U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 6
Station ID: 8728261 PUBLICATION DATE: 05/12/2004
Name: ALLIGATOR POINT, SW CAPE
FL
NOAA Chart: 11405 Latitude: 29° 53.7' N ( 29.89500)
USGS Quad: ST. TERESA BEACH Longitude: 84° 23.3' W ( -84.38830)
To reach the tidal bench marks from the intersection of U.S. Highway 98 and
County Road C-370 (Alligator Drive) south of Panacea, proceed SE and west on
County Road C-370 for 20.4 km (12.7 mi) [1.8 km (1.1 mi) beyond a KOA
Campground] to a white frame house on pilings owned by Mr. Kalfas. The bench
marks are along County Road C-370. The tide gage and staff were located on a
pier in the Gulf of Mexico behind the Kalfas house.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 8261 A 1976
DESIGNATION: 872 8261 A TIDAL FLDNR
MONUMENTATION: Tidal Station disk VM#: 9783
AGENCY: Florida Department of Natural Resources
(FLDNR) IDB PID#: AS0464
SETTING CLASSIFICATION: Concrete monument OPUS PID:
LATITUDE: 29° 53.7' N ( 29.89500) LONGITUDE: 84° 22.2' W ( -84.37000)
The primary bench mark is a disk set in the top of a concrete monument, 1.0 km
(0.6 mi) east of bench mark 8261 G 1977, 48.77 m (160.0 ft) east of the entrance
to the campground, 10.61 m (34.8 ft) north of the centerline of the highway,
5.97 m (19.6 ft) WSW of telephone cable box #63, 2.90 m (9.5 ft) south of the SE
corner of the campground fence, 0.3 m (1 ft) south of a witness post, and at
ground level. NOTE: Mark not found in 1998 by US Power Squadron.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 6
Station ID: 8728261 PUBLICATION DATE: 05/12/2004
Name: ALLIGATOR POINT, SW CAPE
FL
NOAA Chart: 11405 Latitude: 29° 53.7' N ( 29.89500)
USGS Quad: ST. TERESA BEACH Longitude: 84° 23.3' W ( -84.38830)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 8261 B 1976
DESIGNATION: 872 8261 B TIDAL FLDNR
MONUMENTATION: Tidal Station disk VM#: 9784
AGENCY: Florida Department of Natural Resources
(FLDNR) IDB PID#: AS0463
SETTING CLASSIFICATION: Copper-clad steel rod OPUS PID:
LATITUDE: 29° 53.7' N ( 29.89500) LONGITUDE: 84° 23.3' W ( -84.38830)
The bench mark is a disk located at the NW corner of Tom Roberts Road and County
Road C-370 (Alligator Road), 14.08 m (46.2 ft) west of the centerline of Tom
Roberts Road, 10.15 m (33.3 ft) north of the centerline of the highway, 2.93 m
(9.6 ft) SE of a buried cable marker, and 1.83 m (6.0 ft) ENE of a witness post.
The bench mark is crimped to the top of a copper-clad steel rod driven 10.4 m
(34 ft) to refusal, and encased in a PVC pipe and concrete kickblock.
BENCH MARK STAMPING: 8261 C 1976
DESIGNATION: 872 8261 C TIDAL FLDNR
MONUMENTATION: Tidal Station disk VM#: 9785
AGENCY: Florida Department of Natural Resources
(FLDNR) IDB PID#: AS0462
SETTING CLASSIFICATION: Copper-clad steel rod OPUS PID:
LATITUDE: 29° 53.7' N ( 29.89500) LONGITUDE: 84° 22.2' W ( -84.37000)
The bench mark is a disk located on the south side of County Road C-370
(Alligator Drive), 61 m (200 ft) ESE of the intersection of Tom Roberts Road and
County Road C-370, 12.56 m (41.2 ft) south of the centerline of the highway,
9.81 m (32.2 ft) ENE of the NE corner of the Brackett/Spears house, 0.67 m (2.2
ft) north of utility pole #58X742R, and 0.15 m (0.5 ft) north of a witness post.
The bench mark is crimped to to the top of a copper-clad steel rod driven 12.2
m (40 ft) to refusal, and encased in a PVC pipe and concrete kickblock. NOTE:
Mark not found in 1998 by US Power Squadron.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 6
Station ID: 8728261 PUBLICATION DATE: 05/12/2004
Name: ALLIGATOR POINT, SW CAPE
FL
NOAA Chart: 11405 Latitude: 29° 53.7' N ( 29.89500)
USGS Quad: ST. TERESA BEACH Longitude: 84° 23.3' W ( -84.38830)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 8261 D 1976
DESIGNATION: 872 8261 D TIDAL FLDNR
MONUMENTATION: Tidal Station disk VM#: 9786
AGENCY: Florida Department of Natural Resources
(FLDNR) IDB PID#: AS0461
SETTING CLASSIFICATION: Concrete monument OPUS PID:
LATITUDE: 29° 53.7' N ( 29.89500) LONGITUDE: 84° 22.2' W ( -84.37000)
The bench mark is a disk set in the top of a concrete monument, 14.63 m (48.0
ft) ESE of the SE corner of a concrete block cottage east of Tom Roberts Road,
11.28 m (37.0 ft) north of the centerline of County Road C-370, 1.55 m (5.1 ft)
south of powerline pole #5-2060, 0.3 m (1 ft) west of a witness post, and 0.06 m
(0.2 ft) above ground level.
