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.