Published Bench Mark Sheet for 9450970 ENTRANCE TO ZIMOVIA STRAIT ALASKA
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 5
PUBLICATION DATE: 08/10/2001
Station ID: 9450970 SUPERCEDED DATE: 04/21/2003
Name: ENTRANCE TO ZIMOVIA STRAIT
ALASKA
NOAA Chart: 17385 Latitude: 56° 7.1' N
USGS Quad: PETERSBURG (A-1) Longitude: 132° 4.7' W
To reach the tidal marks from Wrangell via boat, proceed 26.3 km (14.3 nm) south
from Wrangell Harbor through Zimovia Strait until abeam of Anita Point. Then
proceed 21.5 km (11.7 nm) SE through Zimovia Strait until abeam of Thoms Point
located north of the north tip of Frost Island, on the southernmost tip of
Wrangell Island. Then proceed 1.1 km (0.6 nm) NW of the southernmost extent of
Wrangell Island. The bench marks, staff, and tide gauge were located on the
beach in the vicinity.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 0970 E 2001
DESIGNATION: 945 0970 E
MONUMENTATION: Tidal Station disk VM#: 16490
AGENCY: National Ocean Service (NOS) PID:
SETTING CLASSIFICATION: Rock outcrop
The primary bench mark is a disk set flush in a bedrock outcrop, 31 m (102 ft)
NNW of the seaward most extent of the point of land just west of the
southern-most extent of Thoms Point, 20.51 m (67.3 ft) SE of a clearing that
extends from the west to the south shore of the point, 14.50 m (47.6 ft) NW (345
degrees magnetic) from bench mark 0970 D 2001, 12.30 m (40.4 ft) east of the
vegetation line, and 6.50 m (21.3 ft) north of a 3 m x 3 m (10 ft x 10 ft)
triangular granite rock.
BENCH MARK STAMPING: 0970 A 2001
DESIGNATION: 945 0970 A
MONUMENTATION: Tidal Station disk VM#: 16486
AGENCY: National Ocean Service (NOS) PID:
SETTING CLASSIFICATION: Rock outcrop
The bench mark is a disk set flush in a black bedrock outcrop with intrusions of
quartz, located on Thoms Point, approximately 355 m (1,164 ft) NW from the
southern-most tip of Wrangell Island, NW (319 degrees magnetic) of the west
extent of Found Island, and WNW (293 degrees magnetic) of the east extent of
Found Island, 15.60 m (51.2 ft) WNW (293 degrees magnetic) from bench mark 0970
B 2001, and 8 m (26 ft) seaward of the vegetation line.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 5
PUBLICATION DATE: 08/10/2001
Station ID: 9450970 SUPERCEDED DATE: 04/21/2003
Name: ENTRANCE TO ZIMOVIA STRAIT
ALASKA
NOAA Chart: 17385 Latitude: 56° 7.1' N
USGS Quad: PETERSBURG (A-1) Longitude: 132° 4.7' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 0970 B 2001
DESIGNATION: 945 0970 B
MONUMENTATION: Tidal Station disk VM#: 16487
AGENCY: National Ocean Service (NOS) PID:
SETTING CLASSIFICATION: Rock outcrop
The bench mark is a disk set flush in a black bedrock located on the SW extent
of Thoms Point, approximately 350 m (1,148 ft) NW (264 degrees magnetic) of the
southern-most extent of Thoms Point, SE (140 degrees magnetic) from a day
marker located on the west side of Found Island, ESE (113 degrees magnetic) from
the east extent of Found Island, 15.6 m (51.2 ft) ESE (113 degrees magnetic)
from bench mark 0970 A 2001, 10 m (33 ft) seaward from the vegetation line, and
4 m (13 ft) shoreward of the apparent high water line.
