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Datums Page Page 1 of 7
Station ID: 9416409 PUBLICATION DATE: 07/08/2013
Name: GREEN COVE, PACIFIC OCEAN
CA
NOAA Chart: 18640 Latitude: 38° 42.3' N ( 38.70433)
USGS Quad: STEWARTS POINT Longitude: 123° 27.0' W (-123.44939)
To reach the tidal bench marks from the Post Office in Gualala, proceed SE on
Highway 1 for 10.1 km (6.3 mi) to Headlands Reach, turn right on Headlands Reach
and proceed 0.3 km (0.2 mi) SW to the end of Headlands Reach at the intersection
with Green Cove Drive. Park and continue on foot 150 m (490 ft) SW on a dirt
trail to a rock headland. The tide gauges were located on the bare rock outcrop
below the edge of vegetation and the orifices were located on a rock wall on the
south side of the rock headland. The bench marks are located within 0.5 km (0.3
mi) along the rock shoreline.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 6409 B 2012
DESIGNATION: 941 6409 B
MONUMENTATION: Tidal Station disk VM#: 20630
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Bedrock OPUS PID#: BBCX03
LATITUDE: 38° 42.3' N ( 38.70439) LONGITUDE: 123° 27.0' W (-123.44956)
The primary bench mark is a disk set in bedrock, 38.53 m (126.4 ft)
east-southeast of bench mark 941 6409 A, 31.90 m (104.7 ft) south of the end of
the dirt trail at the edge of vegetation and 8.07 m (26.5 ft) SW of the highest
rock point on this headland.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 7
Station ID: 9416409 PUBLICATION DATE: 07/08/2013
Name: GREEN COVE, PACIFIC OCEAN
CA
NOAA Chart: 18640 Latitude: 38° 42.3' N ( 38.70433)
USGS Quad: STEWARTS POINT Longitude: 123° 27.0' W (-123.44939)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 6409 A 2012
DESIGNATION: 941 6409 A
MONUMENTATION: Tidal Station disk VM#: 20629
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Bedrock OPUS PID:
LATITUDE: 38° 42.3' N ( 38.70453) LONGITUDE: 123° 27.0' W (-123.45000)
The bench mark is a disk set in bedrock, 38.53 m (126.4 ft) WNW of bench mark
941 6409 B, 37.15 m (121.9 ft) WSW of the end of the dirt trail at the edge of
vegetation and 3.75 m (12.3 ft) north of the nearest prominent rock high point.
BENCH MARK STAMPING: 6409 C 2012
DESIGNATION: 941 6409 C
MONUMENTATION: Tidal Station disk VM#: 20631
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Bedrock OPUS PID:
LATITUDE: 38° 42.2' N ( 38.70378) LONGITUDE: 123° 26.9' W (-123.44872)
The bench mark is a disk set in bedrock, 22.05 m (72.3 ft) SW of a multi-use
dirt trail along the shoreline, 16.22 m (53.2 ft) NW of the nearest prominent
rock high point that is also attached to the higher sand bluff with vegetation,
15.05 m (49.4 ft) NE of a narrow slot canyon that extends down to the ocean and
0.75 m (2.5 ft) higher than the surrounding rock.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 7
Station ID: 9416409 PUBLICATION DATE: 07/08/2013
Name: GREEN COVE, PACIFIC OCEAN
CA
NOAA Chart: 18640 Latitude: 38° 42.3' N ( 38.70433)
USGS Quad: STEWARTS POINT Longitude: 123° 27.0' W (-123.44939)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 6409 D 2012
DESIGNATION: 941 6409 D
MONUMENTATION: Tidal Station disk VM#: 20632
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Bedrock OPUS PID:
LATITUDE: 38° 42.2' N ( 38.70311) LONGITUDE: 123° 26.9' W (-123.44786)
The bench mark is a disk set in bedrock, 41.72 m (136.9 ft) SE of the trail
along the shoreline where the smaller trail to the rock headland departs, 14.57
m (47.8 ft) SW of the highest rock point on the headland and 2.36 m (7.7 ft) NE
of a slight projection of rock which is over the top of a cave at sea level.
