U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 4
PUBLICATION DATE: 06/11/1987
Station ID: 8724448 SUPERCEDED DATE: 04/21/2003
Name: WALTZ KEY, WALTZ KEY BASIN
FLORIDA
NOAA Chart: 11445 Latitude: 24° 38.8' N
USGS Quad: SNIPE KEYS Longitude: 81° 39.2' W
To reach the tidal bench marks from the west end of the bridge between Big
Coppitt Key and Saddlebunch Keys, proceed by boat NW for 1.7 statute miles (2.7
km) and then north for 1.8 statute miles (2.9 km) to Waltz Key. The bench marks
are located in the middle of the key. The tide gage and staff were located on
the west side of the key.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: WALL KEY 2 NO 1 1934
MONUMENTATION: Survey Disk VM#: 9618
AGENCY: PID#: AE4419
SETTING CLASSIFICATION: Concrete Monument
The bench mark is set in a concrete monument on a pile, about 295 feet (90 m)
north of the southern tip of the key, 42.4 feet (12.9 m) SSE of Bench Mark WALL
KEY 2 1934, 1.4 feet (0.4 m) north of a witness post, and 1 foot (0.3 m) above
the ground.
BENCH MARK STAMPING: WALL KEY 2 1934
MONUMENTATION: Survey Disk VM#: 9617
AGENCY: PID#: AA1118
SETTING CLASSIFICATION: Concrete Monument
The bench mark is set in a concrete monument on a pile, about 311 feet (95 m)
north of the south end of the key, 81 feet (25 m) west of a witness sign nailed
to a tree at the waters edge, 5.6 feet (1.7 m) SSE of an old witness sign nailed
to a tree, 0.5 foot (0.2 m) east of a new witness post, and 1 foot (0.3 m) above
the ground.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 4
PUBLICATION DATE: 06/11/1987
Station ID: 8724448 SUPERCEDED DATE: 04/21/2003
Name: WALTZ KEY, WALTZ KEY BASIN
FLORIDA
NOAA Chart: 11445 Latitude: 24° 38.8' N
USGS Quad: SNIPE KEYS Longitude: 81° 39.2' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: WALL KEY 2 NO 2 1934
MONUMENTATION: Survey Disk VM#: 9619
AGENCY: PID#: AE4420
SETTING CLASSIFICATION: Concrete Monument
The bench mark is set in a concrete monument on a pile, about 330 feet (100 m)
north of the southern tip of the key, 76.0 feet (23.2 m) NNW of Bench Mark WALL
KEY 2 NO 1 1934, 53.0 feet (16.2 m) NW of Bench Mark WALL KEY 2 1934, 0.6 foot
(0.2 m) east of a witness post, and 1 foot (0.3 m) above the ground.
BENCH MARK STAMPING: 4448 D 1984
MONUMENTATION: Survey Disk VM#: 9620
AGENCY: PID:
SETTING CLASSIFICATION: Stainless Steel Rod
The bench mark is about 275 feet (84 m) north of the south end of the key, 47.5
feet (14.5 m) SSE of Bench Mark WALL KEY 2 1934, 40.5 feet (12.3 m) SW of Bench
Mark 4448 E 1984, and 1.0 foot (0.3 m) ESE of a witness post. The bench mark is
0.8 foot (0.2 m) above ground, crimped to a stainless steel rod driven 20 feet
(6 m) to refusal, encased in a PVC pipe and concrete kickblock.
BENCH MARK STAMPING: 4448 E 1984
MONUMENTATION: Survey Disk VM#: 9621
AGENCY: PID:
SETTING CLASSIFICATION: Stainless Steel Rod
The bench mark is 45 feet (14 m) ESE of Bench Mark WALL KEY 2 1934, 43 feet (13
m) WSW of a witness sign nailed to a tree at the outer mangrove edge, and 1.2
feet (0.4 m) ESE of a witness post. The bench mark is 0.8 foot (0.2 m) above
ground, crimped to a stainless steel rod driven 20 feet (6 m) to refusal,
encased in a PVC pipe and concrete kickblock.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 4
PUBLICATION DATE: 06/11/1987
Station ID: 8724448 SUPERCEDED DATE: 04/21/2003
Name: WALTZ KEY, WALTZ KEY BASIN
FLORIDA
NOAA Chart: 11445 Latitude: 24° 38.8' N
USGS Quad: SNIPE KEYS Longitude: 81° 39.2' W
T I D A L D A T U M S
Tidal datums at WALTZ KEY, WALTZ KEY BASIN based on:
LENGTH OF SERIES: 1 MONTH
TIME PERIOD: JANUARY 1975
TIDAL EPOCH: 1960-1978
CONTROL TIDE STATION: 8724580 KEY WEST
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in FEET:
HIGHEST OBSERVED WATER LEVEL (01/28/1975) = 2.35
MEAN HIGHER HIGH WATER MHHW = 1.88
MEAN HIGH WATER MHW = 1.59
MEAN TIDE LEVEL MTL = 0.91
MEAN LOW WATER MLW = 0.23
MEAN LOWER LOW WATER MLLW = 0.00
LOWEST OBSERVED WATER LEVEL (12/10/1974) = -1.69
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In FEET above:
Stamping or Designation MLLW MHW
WALL KEY 2 NO 1 1934 2.20 0.61
WALL KEY 2 1934 2.19 0.60
WALL KEY 2 NO 2 1934 2.53 0.94
4448 D 1984 2.45 0.86
4448 E 1984 2.57 0.98
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 4
PUBLICATION DATE: 06/11/1987
Station ID: 8724448 SUPERCEDED DATE: 04/21/2003
Name: WALTZ KEY, WALTZ KEY BASIN
FLORIDA
NOAA Chart: 11445 Latitude: 24° 38.8' N
USGS Quad: SNIPE KEYS Longitude: 81° 39.2' W
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 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.