U.S. DEPARTMENT OF COMMERCE
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National Ocean Service
Datums Page Page 1 of 6
Station ID: 8724199 PUBLICATION DATE: 05/28/2004
Name: CRAWL KEY, BIG SPANISH CHANNEL
FL
NOAA Chart: 11445 Latitude: 24° 45.4' N ( 24.75670)
USGS Quad: HORSESHOE KEYS Longitude: 81° 21.5' W ( -81.35830)
To reach the tidal bench marks from Bogie Channel Bridge linking Big Pine Key to
No Name Key, proceed by boat NNW for 6.6 km (4.1 statute mi) to the NE point of
Crawl Key. The bench marks are located in a clearing on the NE point of Crawl
Key. The tide gage and staff were located offshore, NE of the NE tip of the
key.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: CRAWL KEY RM 1 1934-35
DESIGNATION: CRAWL KEY RM 1
MONUMENTATION: Reference Mark disk VM#: 6427
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#: AE4397
SETTING CLASSIFICATION: Concrete monument OPUS PID:
LATITUDE: 24° 45.4' N ( 24.75670) LONGITUDE: 81° 21.5' W ( -81.35830)
The bench mark is a disk set flush in a 0.21 m (0.7 ft) square concrete
monument, 19.35 m (63.5 ft) WNW of bench mark CRAWL KEY 1934-35, 0.3 m (1 ft)
east of a witness post, and 0.24 m (0.8 ft) above ground level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 6
Station ID: 8724199 PUBLICATION DATE: 05/28/2004
Name: CRAWL KEY, BIG SPANISH CHANNEL
FL
NOAA Chart: 11445 Latitude: 24° 45.4' N ( 24.75670)
USGS Quad: HORSESHOE KEYS Longitude: 81° 21.5' W ( -81.35830)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: CRAWL KEY 1934-35
DESIGNATION: CRAWL KEY
MONUMENTATION: Triangulation Station disk VM#: 6426
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#: AA1569
SETTING CLASSIFICATION: Concrete monument OPUS PID:
LATITUDE: 24° 45.4' N ( 24.75670) LONGITUDE: 81° 21.5' W ( -81.35830)
The primary bench mark is a disk set flush in a 0.21 m (0.7 ft) square concrete
monument, 70 m (230 ft) south of the outer edge of mangroves on the north, 35 m
(115 ft) west of the outer edge of the mangroves on the east, 28.90 m (94.8 ft)
SSW of bench mark CRAWL KEY RM 2 1934-35, 0.37 m (1.2 ft) NW of a witness post,
and 0.24 m (0.8 ft) above ground level.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 6
Station ID: 8724199 PUBLICATION DATE: 05/28/2004
Name: CRAWL KEY, BIG SPANISH CHANNEL
FL
NOAA Chart: 11445 Latitude: 24° 45.4' N ( 24.75670)
USGS Quad: HORSESHOE KEYS Longitude: 81° 21.5' W ( -81.35830)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: CRAWL KEY RM 2 1934-35
DESIGNATION: CRAWL KEY RM 2
MONUMENTATION: Reference Mark disk VM#: 6428
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#: AE4398
SETTING CLASSIFICATION: Concrete monument OPUS PID:
LATITUDE: 24° 45.4' N ( 24.75670) LONGITUDE: 81° 21.5' W ( -81.35830)
The bench mark is a disk set flush in a 0.21 m (0.7 ft) square concrete
monument, 34.23 m (112.3 ft) NE of bench mark CRAWL KEY RM NO 1 1934-35, 16.34 m
(53.6 ft) SSW of bench mark NO 3 1974, 0.21 m (0.7 ft) SW of a witness post, and
0.24 m (0.8 ft) above ground level.
BENCH MARK STAMPING: NO 3 1974
DESIGNATION: 872 4199 TIDAL 3
MONUMENTATION: Tidal Station disk VM#: 6429
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Copper-clad steel rod OPUS PID:
LATITUDE: 24° 45.4' N ( 24.75670) LONGITUDE: 81° 21.5' W ( -81.35830)
The bench mark is a disk located near the NE end of the clearing, 46 m (151 ft)
NNE of bench mark CRAWL KEY RM 1 1934-35, and 5 m (15 ft) west of the mangroves
on the eastern shore. The bench mark is set 12 cm (0.4 ft) above ground level,
crimped to the top of a copper-clad steel rod driven an unspecified depth to
refusal and encased in concrete.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 6
Station ID: 8724199 PUBLICATION DATE: 05/28/2004
Name: CRAWL KEY, BIG SPANISH CHANNEL
FL
NOAA Chart: 11445 Latitude: 24° 45.4' N ( 24.75670)
USGS Quad: HORSESHOE KEYS Longitude: 81° 21.5' W ( -81.35830)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: NO 5 1974
DESIGNATION: 872 4199 TIDAL 5
MONUMENTATION: Tidal Station disk VM#: 6430
AGENCY: National Ocean Survey (NOS) IDB PID#:
SETTING CLASSIFICATION: Copper-clad steel rod OPUS PID:
LATITUDE: 24° 45.4' N ( 24.75670) LONGITUDE: 81° 21.5' W ( -81.35830)
The bench mark is a disk located 26 m (85 ft) SSW of the outer edge of
mangroves, 20.24 m (66.4 ft) NNE of bench mark NO 3 1974, 4.27 m (14.0 ft) SSW
of a witness sign nailed to a tree, and 0.27 m (0.9 ft) SE of a witness post.
The bench mark is set 0.12 m (0.4 ft) above ground level, crimped to the top of
a copper-clad steel rod driven an unspecified depth to refusal, and encased in
concrete.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 6
Station ID: 8724199 PUBLICATION DATE: 05/28/2004
Name: CRAWL KEY, BIG SPANISH CHANNEL
FL
NOAA Chart: 11445 Latitude: 24° 45.4' N ( 24.75670)
USGS Quad: HORSESHOE KEYS Longitude: 81° 21.5' W ( -81.35830)
T I D A L D A T U M S
Tidal datums at CRAWL KEY, BIG SPANISH CHANNEL based on:
LENGTH OF SERIES: 1 MONTH
TIME PERIOD: August 1974 - August 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 = 0.680
MEAN HIGH WATER MHW = 0.613
MEAN TIDE LEVEL MTL = 0.354
MEAN SEA LEVEL MSL = 0.328
MEAN LOW WATER MLW = 0.095
MEAN LOWER LOW WATER MLLW = 0.000
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
CRAWL KEY RM 1 1934-35 1.077 0.464
CRAWL KEY 1934-35 0.928 0.315
CRAWL KEY RM 2 1934-35 0.939 0.326
NO 3 1974 0.866 0.253
NO 5 1974 0.909 0.296
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 6 of 6
Station ID: 8724199 PUBLICATION DATE: 05/28/2004
Name: CRAWL KEY, BIG SPANISH CHANNEL
FL
NOAA Chart: 11445 Latitude: 24° 45.4' N ( 24.75670)
USGS Quad: HORSESHOE KEYS Longitude: 81° 21.5' W ( -81.35830)
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.