from 45° above the horizon was then applied to the 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. In addition, lines at the borders of some surveys are the result of 

slight differences in depth, as measured by different mapping systems in different years. These various 

artifacts are made obvious by the hillshading process. 

Bathymetric contours were generated at 10-m intervals from the merged 2-m-resolution bathymetric 

surface. The merged surface was smoothed using the Focal Mean tool in ArcGIS and a circular neighborhood 

that has a radius of between 20 and 30 m (depending on the location). The contours were generated from this 

smoothed surface using the Spatial Analyst Contour tool in ArcGIS. The most continuous contour segments 

were preserved; smaller segments and isolated island polygons were excluded from the final output. 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 California Coastal Conservancy (available 

from National Oceanic and Atmospheric Administration [NOAA] Coastal Service Center’s Digital Coast 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/).

REFERENCE CITED

Ritchie, A.C., Finlayson, D.P., and Logan, J.B., 2010, Swath bathymetry surveys of the Monterey Bay area 

from Point Año Nuevo to Moss Landing, San Mateo, Santa Cruz, and Monterey Counties, California: 

U.S. Geological Survey Data Series 514, available at http://pubs.usgs.gov/ds/514/.

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

37°

36°40'

122°20' 122°

Santa Cruz

Monterey

Moss 

Landing

Pigeon

Point

Limit of California’s

State Waters

Area of

Map

CALIF.

MAP LOCATION

0 5 10 Kilometers

0 5 10Nautical Miles

121°40'

Monterey

Bay

1

U.S. Geological Survey; 

2

California State University, Monterey Bay, Seafloor Mapping Lab

Shaded-Relief Bathymetry, Offshore of Pigeon Point Map Area, California

By

Peter Dartnell,1 Rikk G. Kvitek,2 Andrew C. Ritchie,1 and David P. Finlayson1 

2015

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, 2015

MAGNETIC NORTH

13 / ° 1 2

TRUE NORTH

Shaded-relief bathymetry by Peter Dartnell, 2014. Data collected by Fugro Pelagos in 

2006–2007, by California State University, Monterey Bay, Seafloor Mapping Lab in 2007 

(data available at http://seafloor.otterlabs.org/index.html), and by U.S. Geological Survey 

in 2009 (data available at http://pubs.usgs.gov/ds/514/). Bathymetric contours by 

Mercedes D. Erdey, 2014

GIS database and digital cartography by Nadine E. Golden, 2013

Manuscript approved for publication December 4, 2015

Onshore elevation data from California Coastal Conservancy (available 

from National Oceanic and Atmospheric Administration [NOAA] Coastal 

Service Center’s Digital Coast 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

30

40

50

60

70

70

10

10

10

10

10

10

20

Año Nuevo 

 State Park

Pigeon Point

122°25' 122°20'

122°25' 122°20'

37°10'

37°05'

37°05'

37°10'

Open-File Report 2015–1232

Sheet 2 of 10

Pamphlet accompanies map

U.S. Department of the Interior

U.S. Geological Survey