U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 6
Station ID: 8771165 PUBLICATION DATE: 10/29/2020
Name: GOAT ISLAND, SIEVERS COVE
TX
NOAA Chart: 11326 Latitude: 29° 25.9' N ( 29.43111)
USGS Quad: FLAKE Longitude: 94° 42.6' W ( -94.71042)
To reach from the U.S. Post Office at 2200 State Highway 87 in Port Bolivar,
Texas, head southwest on State Highway 87 for 8.3 km (5.2 mi) to Boyt Road, turn
right and continue northwest for 1.1 km (0.7 mi) to the 'T' intersection at W
Boyt Road, turn left and proceed west for 0.34 km (0.21 mi) to another 'T'
intersection, turn right and proceed 60 m (200 ft) to N Yacht Basin Road on the
left, turn left and follow the gravel track road for 76 m (250 ft) to a gate in
a chain link fence. The bench marks are located along south Rd and along State
Highway 87.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 1165 A 2019
DESIGNATION: 877 1165 A
MONUMENTATION: Flange-encased Rod VM#: 23256
AGENCY: National Ocean Service (NOS) IDB PID:
SETTING CLASSIFICATION: Stainless steel rod in sleeve OPUS PID#: BBGS06
LATITUDE: 29° 25.9' N ( 29.43111) LONGITUDE: 94° 42.6' W ( -94.70931)
The primary bench mark is a flange encased rod set in the grass to the N of N
yacht basin road, 22.13 m (72.6 ft) NE of a fence corner at the NW corner of an
RV park, 19.65 m (64.5 ft) NW of a power pole, 8.05 m (26.4 ft) N of the
centerline of N Yacht basin road, 6.84 m (22.4 ft) S of the SE corner of a boat
shed and 6.02 m (19.8 ft) SE of a short power pole with a meter box. The datum
point is set 5 cm (2 inches) below the ground, being the top of a stainless
steel rod driven 28.04 m (92.0 ft) to refusal and encased in a 7.25-in (18 cm)
NOS logo cap with concrete kick block.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 6
Station ID: 8771165 PUBLICATION DATE: 10/29/2020
Name: GOAT ISLAND, SIEVERS COVE
TX
NOAA Chart: 11326 Latitude: 29° 25.9' N ( 29.43111)
USGS Quad: FLAKE Longitude: 94° 42.6' W ( -94.71042)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING:
DESIGNATION: PAM 49 ARP
MONUMENTATION: See descriptive text VM#: 23254
AGENCY: IDB PID#: DM7900
SETTING CLASSIFICATION: Galvanized steel pipe in sleeve OPUS PID:
LATITUDE: 29° 25.3' N ( 29.42244) LONGITUDE: 94° 42.1' W ( -94.70153)
The bench mark is a CORS station set along the northern side of state highway
87, 22.80 m (74.8 ft) NE of a power pole, 5.66 m (18.6 ft) S of a fence corner,
4.22 m (13.8 ft) SW of where the fence line runs SE to NW and 3.60 m (11.8 ft)
SE of where the fence line runs NE to SW.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 6
Station ID: 8771165 PUBLICATION DATE: 10/29/2020
Name: GOAT ISLAND, SIEVERS COVE
TX
NOAA Chart: 11326 Latitude: 29° 25.9' N ( 29.43111)
USGS Quad: FLAKE Longitude: 94° 42.6' W ( -94.71042)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: LEAS RESET 2008 USACE
DESIGNATION: LEAS RESET
MONUMENTATION: Survey disk VM#: 23255
AGENCY: US Army CORPS of Engineers (USACE) IDB PID:
SETTING CLASSIFICATION: Concrete monument OPUS PID#: BBGS04
LATITUDE: 29° 25.8' N ( 29.43061) LONGITUDE: 94° 42.5' W ( -94.70894)
The bench mark is a disk along a gravel drive NW of the intersection of W Boyt
road and Boyt road, 26.25 m (86.1 ft) WSW of a power pole, 13.91 m (45.6 ft) NNW
of the western corner of a boat shed, 7.05 m (23.1 ft) N of the centerline of
the gravel driveway, 1.35 m (4.4 ft) SE of a power pole and 0.77 m (2.5 ft) S of
a Carsonite post.
