U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 7
PUBLICATION DATE: 08/07/1984
Station ID: 9416841 SUPERCEDED DATE: 04/21/2003
Name: ARENA COVE, PACIFIC OCEAN
CALIFORNIA
NOAA Chart: 18640 Latitude: 38° 54.8' N
USGS Quad: POINT ARENA Longitude: 123° 42.5' W
To reach the tidal bench marks from State Highway 1, take Iverson Road for 1.1
miles (1.8 km) to the waterfront. The tide staff and gage were located halfway
out the Arena Cove Pier. The bench marks are along the dirt and asphalt roads
east of the pier and along the beach south of the pier.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 6 1945
MONUMENTATION: Survey Disk VM#: 1005
AGENCY: PID#: JT9392
SETTING CLASSIFICATION: Bedrock
The bench mark is set in the top of a long narrow rock outcrop at the shoreline,
500 feet (152 m) south of Arena Cove pier, 250 feet (76 m) south of a small
stream emptying into the ocean, and 29 feet (9 m) west of the base of a high
cliff.
BENCH MARK STAMPING: 5 1945
MONUMENTATION: Survey Disk VM#: 1006
AGENCY: PID#: JT9391
SETTING CLASSIFICATION: Concrete Wall
The bench mark is set in the top of a retaining wall east of the boathouse at
the Arena Cove Coast Guard Lifeboat Station, just west of the curve in the
retaining wall, and 10 feet (3 m) from the east face of the boathouse.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 7
PUBLICATION DATE: 08/07/1984
Station ID: 9416841 SUPERCEDED DATE: 04/21/2003
Name: ARENA COVE, PACIFIC OCEAN
CALIFORNIA
NOAA Chart: 18640 Latitude: 38° 54.8' N
USGS Quad: POINT ARENA Longitude: 123° 42.5' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 6841 D 1977
MONUMENTATION: Survey Disk VM#: 1007
AGENCY: PID#: JT9390
SETTING CLASSIFICATION: Concrete Step
The bench mark is set in the second lowest step of the stairway leading to the
former Coast Guard quarters, 0.2 mile (0.3 km) east of the inshore end of the
Arena Cove pier, 100 feet (30.5 m) NNE of the centerline of Port Street, as it
leads to the pier, 52 feet (16 m) NNE from the northern corner of the smaller
and westernmost of two corrugated aluminum Shell Oil buildings, 6 feet (2 m)
west of the west corner of a double doored wooden former Coast Guard garage, and
0.4 foot (0.1 m) west of the eastern corner of the step.
BENCH MARK STAMPING: 6841 F 1978
MONUMENTATION: Survey Disk VM#: 1009
AGENCY: PID#: JT9393
SETTING CLASSIFICATION: Bedrock
The bench mark is set in the center of a 10 foot (3 m) by 15 foot (5 m) by 5
foot (2 m) high rock outcrop along the shoreline, 650 feet (198 m) south of the
Arena Cove pier, 154 feet (47 m) south of bench mark 6 1945, 30 feet (9 m) west
of the base of the cliff, and 19 feet (6 m) west of a 10 foot (3 m) high rock
pinnacle.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 7
PUBLICATION DATE: 08/07/1984
Station ID: 9416841 SUPERCEDED DATE: 04/21/2003
Name: ARENA COVE, PACIFIC OCEAN
CALIFORNIA
NOAA Chart: 18640 Latitude: 38° 54.8' N
USGS Quad: POINT ARENA Longitude: 123° 42.5' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 6841 G 1978
MONUMENTATION: Survey Disk VM#: 1010
AGENCY: PID:
SETTING CLASSIFICATION: Bedrock
The bench mark is set on the highest point of a 5 foot (2 m) by 10 foot (3 m) by
6 foot (2 m) high rock outcrop along the shoreline, 800 feet (244 m) south of
the Arena Cove pier, 161 feet (49 m) south of bench mark 6841 F 1978, and 23
feet (7 m) west of the base of the cliff.
