U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 4
PUBLICATION DATE: 03/24/1983
Station ID: 8634437 SUPERCEDED DATE: 04/21/2003
Name: MOUNT VERNON, POTOMAC RIVER
VIRGINIA
NOAA Chart: 12289 Latitude: 38° 42.3' N
USGS Quad: MOUNT VERNON Longitude: 77° 5.3' W
To reach the tidal bench marks proceed south along Mt. Vernon Memorial Highway
from Alexandria, Virginia, and over Little Hunting Creek to Mt. Vernon. The
tide gage and staff were located on the pier at Mt. Vernon.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: MV NO 1 1974
MONUMENTATION: Survey Disk VM#: 3405
AGENCY: PID:
SETTING CLASSIFICATION: Concrete
The bench mark is 352 feet (107 m) south of Bench Mark MV NO 2 1974, 132 feet
(40 m) north of north edge of the boat pier, and 1.2 feet (0.4 m) from the
inside edge of stone wall.
BENCH MARK STAMPING: MV NO 2 1974
MONUMENTATION: Survey Disk VM#: 3406
AGENCY: PID:
SETTING CLASSIFICATION: Concrete
The bench mark is 48.4 feet (14.8 m) north of boat pier, 12.0 feet (3.7 m) from
inside edge of a stone seawall, and 5.0 feet (1.5 m) north of first wooden rail
fence from the boat pier.
BENCH MARK STAMPING: MV NO 3 1974
MONUMENTATION: Survey Disk VM#: 3407
AGENCY: PID:
SETTING CLASSIFICATION: Concrete
The bench mark is 220 feet (67 m) south of second wooden rail fence north of the
boat pier and 2.0 feet (0.6 m) from the inside edge of the stone seawall.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 4
PUBLICATION DATE: 03/24/1983
Station ID: 8634437 SUPERCEDED DATE: 04/21/2003
Name: MOUNT VERNON, POTOMAC RIVER
VIRGINIA
NOAA Chart: 12289 Latitude: 38° 42.3' N
USGS Quad: MOUNT VERNON Longitude: 77° 5.3' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: VERNON NO 2 1928 1940
MONUMENTATION: Survey Disk VM#: 3408
AGENCY: PID#: HV2386
SETTING CLASSIFICATION: Concrete
The bench mark is 58.8 feet (17.9 m) west of Bench Mark Vernon 1928, 35.0 feet
(10.7 m) north of wooden fence and on SW corner of a dirt road.
BENCH MARK STAMPING: VERNON 1928
MONUMENTATION: Triangulation Disk VM#: 3409
AGENCY: PID#: HV2385
SETTING CLASSIFICATION: Concrete
The bench mark is 10.0 feet (3.0 m) north of wooden rail fence (second wood rail
fence from the boat pier) and north of boat pier.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 4
PUBLICATION DATE: 03/24/1983
Station ID: 8634437 SUPERCEDED DATE: 04/21/2003
Name: MOUNT VERNON, POTOMAC RIVER
VIRGINIA
NOAA Chart: 12289 Latitude: 38° 42.3' N
USGS Quad: MOUNT VERNON Longitude: 77° 5.3' W
T I D A L D A T U M S
Tidal datums at MOUNT VERNON, POTOMAC RIVER based on:
LENGTH OF SERIES: 1 MONTH
TIME PERIOD: OCTOBER 1974
TIDAL EPOCH: 1960-1978
CONTROL TIDE STATION: 8594900 WASHINGTON, DC
Elevations of tidal datums referred to Mean Low Water (MLW), in FEET:
HIGHEST OBSERVED WATER LEVEL (11/24/1974) = 3.60
MEAN HIGH WATER MHW = 2.10
MEAN TIDE LEVEL MTL = 1.05
MEAN LOW WATER MLW = 0.00
LOWEST OBSERVED WATER LEVEL (10/03/1974) = -1.50
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In FEET above:
Stamping or Designation MLW MHW
MV NO 1 1974 5.48 3.38
MV NO 2 1974 5.32 3.22
MV NO 3 1974 5.32 3.22
VERNON NO 2 1928 1940 8.21 6.11
VERNON 1928 5.84 3.74
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 4
PUBLICATION DATE: 03/24/1983
Station ID: 8634437 SUPERCEDED DATE: 04/21/2003
Name: MOUNT VERNON, POTOMAC RIVER
VIRGINIA
NOAA Chart: 12289 Latitude: 38° 42.3' N
USGS Quad: MOUNT VERNON Longitude: 77° 5.3' 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.