Superseded Bench Mark Sheet for 9410962, BECHERS BAY, SANTA ROSA ISLAND CA

Present Epoch

Printable version

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
Datums Page                                                        Page  1 of  5

                                                   PUBLICATION DATE:  11/04/1995
Station ID: 9410962                                SUPERCEDED DATE:   04/21/2003
Name:       SANTA ROSA ISLAND, BECHERS BAY                    
            CALIFORNIA
NOAA Chart: 18728                                  Latitude:         34°  0.5' N
USGS Quad:  SANTA ROSA ISLAND NORTH                Longitude:       120°  2.8' W


To reach the tidal bench marks from Santa Barbara proceed by boat SW for about
38 statute miles (61 km) across Santa Barbara Channel to Santa Rosa Island and a
pier located at Bechers Bay about 2 miles (3 km) south of Carrington Point.  The
bench marks are on the ranch grounds adjacent to the pier.  The tide gauge and
staff were at the end of the pier.


                         T I D A L   B E N C H   M A R K S


                 PRIMARY BENCH MARK STAMPING:  1 1934

MONUMENTATION:           Survey Disk                               VM#:    11745
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Rock Outcrop


The primary bench mark is set in a drill hole on top of a large round shaped
outcrop of rock on the north slope of the first canyon north of the pier, about
50 feet (15 m) inshore from the mouth of the canyon.



                         BENCH MARK STAMPING:  4 1946

MONUMENTATION:           Survey Disk                               VM#:    11746
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Rock Outcrop


The bench mark is set in the top of a round shaped outcrop of rock on the south
slope of the first canyon north of the pier, about 184 feet (56 m) north of a
gate just east of the NE corner of the ranch foremans house, and 92 feet (28 m)
SSW of Bench Mark 1 1934.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  2 of  5

                                                   PUBLICATION DATE:  11/04/1995
Station ID: 9410962                                SUPERCEDED DATE:   04/21/2003
Name:       SANTA ROSA ISLAND, BECHERS BAY                    
            CALIFORNIA
NOAA Chart: 18728                                  Latitude:         34°  0.5' N
USGS Quad:  SANTA ROSA ISLAND NORTH                Longitude:       120°  2.8' W


                         T I D A L   B E N C H   M A R K S


                         BENCH MARK STAMPING:  0962 A 1977

MONUMENTATION:           Survey Disk                               VM#:    11747
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Galvanized Steel Rod


The bench mark is in the vicinity of the pier, about 250 feet  (76 m) SW of the
inshore end of the pier, about 102 feet (31 m) SW of the south end of a gate to
a gravel ramp leading to the  pier, 9 feet (3 m) SE of a wooden fence to a
cattle loading alley, and 2.8 feet (0.9 m) NE of a wire mesh fence.  The bench
mark is about 0.3 foot (0.1 m) below the ground, crimped to a galvanized steel
rod driven 22 feet (7 m) to refusal.



                         BENCH MARK STAMPING:  0962 B 1977

MONUMENTATION:           Survey Disk                               VM#:    11748
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Galvanized Steel Rod


The bench mark is in the vicinity of an old school house, about 427 feet (130 m)
WSW of the gate to the gravel ramp leading to the pier, 151 feet (46 m) east of
the SE corner and in line with the south face of the old school house (now used
as a separate bunk house), about 69 feet (21 m) south of the centerline of the
dirt road leading from the pier to the barns, 13 feet (4 m) west of a corner
post in a wooden fence, and 1.4 feet (0.4 m) north of an east-west corral fence.
The bench mark is about 0.3 foot (0.1 m) below the ground crimped to a
galvenized steel rod driven 7 feet (2 m) to refusal.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  3 of  5

                                                   PUBLICATION DATE:  11/04/1995
Station ID: 9410962                                SUPERCEDED DATE:   04/21/2003
Name:       SANTA ROSA ISLAND, BECHERS BAY                    
            CALIFORNIA
NOAA Chart: 18728                                  Latitude:         34°  0.5' N
USGS Quad:  SANTA ROSA ISLAND NORTH                Longitude:       120°  2.8' W


                         T I D A L   B E N C H   M A R K S


                         BENCH MARK STAMPING:  0962 C 1977

MONUMENTATION:           Survey Disk                               VM#:    11749
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Galvanized Steel Rod


The bench mark is near the ranch foremans house, about 367 feet (112 m) NW of a
gate to the gravel ramp leading to the pier, about 79 feet (24 m) SSW of the
west end of the gate located just east of the NE corner of the ranch foremans
house, 22.3 feet (6.8 m) east of the SE corner of the house and in line with the
front of the house, 16.9 feet (5.2 m) north of the SE yard fence corner, and 1.9
feet (0.6 m) east of the wooden yard fence. The bench mark is 0.3 foot (0.1 m)
below the ground crimped to a galvanized steel rod driven 6 feet (2 m) to
refusal.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  4 of  5

                                                   PUBLICATION DATE:  11/04/1995
Station ID: 9410962                                SUPERCEDED DATE:   04/21/2003
Name:       SANTA ROSA ISLAND, BECHERS BAY                    
            CALIFORNIA
NOAA Chart: 18728                                  Latitude:         34°  0.5' N
USGS Quad:  SANTA ROSA ISLAND NORTH                Longitude:       120°  2.8' W


                            T I D A L   D A T U M S 


Tidal datums at SANTA ROSA ISLAND, BECHERS BAY based on:

     LENGTH OF SERIES:      8 MONTHS
     TIME PERIOD:           OCT 1977-MAY 1978
     TIDAL EPOCH:           1960-1978
     CONTROL TIDE STATION:  9410660 LOS ANGELES


Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in FEET:

     HIGHEST OBSERVED WATER LEVEL (01/09/1978)         =   7.29
     MEAN HIGHER HIGH WATER                     MHHW   =   5.19
     MEAN HIGH WATER                            MHW    =   4.44
     MEAN TIDE LEVEL                            MTL    =   2.71
     MEAN LOW WATER                             MLW    =   0.99
     MEAN LOWER LOW WATER                       MLLW   =   0.00
     LOWEST  OBSERVED WATER LEVEL (12/11/1977)         =  -1.58



Bench Mark Elevation Information                In FEET above:

     Stamping or Designation                    MLLW        MHW

     1 1934                                     23.73     19.29
     4 1946                                     24.09     19.65
     0962 A 1977                                51.03     46.59
     0962 B 1977                                54.48     50.04
     0962 C 1977                                51.25     46.81


                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  5 of  5

                                                   PUBLICATION DATE:  11/04/1995
Station ID: 9410962                                SUPERCEDED DATE:   04/21/2003
Name:       SANTA ROSA ISLAND, BECHERS BAY                    
            CALIFORNIA
NOAA Chart: 18728                                  Latitude:         34°  0.5' N
USGS Quad:  SANTA ROSA ISLAND NORTH                Longitude:       120°  2.8' 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.

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