U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 7
Station ID: 8772471 PUBLICATION DATE: 05/10/2021
Name: FREEPORT SPIP, FREEPORT HARBOR
TX
NOAA Chart: 11330 Latitude: 28° 56.1' N ( 28.93570)
USGS Quad: FREEPORT Longitude: 95° 17.7' W ( -95.29420)
To reach the SPIP from the intersection of highway 332 and Fort Velasco Drive in
Surfside, Texas proceed southwest on Fort Velasco Drive For 1.59 km (0.99 mi)
then turn left onto Park View Road and proceed 0.29 km (0.18 mi) to surf drive
and make a right to proceed into Surfside Jetty Park. The bench marks are
located in the grassy area in the park and along the jetty walkway, and the SPIP
is located just west of the jetty.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 2447 A 2006
DESIGNATION: 877 2447 A TIDAL
ALIAS: 2447 A PBM
MONUMENTATION: Flange-encased Rod VM#: 22744
AGENCY: Conrad Blucher Institute (CBI) IDB PID:
SETTING CLASSIFICATION: Stainless steel rod OPUS PID#: BBGD50
LATITUDE: 28° 56.6' N ( 28.94333) LONGITUDE: 95° 18.2' W ( -95.30269)
The primary bench mark is a flange-encased rod located on the USCG Freeport
property, 9.6 m (31.5 ft) east along the driveway leading to the finger pier on
the southernmost side of the station, 1.67 m (5.48 ft) north of the fence on the
southernmost side of the station, and 0.72 m (2.4 ft) south of the southernmost
concrete driveway leading to the finger pier of the southernmost side of the
station adjacent to the Freeport Entrance Channel. The bench mark is set 0.1 m
(0.3 ft) below grade crimped to a stainless steel rod driven 13.4 m (44.0 ft) to
refusal, and is encased in a 0.60 m (1.97 ft) PVC pipe and concrete kickblock.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 7
Station ID: 8772471 PUBLICATION DATE: 05/10/2021
Name: FREEPORT SPIP, FREEPORT HARBOR
TX
NOAA Chart: 11330 Latitude: 28° 56.1' N ( 28.93570)
USGS Quad: FREEPORT Longitude: 95° 17.7' W ( -95.29420)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 2447 B 2006
DESIGNATION: 877 2447 B TIDAL
ALIAS: 2447 B
MONUMENTATION: Tidal Station disk VM#: 22745
AGENCY: Conrad Blucher Institute (CBI) IDB PID:
SETTING CLASSIFICATION: Retaining wall OPUS PID:
LATITUDE: 28° 56.6' N ( 28.94367) LONGITUDE: 95° 18.2' W ( -95.30278)
The bench mark is a disk set on top of the NW most point of the north retaining
wall of the boat ramp, 23.50m (77.1 ft) South of the South side of the USCG
office building, 17.20 m (56.4 ft) ENE of a concrete fuel tank, 0.42 m (1.38 ft)
east of the NW end of the retaining wall.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 7
Station ID: 8772471 PUBLICATION DATE: 05/10/2021
Name: FREEPORT SPIP, FREEPORT HARBOR
TX
NOAA Chart: 11330 Latitude: 28° 56.1' N ( 28.93570)
USGS Quad: FREEPORT Longitude: 95° 17.7' W ( -95.29420)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: USCG 1997
DESIGNATION: USCG
ALIAS: USCG
MONUMENTATION: Bench Mark disk VM#: 22747
AGENCY: US Coast and Geodetic Survey IDB PID:
SETTING CLASSIFICATION: Concrete monument OPUS PID#: BBGW03
LATITUDE: 28° 56.7' N ( 28.94444) LONGITUDE: 95° 18.2' W ( -95.30278)
The bench mark is a disk set on top of 0.3 m x 0.3 m (1.0 ft x 1.0 ft) concrete
monument, 31.00 m (101.7 ft) NE of the AC cooling unit at the NE corner of the
maintenance building, 30.60 m (100.4 ft) south of the north fence line, and 4.35
m (14.3 ft) NE of a radio supression antenna located NE of the maintenance
building, and 0.70 m (2.3 ft) above ground level.