BENCH MARK STAMPING: 6409 E 2012
DESIGNATION: 941 6409 E
MONUMENTATION: Tidal Station disk VM#: 20633
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Rock outcrop OPUS PID:
LATITUDE: 38° 42.2' N ( 38.70364) LONGITUDE: 123° 26.8' W (-123.44625)
The bench mark is a disk set in a rock outcrop underneath a large evergreen
tree, 19.87 m (65.2 ft) west of the west end of a wooden fence, 8.97 m (29.4 ft)
SSE of an 8 inch by 8 inch wooden post for trail marker 13, 7.29 m (23.9 ft) SSW
of the centerline of the trail along the bluff, 6.12 m (20.1 ft) SE of a wooden
fence and 3.65 m (12.0 ft) NW of the closest side of a tree trunk at the edge of
the cliff over the water.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 7
Station ID: 9416409 PUBLICATION DATE: 07/08/2013
Name: GREEN COVE, PACIFIC OCEAN
CA
NOAA Chart: 18640 Latitude: 38° 42.3' N ( 38.70433)
USGS Quad: STEWARTS POINT Longitude: 123° 27.0' W (-123.44939)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: STENGLE 2 NO 2 1929
DESIGNATION: STENGLE 2 RM 2
MONUMENTATION: Reference Mark disk VM#: 20634
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#: JT2779
SETTING CLASSIFICATION: Rock outcrop OPUS PID:
LATITUDE: 38° 42.1' N ( 38.70086) LONGITUDE: 123° 26.7' W (-123.44564)
The bench mark is a disk set in a rock outcrop near the edge of the cliff over
the ocean, 26.84 m (88.1 ft) WSW of the center of the bottom of the stairs with
railing, 21.92 m (71.9 ft) SW of the SW corner of house, 7.99 m (26.2 ft) south
of STENGLE 2 RESET, 3.44 m (11.3 ft) north of edge of bluff and 0.19 m (0.6 ft)
higher than the ground.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 7
Station ID: 9416409 PUBLICATION DATE: 07/08/2013
Name: GREEN COVE, PACIFIC OCEAN
CA
NOAA Chart: 18640 Latitude: 38° 42.3' N ( 38.70433)
USGS Quad: STEWARTS POINT Longitude: 123° 27.0' W (-123.44939)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: STENGLE 2 1929 1961
DESIGNATION: STENGLE 2 RESET
MONUMENTATION: Triangulation Station disk VM#: 20635
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#:
SETTING CLASSIFICATION: Concrete OPUS PID:
LATITUDE: 38° 42.1' N ( 38.70094) LONGITUDE: 123° 26.7' W (-123.44561)
The bench mark is a disk set in concrete in a garden bed of ice plants, 27.74 m
(91.0 ft) west of the center of the bottom of the stairs with railings, 17.34 m
(56.9 ft) southwest of the southwest corner of the house, 8.53 m (28.0 ft) east
of the edge of the bluff, 7.99 m (26.2 ft) north of STENGLE 2 RM 2, 0.43 m (1.4
ft) west of a wooden post and about 0.12 m (0.4 ft) lower than the ground.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 6 of 7
Station ID: 9416409 PUBLICATION DATE: 07/08/2013
Name: GREEN COVE, PACIFIC OCEAN
CA
NOAA Chart: 18640 Latitude: 38° 42.3' N ( 38.70433)
USGS Quad: STEWARTS POINT Longitude: 123° 27.0' W (-123.44939)
T I D A L D A T U M S
Tidal datums at GREEN COVE, PACIFIC OCEAN based on:
LENGTH OF SERIES: 3 MONTHS
TIME PERIOD: December 2012 - February 2013
TIDAL EPOCH: 1983-2001
CONTROL TIDE STATION: 9416841 ARENA COVE, PACIFIC OCEAN
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
MEAN HIGHER HIGH WATER MHHW = 1.595
MEAN HIGH WATER MHW = 1.391
MEAN TIDE LEVEL MTL = 0.838
MEAN SEA LEVEL MSL = 0.813
MEAN LOW WATER MLW = 0.285
MEAN LOWER LOW WATER MLLW = 0.000
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
6409 B 2012 6.007 4.616
6409 A 2012 5.304 3.913
6409 C 2012 9.297 7.906
6409 D 2012 5.306 3.915
6409 E 2012 17.014 15.623
STENGLE 2 NO 2 1929 12.200 10.809
STENGLE 2 1929 1961 12.009 10.618
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 7 of 7
Station ID: 9416409 PUBLICATION DATE: 07/08/2013
Name: GREEN COVE, PACIFIC OCEAN
CA
NOAA Chart: 18640 Latitude: 38° 42.3' N ( 38.70433)
USGS Quad: STEWARTS POINT Longitude: 123° 27.0' W (-123.44939)
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 NGS's Integrated Data Base (IDB PID)
provides geodetic datum based on traditionally leveled and bluebooked ties to
the National Spatial Reference System(NSRS) https://www.ngs.noaa.gov/datasheets/.
The NGS Online Positioning User Service (OPUS PID) provides geodetic datum based
on GPS position & tie it to the NSRS https://www.ngs.noaa.gov/OPUS/.
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.