Bench Mark Sheet for 8771486, Galveston Railroad Bridge TX

Superseded Epoch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Small blue map location marker Unpublished bench mark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: 8771486                         PUBLICATION DATE:  05/04/2020
Name:       GALVESTON RAILROAD BRIDGE                         
            TX
NOAA Chart: 11324                           Latitude:   29° 18.2' N (  29.30260)
USGS Quad:  VIRGINIA POINT                  Longitude:  94° 53.8' W ( -94.89710)


From Galveston, head north on I-45.  Take Exit 4 toward Village of Tiki Island,
then turn right on Virginia Point Rd.  Follow the railroad, there will be a road
that parallels the track, follow that to get to the station which is located
about a quarter mile towards Galveston on the railroad bridge.  The station is a
four pile platform, accessible from the railroad bridge.  before driving out to
station, contact railroad at 713-304-5962 in advance.


                         T I D A L   B E N C H   M A R K S
                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  2 of  6

                                                                                
Station ID: 8771486                         PUBLICATION DATE:  05/04/2020
Name:       GALVESTON RAILROAD BRIDGE                         
            TX
NOAA Chart: 11324                           Latitude:   29° 18.2' N (  29.30260)
USGS Quad:  VIRGINIA POINT                  Longitude:  94° 53.8' W ( -94.89710)


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


                 PRIMARY BENCH MARK STAMPING:  L305 1935
                         DESIGNATION:          L305 1935

MONUMENTATION:           Survey disk                           VM#:        20684
AGENCY:                  Unknown                               IDB PID#:  AW0467
SETTING CLASSIFICATION:  Concrete abutment                     OPUS PID:        
LATITUDE:   29° 18.2' N (  29.30372)          LONGITUDE:  94° 53.9' W ( -94.89886)


The primary bench mark is a disk set flush into a concrete abutment at the end
of the the railroad bridge, located 189.3 m (621.1 ft) SE of P1210 1973, 78.7 m
(258.2 ft) NW of 1486 B 2012, and 42.5 m (139.4 ft) SE of 1486 C 2012.  



                         BENCH MARK STAMPING:  1486 A 2012
                         DESIGNATION:          877 1486 A

MONUMENTATION:           Survey disk                           VM#:        20682
AGENCY:                  Division of Nearshore Reseach         IDB PID:         
SETTING CLASSIFICATION:  Road                                  OPUS PID:        
LATITUDE:   29° 18.2' N (  29.30278)          LONGITUDE:  94° 53.8' W ( -94.89733)


The bench mark is a disk set in the roadway next to the railroad tracks, located
175.6 m (576.1 ft) SE of L305 1935, 98.22 m (322.2 ft) SE of 1486 B 2012, and
88.3 m (289.7 ft) NW of the tide station.

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

                                                                                
Station ID: 8771486                         PUBLICATION DATE:  05/04/2020
Name:       GALVESTON RAILROAD BRIDGE                         
            TX
NOAA Chart: 11324                           Latitude:   29° 18.2' N (  29.30260)
USGS Quad:  VIRGINIA POINT                  Longitude:  94° 53.8' W ( -94.89710)


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


                         BENCH MARK STAMPING:  1486 B 2012
                         DESIGNATION:          877 1486 B

MONUMENTATION:           Survey disk                           VM#:        20683
AGENCY:                  Division of Nearshore Research        IDB PID:         
SETTING CLASSIFICATION:  Road                                  OPUS PID:        
LATITUDE:   29° 18.2' N (  29.30322)          LONGITUDE:  94° 53.9' W ( -94.89822)


The bench is a disk set in the roadway next to the railroad tracks located 187.3
m (614.5 ft) NW of the tide station, 120.30 m (394.7 ft) SE of bench mark 1486 C
2012, and 75.10 m (246.4 ft) SE of bench mark L 305.



                         BENCH MARK STAMPING:  1486 C 2012
                         DESIGNATION:          877 1486 C

MONUMENTATION:           Flange-encased Rod                    VM#:        20686
AGENCY:                  Unknown                               IDB PID#:  DO9997
SETTING CLASSIFICATION:  Deep Rod                              OPUS PID#: DO9997
LATITUDE:   29° 18.2' N (  29.30400)          LONGITUDE:  94° 53.9' W ( -94.89911)


The bench mark is a stainless steel rod located 148.90 m (488.5 ft) ESE of bench
mark P 1210 1973, 119.90 m (393.4 ft) NW of bench mark 1486 B 2012, 42.30 m
(138.8 ft) NW of bench mark L 305 1935, driven to a depth of 13.5 m, and encased
in a 6 inch (15 cm) PVC pipe with concrete kick block.