BENCH MARK STAMPING: 6841 H 1979
MONUMENTATION: Survey Disk VM#: 1011
AGENCY: PID#: JT9388
SETTING CLASSIFICATION: Copper Clad Steel Rod
The bench mark is set along the north side of Port Road in the center of a nitch
at the bottom of a hill where a wood fence dips down and follows the road, 0.3
mile (0.5 km) east of the inshore end of the Arena Cove pier, 0.2 mile (0.3 km)
west of bench mark 6841 J 1979, 60 feet (18 m) SE of the most easterly of four
eucalyptus trees, 29 feet (9 m) north of the centerline of Port Road, 7.5 feet
(2.3 m) north of a gate in the wood fence, and 1.5 feet (0.5 m) north of a
4-inch by 4-inch by 4-foot high redwood witness post. The bench mark is 0.2
foot (0.1 m) below ground level, crimped to a copper clad steel rod driven 8
feet (2 m) to refusal, and encased in a 4-inch PVC pipe.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 7
PUBLICATION DATE: 08/07/1984
Station ID: 9416841 SUPERCEDED DATE: 04/21/2003
Name: ARENA COVE, PACIFIC OCEAN
CALIFORNIA
NOAA Chart: 18640 Latitude: 38° 54.8' N
USGS Quad: POINT ARENA Longitude: 123° 42.5' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 6841 J 1979
MONUMENTATION: Survey Disk VM#: 1012
AGENCY: PID#: JT9387
SETTING CLASSIFICATION: Copper Clad Steel Rod
The bench mark is set along the north side of Port Road, 0.5 mile (0.8 km) east
of the inshore end of the Arena Cove pier, 0.2 mile (0.3 km) east of bench mark
6841 H 1979, 56.5 feet (17.2 m) north of a utility pole located on the south
side of Port Road, 52.0 feet (15.8 m) west of the centerline of where a driveway
intersects Port Road, 33.0 feet (10.1 m) north of the centerline of Port Road,
and 2 feet (1 m) west of a 4-inch by 4-inch by 4-foot high redwood witness post.
The bench mark is 0.2 foot (0.1 m) below ground level, crimped to a copper clad
steel rod driven 4 feet (1 m) to refusal, and encased in a 4-inch PVC pipe.
BENCH MARK STAMPING: 6841 K 1980
MONUMENTATION: Survey Disk VM#: 1013
AGENCY: PID#: JT9389
SETTING CLASSIFICATION: Concrete Foundation
The bench mark is set in a 9.0 foot (2.7 m) by 2.5 foot (0.8 m) by 1.0 foot (0.3
m) deep concrete slab at the Chevron fuel tank farm, 79.0 feet (24.1 m) west of
a telephone pole tagged JP at the east end of the tank farm, 24 feet (7 m) north
of the centerline of Port Road, 3.5 feet (1.1 m) south of the south concrete
retaining wall surrounding the tank farm, and 0.7 foot (0.2 m) north of the
south edge of the concrete slab.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 7
PUBLICATION DATE: 08/07/1984
Station ID: 9416841 SUPERCEDED DATE: 04/21/2003
Name: ARENA COVE, PACIFIC OCEAN
CALIFORNIA
NOAA Chart: 18640 Latitude: 38° 54.8' N
USGS Quad: POINT ARENA Longitude: 123° 42.5' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 6841 M 1982
MONUMENTATION: Survey Disk VM#: 1014
AGENCY: PID:
SETTING CLASSIFICATION: Galvanized Steel Rod
The bench mark is set along the north side of Iverson Road, 461 feet (141 m)
west of bench mark 6841 H 1979, 22.9 feet (7.0 m) east of a road sign marked
Slow Children at Play, 19.5 feet (5.9 m) north of the centerline of Iverson
Road, 9.3 feet (2.8 m) south of the SW corner of a grove of trees, and 3.3 feet
(1.0 m) west of a metal witness post. The bench mark is 0.5 foot (0.2 m) below
ground level, crimped to a galvanized steel rod driven 10.0 feet (3.0 m) to
refusal, and encased in a 4-inch PVC pipe with a cap.
BENCH MARK STAMPING: 6841 L 1982
MONUMENTATION: Survey Disk VM#: 12487
AGENCY: PID:
SETTING CLASSIFICATION: Galvanized Steel Rod
The bench mark is set along the dirt road north of the Arena Cove Cafe, 210 feet
(64 m) east of bench mark 5 1945, 35 feet (11 m) SE of a telephone pole marked
32, 22.4 feet (6.8 m) NE of the NE corner of the blue and white Arena Cove Cafe,
15 feet (5 m) south of the centerline of the dirt road, and 3.6 feet (1.1 m)
east of a telephone pole with a No Parking sign and witness post sign attached.