BENCH MARK STAMPING: 0970 C 2001
DESIGNATION: 945 0970 C
MONUMENTATION: Tidal Station disk VM#: 16488
AGENCY: National Ocean Service (NOS) PID:
SETTING CLASSIFICATION: Rock outcrop
The bench mark is a disk set flush in a bedrock outcrop located on the SW extent
of Thoms Point, approximately 330 m (1,083 ft) NW (264 degrees magnetic) of the
southern-most extent of Thoms Point, 19 m (64 ft) seaward of the vegetation
line, 13.01 m (42.7 ft) ESE (109 magnetic) of bench mark 0970 A 2001, and 13.01
m (42.7 ft) south (175 degrees magnetic) from bench mark 0970 D 2001.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
PUBLICATION DATE: 08/10/2001
Station ID: 9450970 SUPERCEDED DATE: 04/21/2003
Name: ENTRANCE TO ZIMOVIA STRAIT
ALASKA
NOAA Chart: 17385 Latitude: 56° 7.1' N
USGS Quad: PETERSBURG (A-1) Longitude: 132° 4.7' W
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 0970 D 2001
DESIGNATION: 945 0970 D
MONUMENTATION: Tidal Station disk VM#: 16489
AGENCY: National Ocean Service (NOS) PID:
SETTING CLASSIFICATION: Rock outcrop
The bench mark is a disk set flush in a bedrock outcrop, located approximately
325 m (1,066 ft) WNW (268 degrees magnetic) of the southern-most extent of
Thoms Point, 14.51 m (47.6 ft) SSW (165 degrees magnetic) from bench mark 0970 E
2001, 13.01 m (42.7 ft) north (355 degrees magnetic) of bench mark 0970 C 2001,
and 11.50 m (37.7 ft) seaward of the vegetation line.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 5
PUBLICATION DATE: 08/10/2001
Station ID: 9450970 SUPERCEDED DATE: 04/21/2003
Name: ENTRANCE TO ZIMOVIA STRAIT
ALASKA
NOAA Chart: 17385 Latitude: 56° 7.1' N
USGS Quad: PETERSBURG (A-1) Longitude: 132° 4.7' W
T I D A L D A T U M S
Tidal datums at ENTRANCE TO ZIMOVIA STRAIT based on:
LENGTH OF SERIES: 69 HWS AND 70 LWS
TIME PERIOD: April 6, 2001 - May 12, 2001
TIDAL EPOCH: 1960-1978
CONTROL TIDE STATION: 9450460 KETCHIKAN, TONGASS NARROWS
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
MEAN HIGHER HIGH WATER (MHHW) = 4.962
MEAN HIGH WATER (MHW) = 4.698
MEAN TIDE LEVEL (MTL) = 2.584
MEAN SEA LEVEL (MSL) = 2.583
MEAN LOW WATER (MLW) = 0.470
MEAN LOWER LOW WATER (MLLW) = 0.000
National Geodetic Vertical Datum (NGVD 29)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
0970 E 2001 5.380 0.682
0970 A 2001 4.553 -0.145
0970 B 2001 5.394 0.696
0970 C 2001 4.319 -0.379
0970 D 2001 5.530 0.832
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
PUBLICATION DATE: 08/10/2001
Station ID: 9450970 SUPERCEDED DATE: 04/21/2003
Name: ENTRANCE TO ZIMOVIA STRAIT
ALASKA
NOAA Chart: 17385 Latitude: 56° 7.1' N
USGS Quad: PETERSBURG (A-1) Longitude: 132° 4.7' 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 (NAVD 88).
NGVD 29 is a fixed datum adopted as a national standard geodetic reference for
heights but is now considered superseded. NGVD 29 is sometimes referred to as
Sea Level Datum of 1929 or as Mean Sea Level on some early issues of Geological
Survey Topographic Quads. NGVD 29 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 NGVD 29 are available from the National
Geodetic Survey (NGS) data base via the World Wide Web at
National Geodetic Survey.
NAVD 88 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. NAVD 88 replaces NGVD 29 as the national
standard geodetic reference for heights. Bench mark elevations relative to
NAVD 88 are available from NGS through the World Wide Web at
National Geodetic Survey.
NGVD 29 and NAVD 88 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 NAVD 88 elevation is shown on the Elevations of Tidal Datums Table Referred
to MLLW only when two or more of the bench marks listed have NAVD 88 elevations.
The NAVD 88 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, NAVD 88 bench mark elevations computed indirectly from the tidal
datums elevation table may differ slightly from NAVD 88 elevations listed for
each bench mark in the NGS database.
|