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

                                                                                
Station ID: 8771486                         PUBLICATION DATE:  05/04/2020
Name:       GALVESTON RAILROAD BRIDGE                         
            TX
NOAA Chart: 11324                           Latitude:   29° 18.2' N (  29.30260)
USGS Quad:  VIRGINIA POINT                  Longitude:  94° 53.8' W ( -94.89710)


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


                         BENCH MARK STAMPING:  P 1210 1973
                         DESIGNATION:          P 1210 1973

MONUMENTATION:           Vertical Control disk                 VM#:        20933
AGENCY:                  National Geodetic Survey (NGS)        IDB PID#:  AW0468
SETTING CLASSIFICATION:  Copper-clad steel rod in sleeve       OPUS PID:        
LATITUDE:   29° 18.3' N (  29.30450)          LONGITUDE:  94° 54.0' W ( -94.90056)


The bench mark is a disk on the top of a 16 mm (5/8 inch) copper coated rod. 
The bench mark is located 0.2 km (0.1 mi) NW of the NW end of the railroad
bridge over Galveston Bay and bench mark l 305, 6.3 m (20.7 ft) SW of the SW
rail of the main track, 18.6 m (61.0 ft) SW and across the track from the west
corner of the tower, 10.1 m (33 ft) NE of the center line of a concrete access
road, 17.4 m (57 ft) southeast of a railroad signal, 0.3 m  (1 ft) NE of power
pole 74, 0.4 m (1.3 ft) SW of a witness post.  The bench mark is driven to
gradual refusal at a depth of 12.2 m (40 ft) and the upper portion of the rod is
encased in a concrete post projection 0.03 m (0.1 ft) above the ground.

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

                                                                                
Station ID: 8771486                         PUBLICATION DATE:  05/04/2020
Name:       GALVESTON RAILROAD BRIDGE                         
            TX
NOAA Chart: 11324                           Latitude:   29° 18.2' N (  29.30260)
USGS Quad:  VIRGINIA POINT                  Longitude:  94° 53.8' W ( -94.89710)


                            T I D A L   D A T U M S 


Tidal datums at GALVESTON RAILROAD BRIDGE based on:

     LENGTH OF SERIES:      3 YEARS
     TIME PERIOD:           10/13-9/14, 5/16-4/18
     TIDAL EPOCH:           1983-2001
     CONTROL TIDE STATION:  8771450 GALVESTON PIER 21, GALVESTON CHANNEL


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

     HIGHEST OBSERVED WATER LEVEL (10/25/2018)         =  1.246
     MEAN HIGHER HIGH WATER                     MHHW   =  0.386
     MEAN HIGH WATER                            MHW    =  0.362
     MEAN SEA LEVEL                             MSL    =  0.228
     MEAN TIDE LEVEL                            MTL    =  0.212
     North American Vertical Datum              NAVD88 =  0.106
     MEAN LOW WATER                             MLW    =  0.062
     MEAN LOWER LOW WATER                       MLLW   =  0.000
     LOWEST  OBSERVED WATER LEVEL (12/21/2018)         = -0.821

North American Vertical Datum (NAVD88)

Bench Mark Elevation Information                In METERS above:

     Stamping or Designation                    MLLW        MHW

     L305 1935                                   4.071    3.709
     1486 A 2012                                 4.718    4.356
     1486 B 2012                                 4.726    4.364
     1486 C 2012                                 3.728    3.366
     P 1210 1973                                 4.031    3.669


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

                                                                                
Station ID: 8771486                         PUBLICATION DATE:  05/04/2020
Name:       GALVESTON RAILROAD BRIDGE                         
            TX
NOAA Chart: 11324                           Latitude:   29° 18.2' N (  29.30260)
USGS Quad:  VIRGINIA POINT                  Longitude:  94° 53.8' W ( -94.89710)


                             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.

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