U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 5
Station ID: 8724409 PUBLICATION DATE: 11/13/2003
Name: INNER NARROWS
FL
NOAA Chart: 11445 Latitude: 24° 39.5' N ( 24.65830)
USGS Quad: SUGARLOAF KEY Longitude: 81° 36.5' W ( -81.60830)
To reach the tidal bench marks by boat from the public boat ramp at the Boca
Chica Channel bridge, proceed NE for 14.5 km (9.0 statute mi) to the SE end of
the Snipe Keys and the channel known as Inner Narrows. The bench marks are
located on a small island on the SE side of Inner Narrows. The tide gage and
staff were located offshore of the SE end of Snipe Keys on the NW side of Inner
Narrows.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: DUG RM 1 1934
DESIGNATION: 872 4409 DUG RM 1
MONUMENTATION: Reference Mark disk VM#: 9579
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#: AE4418
SETTING CLASSIFICATION: Concrete monument OPUS PID:
LATITUDE: 24° 39.5' N ( 24.65830) LONGITUDE: 81° 36.5' W ( -81.60830)
The primary bench mark is a disk set in a square concrete monument, 14.51 m
(47.6 ft) east of the broken concrete monument for former Triangulation Station
DUG 1934 which was located 80 m (262 ft) west of the east end of the island and
6 m (20 ft) south of the north bank, 0.12 m (0.4 ft) west of a witness post, and
0.09 m (1.0 ft) above ground level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 5
Station ID: 8724409 PUBLICATION DATE: 11/13/2003
Name: INNER NARROWS
FL
NOAA Chart: 11445 Latitude: 24° 39.5' N ( 24.65830)
USGS Quad: SUGARLOAF KEY Longitude: 81° 36.5' W ( -81.60830)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: NO 4 1974
DESIGNATION: 872 4409 TIDAL 4
MONUMENTATION: Tidal Station disk VM#: 9580
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Concrete monument OPUS PID:
LATITUDE: 24° 39.5' N ( 24.65830) LONGITUDE: 81° 36.5' W ( -81.60830)
The bench mark is a disk set in a concrete monument atop a copper-clad steel rod
driven to refusal on a sand berm, 16.25 m (53.3 ft) NE of Bench Mark NO 5 1974,
10.21 m (33.5 ft) SW of Bench Mark 4409 F 1984, 0.40 m (1.3 ft) NW of an old
witness post, 0.21 m (0.7 ft) NW of a new witness post, and 0.09 m (0.3 ft)
above ground level.
BENCH MARK STAMPING: NO 5 1974
DESIGNATION: 872 4409 TIDAL 5
MONUMENTATION: Tidal Station disk VM#: 9581
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Concrete monument OPUS PID:
LATITUDE: 24° 39.5' N ( 24.65830) LONGITUDE: 81° 36.5' W ( -81.60830)
The bench mark is a disk set in a concrete monument atop a copper-clad steel rod
driven to refusal on the edge of a sand berm, 17 m (55 ft) west of the eastern
outer mangrove fringe, 8 m (25 ft) east of the western outer mangrove fringe,
0.61 m (2.0 ft) NW of an old witness post, and 0.30 m (1.0 ft) SW of a new
witness post.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
Station ID: 8724409 PUBLICATION DATE: 11/13/2003
Name: INNER NARROWS
FL
NOAA Chart: 11445 Latitude: 24° 39.5' N ( 24.65830)
USGS Quad: SUGARLOAF KEY Longitude: 81° 36.5' W ( -81.60830)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 4409 F 1984
DESIGNATION: 872 4409 F TIDAL
MONUMENTATION: Tidal Station disk VM#: 9582
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Concrete monument OPUS PID:
LATITUDE: 24° 39.5' N ( 24.65830) LONGITUDE: 81° 36.5' W ( -81.60830)
The bench mark is a disk set in the concrete monument of former Bench Mark DUG
RM 2 1934, 13.66 m (44.8 ft) SW of Bench Mark 4409 G 1984, 0.30 m (1.0 ft) west
of a witness post, and 0.40 m (1.3 ft) above ground level.
BENCH MARK STAMPING: 4409 G 1984
DESIGNATION: 872 4409 G TIDAL
MONUMENTATION: Tidal Station disk VM#: 9583
AGENCY: National Ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: Stainless steel rod OPUS PID:
LATITUDE: 24° 39.5' N ( 24.65830) LONGITUDE: 81° 36.5' W ( -81.60830)
The bench mark is a disk located 15.54 m (51.0 ft) SW of Reference Mark DUG RM 1
1934, 7 m (24 ft) SE of the outer edge of the mangroves, 1.13 m (3.7 ft) WSW of
the center of the broken concrete monument for former Triangulation Station DUG
1934, and 0.30 m (1.0 ft) west of a witness post. The bench mark is 0.03 m (0.1
ft) above ground level, crimped to the top of a stainless steel rod driven 8 m
(26 ft), and encased in a 6-inch PVC pipe projecting 0.09 m (0.3 ft) above
ground level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 5
Station ID: 8724409 PUBLICATION DATE: 11/13/2003
Name: INNER NARROWS
FL
NOAA Chart: 11445 Latitude: 24° 39.5' N ( 24.65830)
USGS Quad: SUGARLOAF KEY Longitude: 81° 36.5' W ( -81.60830)
T I D A L D A T U M S
Tidal datums at INNER NARROWS based on:
LENGTH OF SERIES: 2 MONTHS
TIME PERIOD: September 1974 - October 1974
TIDAL EPOCH: 1983-2001
CONTROL TIDE STATION: 8724580 KEY WEST
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
MEAN HIGHER HIGH WATER MHHW = 0.664
MEAN HIGH WATER MHW = 0.591
MEAN TIDE LEVEL MTL = 0.327
MEAN SEA LEVEL MSL = 0.296
MEAN LOW WATER MLW = 0.062
MEAN LOWER LOW WATER MLLW = 0.000
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
DUG RM 1 1934 1.039 0.448
NO 4 1974 0.694 0.103
NO 5 1974 0.807 0.216
4409 F 1984 1.081 0.490
4409 G 1984 0.774 0.183
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
Station ID: 8724409 PUBLICATION DATE: 11/13/2003
Name: INNER NARROWS
FL
NOAA Chart: 11445 Latitude: 24° 39.5' N ( 24.65830)
USGS Quad: SUGARLOAF KEY Longitude: 81° 36.5' W ( -81.60830)
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.