BENCH MARK STAMPING: 8261 E 1976
DESIGNATION: 872 8261 E TIDAL FLDNR
MONUMENTATION: Tidal Station disk VM#: 9787
AGENCY: Florida Department of Natural Resources
(FLDNR) IDB PID#: AS0460
SETTING CLASSIFICATION: Copper-clad steel rod OPUS PID:
LATITUDE: 29° 53.7' N ( 29.89500) LONGITUDE: 84° 23.3' W ( -84.38830)
The bench mark is a disk located 9.66 m (31.7 ft) NNW of the NW corner of a
concrete block house east of Tom Roberts Road, 7.65 m (25.1 ft) NNE of telephone
cable box #59, 7.25 m (23.8 ft) north of utility pole #58X8741, 7.13 m (23.4 ft)
south of the centerline of the highway, 0.3 m (1 ft) north of a witness post.
The bench mark is crimped to the top of a copper-clad steel rod driven 14.6 m
(48.0 ft) to refusal, and encased in a PVC pipe and concrete kickblock. NOTE:
Mark not found in 1998 by US Power Squadron.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 6
Station ID: 8728261 PUBLICATION DATE: 05/12/2004
Name: ALLIGATOR POINT, SW CAPE
FL
NOAA Chart: 11405 Latitude: 29° 53.7' N ( 29.89500)
USGS Quad: ST. TERESA BEACH Longitude: 84° 23.3' W ( -84.38830)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 8261 F 1976
DESIGNATION: 872 8261 F TIDAL FLDNR
MONUMENTATION: Tidal Station disk VM#: 9788
AGENCY: Florida Department of Natural Resources
(FLDNR) IDB PID#: AS0465
SETTING CLASSIFICATION: Copper-clad steel rod OPUS PID:
LATITUDE: 29° 53.7' N ( 29.89500) LONGITUDE: 84° 23.3' W ( -84.38830)
The bench mark is a disk located near the Kalfas' pier, 30.85 m (101.2 ft) NW of
the NW corner of the pier, 28.16 m (92.4 ft) SE of the SE corner piling of the
Kalfas' house, 15.94 m (52.3 ft) WSW of the SW corner of a wood shed, 15.24 m
(50.0 ft) north of the outer edge of the grass line along the beach, and 0.3 m
(1 ft) east of a metal witness post. The bench mark is set 0.46 m (1.5 ft)
below ground level, crimped to the top of a copper-clad steel rod driven 12.2 m
(40 ft) to refusal, and encased in a PVC pipe and concrete kickblock. NOTE:
Mark not found in 1998 by US Power Squadron.
BENCH MARK STAMPING: 8261 G 1977
DESIGNATION: 872 8261 G TIDAL FLDNR
MONUMENTATION: Tidal Station disk VM#: 9789
AGENCY: Florida Department of Natural Resources
(FLDNR) IDB PID#: AS0466
SETTING CLASSIFICATION: Concrete monument OPUS PID:
LATITUDE: 29° 53.7' N ( 29.89500) LONGITUDE: 84° 22.8' W ( -84.38000)
The bench mark is a disk set in the top of a concrete monument, 0.8 km (0.5 mi)
east of bench mark 8261 F 1976, 39.62 m (130.0 ft) south of a water tower, 14.11
m (46.3 ft) east of the centerline of a paved road, 11.52 m (37.8 ft) south of
the centerline of County Road C-370 (Alligator Drive), 8.66 m (28.4 ft) ENE of
powerline pole #58x2396R, 0.61 m (2.0 ft) north of a witness post, and 0.06 m
(0.2 ft) above ground level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 6
Station ID: 8728261 PUBLICATION DATE: 05/12/2004
Name: ALLIGATOR POINT, SW CAPE
FL
NOAA Chart: 11405 Latitude: 29° 53.7' N ( 29.89500)
USGS Quad: ST. TERESA BEACH Longitude: 84° 23.3' W ( -84.38830)
T I D A L D A T U M S
Tidal datums at ALLIGATOR POINT, SW CAPE based on:
LENGTH OF SERIES: 6 MONTHS
TIME PERIOD: February 1977 - July 1977
TIDAL EPOCH: 1983-2001
CONTROL TIDE STATION: 8727520 CEDAR KEY, GULF OF MEXICO
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
MEAN HIGHER HIGH WATER MHHW = 0.846
MEAN HIGH WATER MHW = 0.779
MEAN TIDE LEVEL MTL = 0.479
North American Vertical Datum NAVD88 = 0.457
MEAN SEA LEVEL MSL = 0.454
MEAN LOW WATER MLW = 0.178
MEAN LOWER LOW WATER MLLW = 0.000
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
8261 A 1976 2.702 1.923
8261 B 1976 2.914 2.135
8261 C 1976 3.477 2.698
8261 D 1976 2.800 2.021
8261 E 1976 3.137 2.358
8261 F 1976 2.624 1.845
8261 G 1977 3.615 2.836
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 6 of 6
Station ID: 8728261 PUBLICATION DATE: 05/12/2004
Name: ALLIGATOR POINT, SW CAPE
FL
NOAA Chart: 11405 Latitude: 29° 53.7' N ( 29.89500)
USGS Quad: ST. TERESA BEACH Longitude: 84° 23.3' W ( -84.38830)
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.