The bench mark is 0.6 foot (0.2 m) below ground level, crimped to a galvanized
steel rod driven 33.5 feet (10.2 m) to refusal, and encased in a 4-inch PVC
pipe.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 6 of 7
PUBLICATION DATE: 08/07/1984
Station ID: 9416841 SUPERCEDED DATE: 04/21/2003
Name: ARENA COVE, PACIFIC OCEAN
CALIFORNIA
NOAA Chart: 18640 Latitude: 38° 54.8' N
USGS Quad: POINT ARENA Longitude: 123° 42.5' W
T I D A L D A T U M S
Tidal datums at ARENA COVE, PACIFIC OCEAN based on:
LENGTH OF SERIES: 3 YEARS
TIME PERIOD: 1979-1981
TIDAL EPOCH: 1960-1978
CONTROL TIDE STATION: 9414290 SAN FRANCISCO, CA
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in FEET:
HIGHEST OBSERVED WATER LEVEL (02/16/1980) = 8.67
MEAN HIGHER HIGH WATER MHHW = 5.86
MEAN HIGH WATER MHW = 5.20
MEAN TIDE LEVEL MTL = 3.18
MEAN LOW WATER MLW = 1.16
MEAN LOWER LOW WATER MLLW = 0.00
LOWEST OBSERVED WATER LEVEL (06/21/1978) = -2.02
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In FEET above:
Stamping or Designation MLLW MHW
6 1945 9.20 4.00
5 1945 20.54 15.34
6841 D 1977 24.54 19.34
6841 F 1978 9.88 4.68
6841 G 1978 12.89 7.69
6841 H 1979 25.41 20.21
6841 J 1979 45.87 40.67
6841 K 1980 18.44 13.24
6841 M 1982 20.81 15.61
6841 L 1982 18.36 13.16
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 7 of 7
PUBLICATION DATE: 08/07/1984
Station ID: 9416841 SUPERCEDED DATE: 04/21/2003
Name: ARENA COVE, PACIFIC OCEAN
CALIFORNIA
NOAA Chart: 18640 Latitude: 38° 54.8' N
USGS Quad: POINT ARENA Longitude: 123° 42.5' W
D E F I N I T I O N S
Mean Sea Level (MSL) is a tidal datum determined over a 19-year National Tidal
Datum Epoch. It pertains to local mean sea level and should not be confused
with the fixed datums of North American Vertical Datum of 1988 (NAVD88).
NAVD88 is a fixed datum derived from a simultaneous, least squares, minimum
constraint adjustment of Canadian/Mexican/United States leveling observations.
Local mean sea level observed at Father Point/Rimouski, Canada was held fixed as
the single initial constraint. NAVD88 replaces NGVD29 as the national
standard geodetic reference for heights. Bench mark elevations relative to
NAVD88 are available from NGS through the World Wide Web at
National Geodetic Survey.
NGVD29 is a fixed datum adopted as a national standard geodetic reference for
heights but is now considered superseded. NGVD29 is sometimes referred to as
Sea Level Datum of 1929 or as Mean Sea Level on some early issues of Geological
Survey Topographic Quads. NGVD29 was originally derived from a general
adjustment of the first-order leveling networks of the U.S. and Canada after
holding mean sea level observed at 26 long term tide stations as fixed.
Numerous local and wide-spread adjustments have been made since establishment in
1929. Bench mark elevations relative to NGVD29 are available from the National
Geodetic Survey (NGS) data base via the World Wide Web at
National Geodetic Survey.
NAVD88 and NGVD29 are fixed geodetic datums whose elevation relationships to
local MSL and other tidal datums may not be consistent from one location to
another.
The Vertical Mark Number (VM#) and PID# shown on the bench mark sheet are unique
identifiers for bench marks in the tidal and geodetic databases, respectively.
Each bench mark in either database has a single, unique VM# and/or PID# assigned.
Where both VM# and PID# are indicated, both tidal and geodetic elevations are
available for the bench mark listed.
The NAVD88 elevation is shown on the Elevations of Tidal Datums Table Referred
to MLLW only when two or more of the bench marks listed have NAVD88 elevations.
The NAVD88 elevation relationship shown in the table is derived from an average
of several bench mark elevations relative to tide station datum. As a result of
this averaging, NAVD88 bench mark elevations computed indirectly from the tidal
datums elevation table may differ slightly from NAVD88 elevations listed for
each bench mark in the NGS database.