NOAA Web Site Link Tides and Currents Home Page Transparent placeholder image

Bench Mark Sheet for 8666799, DAWHOO BRIDGE, DAWHOO RIVER SC

Superseded Epoch

Large map location marker Station Location
Small red map location marker Published bench mark
Small blue map location marker Unpublished bench mark

Bench mark positions only appear on the map if their coordinates in the CO-OPS database are at the precision of degrees/minutes/seconds/and tenths of seconds. If the coordinates are less precise, the mark will not appear.

Printable version

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
Datums Page                                                        Page  1 of  6

                                                                                
Station ID: 8666799                         PUBLICATION DATE:  04/21/2010
Name:       DAWHOO BRIDGE, DAWHOO RIVER                       
            SC
NOAA Chart: 11517                           Latitude:   32° 38.2' N (  32.63670)
USGS Quad:  ADAMS RUN                       Longitude:  80° 20.5' W ( -80.34170)


To reach the tidal bench marks from the Post Office in Edisto Island, proceed
north on State Highway 174 for 10.6 km (6.6 mi) to the old concrete bridge over
Dawhoo River, now a fishing pier.  The bench marks are on the pier and in the
adjacent parking lot.  The tide gage and staff were on a pier just east of the
old bridge.


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


                 PRIMARY BENCH MARK STAMPING:  6799 F 1993
                         DESIGNATION:          866 6799 F TIDAL

MONUMENTATION:           Tidal Station disk                    VM#:        17068
AGENCY:                  National Ocean Service (NOS)          IDB PID#:  AE2766
SETTING CLASSIFICATION:  Bridge deck                           OPUS PID#: AE2766
LATITUDE:   32° 37.9' N (  32.63170)          LONGITUDE:  80° 20.5' W ( -80.34170)


The primary bench mark is a disk set in the deck of the old bridge, 1.13 m (3.7
ft) west of the NW leg of the sign for McKinley Washington Jr. Bridge, 0.3 m
(1.0 ft) NE of the SW edge of the concrete deck of the bridge, and 0.09 m (0.3
ft) WNW of the NW edge of the concrete rail of the bridge.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  2 of  6

                                                                                
Station ID: 8666799                         PUBLICATION DATE:  04/21/2010
Name:       DAWHOO BRIDGE, DAWHOO RIVER                       
            SC
NOAA Chart: 11517                           Latitude:   32° 38.2' N (  32.63670)
USGS Quad:  ADAMS RUN                       Longitude:  80° 20.5' W ( -80.34170)


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


                         BENCH MARK STAMPING:  S 109 1962
                         DESIGNATION:          S 109

MONUMENTATION:           Bench Mark disk                       VM#:         6657
AGENCY:                  US Coast and Geodetic Survey
                         (USC&GS)                              IDB PID#:  CK1760
SETTING CLASSIFICATION:  Concrete abutment                     OPUS PID:        
LATITUDE:   32° 38.3' N (  32.63830)          LONGITUDE:  80° 20.5' W ( -80.34170)


The bench mark is a disk set flush in the concrete abutment on the NE corner of
the bridge, 4.57 m (15.6 ft) east of the centerline of State Highway 174, 3.41 m
(11.2 ft) SSW of power pole #244116, 0.94 m (3.1 ft) east of the curb on the NE
corner of the bridge, and 0.12 m (0.4 ft) west of the east edge of the bridge
abutment.  



                         BENCH MARK STAMPING:  6799 C 1977
                         DESIGNATION:          866 6799 C TIDAL

MONUMENTATION:           Bench Mark disk                       VM#:         6659
AGENCY:                  National Ocean Survey (NOS)           IDB PID#:  CK1761
SETTING CLASSIFICATION:  Concrete bridge abutment              OPUS PID#: CK1761
LATITUDE:   32° 38.1' N (  32.63500)          LONGITUDE:  80° 20.5' W ( -80.34170)


The bench mark is a disk in the concrete bridge abutment on the SW corner of the
old concrete bridge, now a fishing pier, 4.02 m (13.2 ft) WSW of the centerline
of State Highway 174, and 0.27 m (0.9 ft) north of the south edge of the bridge
abutment.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  3 of  6

                                                                                
Station ID: 8666799                         PUBLICATION DATE:  04/21/2010
Name:       DAWHOO BRIDGE, DAWHOO RIVER                       
            SC
NOAA Chart: 11517                           Latitude:   32° 38.2' N (  32.63670)
USGS Quad:  ADAMS RUN                       Longitude:  80° 20.5' W ( -80.34170)