BENCH MARK STAMPING: 1165 B 2019
DESIGNATION: 877 1165 B
MONUMENTATION: Tidal Station disk VM#: 23257
AGENCY: National Ocean Service (NOS) IDB PID:
SETTING CLASSIFICATION: Concrete slab OPUS PID:
LATITUDE: 29° 25.8' N ( 29.43061) LONGITUDE: 94° 42.6' W ( -94.71003)
The bench mark is a disk set in concrete to the S of N Yacht basin road, 36.75 m
(120.6 ft) SW of a power pole, 30.1 m (98.8 ft) SSE of a concrete dock, 19.15 m
(62.8 ft) N of a piling at an angled point in a dock and 13.42 m (44.0 ft) N of
a steel sign post, 11.41 m (37.4 ft) N from a power pole and 8.82 m (28.9 ft) NW
from a building corner.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 6
Station ID: 8771165 PUBLICATION DATE: 10/29/2020
Name: GOAT ISLAND, SIEVERS COVE
TX
NOAA Chart: 11326 Latitude: 29° 25.9' N ( 29.43111)
USGS Quad: FLAKE Longitude: 94° 42.6' W ( -94.71042)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 1165 C 2019
DESIGNATION: 877 1165 C
MONUMENTATION: Flange-encased Rod VM#: 23258
AGENCY: National Ocean Service (NOS) IDB PID:
SETTING CLASSIFICATION: Stainless steel rod in sleeve OPUS PID#: BBGS05
LATITUDE: 29° 25.4' N ( 29.42292) LONGITUDE: 94° 41.9' W ( -94.69900)
The bench mark is a flange encased rod set in the grass E of the intersection of
state highway 87 and Boyt road, 36.68 m (120.3 ft) SSE of a fence corner, 19.02
m (62.4 ft) SSE of the centerline of state highway 87, 17.65 m (57.9 ft) NE of a
power pole with a street lamp, 16.61 m (54.5 ft) SW of a power pole along state
highway 87, 13.81 m (45.3 ft) NE of the NE corner of a concrete pedestal and
8.25 m (27.1 ft) NE of the centerline of Boyt road. The datum point is set 5 cm
(2 inches) below ground, being the top of a stainless steel rod driven 27.13 m
(89.0 ft) to refusal and encased in a 7.25-in (18 cm) NOS logo cap with concrete
kick block.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 6
Station ID: 8771165 PUBLICATION DATE: 10/29/2020
Name: GOAT ISLAND, SIEVERS COVE
TX
NOAA Chart: 11326 Latitude: 29° 25.9' N ( 29.43111)
USGS Quad: FLAKE Longitude: 94° 42.6' W ( -94.71042)
T I D A L D A T U M S
Tidal datums at GOAT ISLAND, SIEVERS COVE based on:
LENGTH OF SERIES: 3 MONTHS
TIME PERIOD: December 2019 - February 2020
TIDAL EPOCH: 1983-2001
CONTROL TIDE STATION: 8771013 EAGLE POINT, GALVESTON BAY
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
MEAN HIGHER HIGH WATER MHHW = 0.353
MEAN HIGH WATER MHW = 0.330
MEAN SEA LEVEL MSL = 0.200
MEAN TIDE LEVEL MTL = 0.176
North American Vertical Datum NAVD88 = 0.129
MEAN LOW WATER MLW = 0.022
MEAN LOWER LOW WATER MLLW = 0.000
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
1165 A 2019 1.413 1.083
PAM 49 ARP 2.767 2.437
LEAS RESET 2008 USACE 1.225 0.895
1165 B 2019 1.518 1.188
1165 C 2019 2.680 2.350
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 6 of 6
Station ID: 8771165 PUBLICATION DATE: 10/29/2020
Name: GOAT ISLAND, SIEVERS COVE
TX
NOAA Chart: 11326 Latitude: 29° 25.9' N ( 29.43111)
USGS Quad: FLAKE Longitude: 94° 42.6' W ( -94.71042)
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.