BENCH MARK STAMPING: 2447 E 2006
DESIGNATION: 877 2447 E TIDAL
ALIAS: 2447 E
MONUMENTATION: Flange-encased Rod VM#: 22748
AGENCY: Conrad Blucher Institute (CBI) IDB PID#: DP0699
SETTING CLASSIFICATION: Stainless steel rod OPUS PID#: DP0699
LATITUDE: 28° 56.7' N ( 28.94481) LONGITUDE: 95° 18.2' W ( -95.30317)
The bench mark is flange-encased rod located on the property of the USCG
Freeport, 64.6 m (211.9 ft) north from bench mark 877 2447 C, 63.40 m (20.80 ft)
NNW of the USCG bench mark, and 8.22 m (27.0 ft) SW of the NW fence corner. The
datum point is set 0.1 m (0.3 ft) below grade crimped to a stainless steel rod
driven 14.2 m (46.6 ft) to refusal and encased in a 0.6 m (2.0 ft) PVC pipe with
a concrete kickblock.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 7
Station ID: 8772471 PUBLICATION DATE: 05/10/2021
Name: FREEPORT SPIP, FREEPORT HARBOR
TX
NOAA Chart: 11330 Latitude: 28° 56.1' N ( 28.93570)
USGS Quad: FREEPORT Longitude: 95° 17.7' W ( -95.29420)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 2447 A 2 2016
DESIGNATION: 877 2447 A 2
MONUMENTATION: Bench Mark disk VM#: 22751
AGENCY: National Ocean Service (NOS) IDB PID:
SETTING CLASSIFICATION: Concrete sidewalk OPUS PID:
LATITUDE: 28° 56.3' N ( 28.93756) LONGITUDE: 95° 17.7' W ( -95.29558)
The bench mark disk is located 18.3 m (60.0 ft) SSW of the first concrete light
pole coming from the jetty, 2.28 m (7.5 ft) east of a wooden hand rail on the
western edge of the jetty walk way, and 0.09 m (0.3 ft) SW of the eastern edge
of the concrete walk way.
BENCH MARK STAMPING: 2447 B 2 2016
DESIGNATION: 877 2447 B 2
MONUMENTATION: Flange-encased Rod VM#: 22752
AGENCY: National Ocean Service (NOS) IDB PID:
SETTING CLASSIFICATION: Stainless steel rod OPUS PID:
LATITUDE: 28° 56.3' N ( 28.93839) LONGITUDE: 95° 17.8' W ( -95.29614)
The bench mark is a stainless steel rod located 26.70 m (87.6 ft) NW of the
third wooden light pole from the jetty in the center of the park, 18.00 m (59.1
ft) NE of the fourth concrete light pole from the jetty on the western side of
the park, 11.40 m (37.4 ft) SW of the sidewalk running north to south along the
parking lot, and 9.00 m (29.5 ft) SSW of a witness post. The datum point is set
flush with the ground, being the top of a stainless steel rod driven 9.8 m (33.0
ft) to refusal and encased in a 5 inch NOS logo cap.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 7
Station ID: 8772471 PUBLICATION DATE: 05/10/2021
Name: FREEPORT SPIP, FREEPORT HARBOR
TX
NOAA Chart: 11330 Latitude: 28° 56.1' N ( 28.93570)
USGS Quad: FREEPORT Longitude: 95° 17.7' W ( -95.29420)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: RR 455 1951
DESIGNATION: RR 455
MONUMENTATION: Survey disk VM#: 22753
AGENCY: US Coast and Geodetic Survey IDB PID#: AM0093
SETTING CLASSIFICATION: Concrete block OPUS PID:
LATITUDE: 28° 56.5' N ( 28.94242) LONGITUDE: 95° 17.8' W ( -95.29650)
The benchmark is a disk set atop a concrete monument that is flush with the
ground located 15.00 m (49.2 ft) NNE of the centerline of Thunder Road, 8.00 m
(26.2 ft) ESE of the centerline of fort Velasco drive, 2.00 m (6.5 ft) NNW of a
red fire hydrant, and 0.85 m (2.8 ft) east of a witness post.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 6 of 7
Station ID: 8772471 PUBLICATION DATE: 05/10/2021
Name: FREEPORT SPIP, FREEPORT HARBOR
TX
NOAA Chart: 11330 Latitude: 28° 56.1' N ( 28.93570)
USGS Quad: FREEPORT Longitude: 95° 17.7' W ( -95.29420)
T I D A L D A T U M S
Tidal datums at FREEPORT SPIP, FREEPORT HARBOR based on:
LENGTH OF SERIES: 3 YEARS
TIME PERIOD: 07/2016-06/2018, 01/2019-12/2019
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 (08/27/2020) = 1.693
MEAN HIGHER HIGH WATER MHHW = 0.509
MEAN HIGH WATER MHW = 0.467
MEAN SEA LEVEL MSL = 0.277
MEAN TIDE LEVEL MTL = 0.276
North American Vertical Datum NAVD88 = 0.197
MEAN LOW WATER MLW = 0.086
MEAN LOWER LOW WATER MLLW = 0.000
LOWEST OBSERVED WATER LEVEL (12/21/2018) = -0.708
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
2447 A 2006 1.663 1.196
2447 B 2006 2.244 1.777
USCG 1997 2.839 2.372
2447 E 2006 1.887 1.420
2447 A 2 2016 2.792 2.325
2447 B 2 2016 2.709 2.242
RR 455 1951 1.365 0.898
Foot Notes:
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 7 of 7
Station ID: 8772471 PUBLICATION DATE: 05/10/2021
Name: FREEPORT SPIP, FREEPORT HARBOR
TX
NOAA Chart: 11330 Latitude: 28° 56.1' N ( 28.93570)
USGS Quad: FREEPORT Longitude: 95° 17.7' W ( -95.29420)
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.