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


                         BENCH MARK STAMPING:  R 109 1962
                         DESIGNATION:          R 109

MONUMENTATION:           Bench Mark disk                       VM#:        17069
AGENCY:                  US Coast and Geodetic Survey
                         (USC&GS)                              IDB PID#:  CK1758
SETTING CLASSIFICATION:  Concrete post                         OPUS PID:        
LATITUDE:   32° 39.3' N (  32.65500)          LONGITUDE:  80° 20.6' W ( -80.34330)


The bench mark is a disk set in a concrete post, 43.2 m (141.7 ft) SSE of a
power pole number 297779 across the highway, 15.7 m (51.6 ft) ESE of the center
of the highway, 11.9 m (38.9 ft) east of a 5.0-foot multi-trunked live oak tree,
2.0 m (6.6 ft) NW of a 1.3-foot pine tree with a SCGS reference washer attached,
0.6 m (1.9 ft) south of a witness post, and level with the highway.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  4 of  6

                                                                                
Station ID: 8666799                         PUBLICATION DATE:  04/21/2010
Name:       DAWHOO BRIDGE, DAWHOO RIVER                       
            SC
NOAA Chart: 11517                           Latitude:   32° 38.2' N (  32.63670)
USGS Quad:  ADAMS RUN                       Longitude:  80° 20.5' W ( -80.34170)


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


                         BENCH MARK STAMPING:  M 143 1979
                         DESIGNATION:          M 143

MONUMENTATION:           Vertical Control disk                 VM#:        17070
AGENCY:                  National Geodetic Survey (NGS)        IDB PID#:  CK1759
SETTING CLASSIFICATION:  Galvanized steel rod                  OPUS PID:        
LATITUDE:   32° 39.1' N (  32.65170)          LONGITUDE:  80° 20.7' W ( -80.34500)


The bench mark is a disk located 16.8 m (55.0 ft) west of the center of the
highway, 5.2 m (17.0 ft) NNW of power pole number 307650 with three guy wires,
and 0.9 m (3.0 ft) north of a witness post.  The bench mark is set 0.3 m (1.0
ft) below the highway, and crimped to the top of a galvanized steel rod driven
7.3 m (23.9 ft).

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  5 of  6

                                                                                
Station ID: 8666799                         PUBLICATION DATE:  04/21/2010
Name:       DAWHOO BRIDGE, DAWHOO RIVER                       
            SC
NOAA Chart: 11517                           Latitude:   32° 38.2' N (  32.63670)
USGS Quad:  ADAMS RUN                       Longitude:  80° 20.5' W ( -80.34170)


                            T I D A L   D A T U M S 


Tidal datums at DAWHOO BRIDGE, DAWHOO RIVER based on:

     LENGTH OF SERIES:      1 YEAR
     TIME PERIOD:           May 1977 - April 1978
     TIDAL EPOCH:           1983-2001
     CONTROL TIDE STATION:  8665530 CHARLESTON, COOPER RIVER ENTRANCE


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

     HIGHEST OBSERVED WATER LEVEL (06/01/1977)         =  2.535
     MEAN HIGHER HIGH WATER                     MHHW   =  2.049
     MEAN HIGH WATER                            MHW    =  1.943
     MEAN SEA LEVEL                             MSL    =  1.113
     North American Vertical Datum              NAVD88 =  1.107
     MEAN TIDE LEVEL                            MTL    =  1.003
     MEAN LOW WATER                             MLW    =  0.064
     MEAN LOWER LOW WATER                       MLLW   =  0.000
     LOWEST  OBSERVED WATER LEVEL (01/09/1978)         = -0.897

North American Vertical Datum (NAVD88)

Bench Mark Elevation Information                In METERS above:

     Stamping or Designation                    MLLW        MHW

     6799 F 1993                                 4.440    2.497
     S 109 1962                                  4.252    2.309
     6799 C 1977                                 4.317    2.374
     R 109 1962                                  2.942    0.999
     M 143 1979                                  3.553    1.610


Foot Notes:

Bench marks 6799 F 1993, M 143 1979, and R 109 1962 are based on one
differential leveling connection and do not meet the quality control standards
of the NOS.  Therefore, caution should be used when deriving elevations for
these marks.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  6 of  6

                                                                                
Station ID: 8666799                         PUBLICATION DATE:  04/21/2010
Name:       DAWHOO BRIDGE, DAWHOO RIVER                       
            SC
NOAA Chart: 11517                           Latitude:   32° 38.2' N (  32.63670)
USGS Quad:  ADAMS RUN                       Longitude:  80° 20.5' W ( -80.34170)


                             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.

Return to Top
Products available at 8666799 DAWHOO BRIDGE, DAWHOO RIVER, SC

Revised: 08/08/2018
NOAA / National Ocean Service
Web site owner: Center for Operational Oceanographic Products and Services