Superseded Bench Mark Sheet for 8664992, NORTH DEWEES ISLAND SC

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:  01/06/1988
Station ID: 8664992                                SUPERCEDED DATE:   04/21/2003
Name:       NORTH DEWEES ISLAND, CAPERS INLET                 
            SOUTH CAROLINA
NOAA Chart: 11521                                  Latitude:         32° 51.0' N
USGS Quad:  CAPERS INLET                           Longitude:        79° 42.2' W


To reach the tidal bench marks proceed by boat to the NE end of Dewees Island in
Capers Inlet.  The bench marks are located along a dirt road leading south from
the shoreline of Capers Inlet.  The tide gage and staff were located near the NE
corner of the pier at the north end of the dirt road.


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


                 PRIMARY BENCH MARK STAMPING:  N.D.I. NO 1 1975

MONUMENTATION:           Survey Disk                               VM#:     4124
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Copper-clad Steel Rod


The bench mark is located in a small group of cedar trees at the north end of
Dewees Island, 61.5 feet (18.7 m) SSE of the SE corner of a wooden pier, 20 feet
(6 m) east of the centerline of the dirt road, 2.3 feet (0.7 m) NE of a metal
witness post with sign, and 2.1 feet (0.6 m) ESE of a second witness post with
sign.  The bench mark is 0.1 foot (0.03 m) below ground level, crimped to a
copper-clad steel rod driven to an unspecified depth, and encased in a PVC pipe
and concrete kickblock.



                         BENCH MARK STAMPING:  N.D.I. NO 2 1975

MONUMENTATION:           Survey Disk                               VM#:     4125
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Copper-clad Steel Rod


The bench mark is 150.1 feet (45.8 m) south of Bench Mark N.D.I. NO 1 1975, 12.4
feet (3.8 m) east of the centerline of the dirt road, and 1.4 feet      (0.4 m)
SE of a witness post with sign.  The bench mark is crimped to a copper-clad
steel rod driven to an unspecified depth, and encased in a PVC pipe and concrete
kickblock.

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

                                                   PUBLICATION DATE:  01/06/1988
Station ID: 8664992                                SUPERCEDED DATE:   04/21/2003
Name:       NORTH DEWEES ISLAND, CAPERS INLET                 
            SOUTH CAROLINA
NOAA Chart: 11521                                  Latitude:         32° 51.0' N
USGS Quad:  CAPERS INLET                           Longitude:        79° 42.2' W


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


                         BENCH MARK STAMPING:  N.D.I. NO 3 1975

MONUMENTATION:           Survey Disk                               VM#:     4126
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Copper-clad Steel Rod


The bench mark is 125.0 feet (38.1 m) south of Bench Mark N.D.I. NO 2 1975, 12.3
feet (3.7 m) east of the centerline of the dirt road, 3.2 feet (1.0 m) north of
a steel witness post with sign, and 2.5 feet (0.8 m) ESE of a second witness
post with sign.  The bench mark is at ground level, crimped to a copper-clad
steel rod driven to an unspecified depth, and encased in a PVC pipe and concrete
kickblock.



                         BENCH MARK STAMPING:  N.D.I. NO 4 1975

MONUMENTATION:           Survey Disk                               VM#:     4127
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Copper Pipe


The bench mark is 76 feet (23 m) SSE of Bench Mark N.D.I. NO 3 1975, 17.2 feet
(5.2 m) east of the centerline of the dirt road, and 2.6 feet (0.8 m) east of a
witness post with sign.  The bench mark is 0.5 foot (0.2 m) above ground level,
brazed to the top of a copper pipe surrounded by a 1.2-foot (0.4 m) diameter
concrete kickblock.

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

                                                   PUBLICATION DATE:  01/06/1988
Station ID: 8664992                                SUPERCEDED DATE:   04/21/2003
Name:       NORTH DEWEES ISLAND, CAPERS INLET                 
            SOUTH CAROLINA
NOAA Chart: 11521                                  Latitude:         32° 51.0' N
USGS Quad:  CAPERS INLET                           Longitude:        79° 42.2' W


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


                         BENCH MARK STAMPING:  N.D.I. NO 5 1975

MONUMENTATION:           Survey Disk                               VM#:     4128
AGENCY:                                                            PID:         
SETTING CLASSIFICATION:  Copper Pipe


The bench mark is 151.4 feet (46.1 m) south of Bench Mark N.D.I. NO 4 1975, 11.8
feet (3.6 m) east of the centerline of the dirt road, 1.8 feet (0.5 m) north of
a steel witness post with sign, and 1.3 feet (0.4 m) west of a second witness
post with sign.  The bench mark is 0.5 foot (0.2 m) above ground level, brazed
to the top of a copper pipe surrounded by a 1.1-foot (0.3 m) diameter concrete
kickblock.

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

                                                   PUBLICATION DATE:  01/06/1988
Station ID: 8664992                                SUPERCEDED DATE:   04/21/2003
Name:       NORTH DEWEES ISLAND, CAPERS INLET                 
            SOUTH CAROLINA
NOAA Chart: 11521                                  Latitude:         32° 51.0' N
USGS Quad:  CAPERS INLET                           Longitude:        79° 42.2' W


                            T I D A L   D A T U M S 


Tidal datums at NORTH DEWEES ISLAND, CAPERS INLET based on:

     LENGTH OF SERIES:      3 MONTHS
     TIME PERIOD:           OCTOBER-DECEMBER 1975
     TIDAL EPOCH:           1960-1978
     CONTROL TIDE STATION:  8664941 CAPERS CREEK


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

     HIGHEST OBSERVED WATER LEVEL (10/05/1975)         =   6.81
     MEAN HIGHER HIGH WATER                     MHHW   =   5.35
     MEAN HIGH WATER                            MHW    =   5.01
     MEAN TIDE LEVEL                            MTL    =   2.61
     MEAN LOW WATER                             MLW    =   0.20
     MEAN LOWER LOW WATER                       MLLW   =   0.00
     LOWEST  OBSERVED WATER LEVEL (12/28/1975)         =  -0.73



Bench Mark Elevation Information                In FEET above:

     Stamping or Designation                    MLLW        MHW

     N.D.I. NO 1 1975                            8.93      3.92
     N.D.I. NO 2 1975                            7.89      2.88
     N.D.I. NO 3 1975                            8.10      3.09
     N.D.I. NO 4 1975                           10.19      5.18
     N.D.I. NO 5 1975                            8.71      3.70


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

                                                   PUBLICATION DATE:  01/06/1988
Station ID: 8664992                                SUPERCEDED DATE:   04/21/2003
Name:       NORTH DEWEES ISLAND, CAPERS INLET                 
            SOUTH CAROLINA
NOAA Chart: 11521                                  Latitude:         32° 51.0' N
USGS Quad:  CAPERS INLET                           Longitude:        79° 42.2' 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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