Superseded Bench Mark Sheet for 9452421, CHILKAT INLET AK

Present Epoch

Printable version

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
Datums Page                                                        Page  1 of  5

                                                   PUBLICATION DATE:  09/11/2000
Station ID: 9452421                                SUPERCEDED DATE:   04/21/2003
Name:       CHILKAT INLET                                     
            ALASKA
NOAA Chart: 16700                                  Latitude:         59° 10.2' N
USGS Quad:  SKAGWAY (A-2)                          Longitude:       135° 24.0' W


To reach the tidal bench marks, proceed to the eastern bank of Chilkat Inlet,
approximately 400 m (1312 ft) south of Letnikof Cove Light F1 R 4 sec.  The
bench marks are located in the vicinity on the SE to south side. The tide gauge
was placed on a small wooden platform, behind a rock cluster, 40 m inland from
the water's edge, approximately 6 m above apparent high water. 


                         T I D A L   B E N C H   M A R K S


                 PRIMARY BENCH MARK STAMPING:  2421 C 1998
                         DESIGNATION:          945 2421 C

MONUMENTATION:           Tidal Station disk                        VM#:    14041
AGENCY:                  National Ocean Service (NOS)              PID:         
SETTING CLASSIFICATION:  Rock outcrop


The primary bench mark is a disk set on top of one of the highest points of a
prominent dark-coloured, steep-faced, mussel-encrusted, rocky ledge,
sharp-featured rock, on the eastern bank of Chilkat Inlet, approximately 320 m
(1050 ft) south of Letnikof Cove Light F1 R 4 sec, located approximately 10 m
(33 ft) inland of the water's edge, 66 m (216 ft) NW (290 degrees magnetic) from
bench mark 2421 B 1998, and approximately 2.50 m (8.2 ft) above the apparent
high water line.



                         BENCH MARK STAMPING:  2421 A 1998
                         DESIGNATION:          945 2421 A

MONUMENTATION:           Tidal Station disk                        VM#:    14039
AGENCY:                  National Ocean Service (NOS)              PID:         
SETTING CLASSIFICATION:  Rock outcrop


The bench mark is a disk set on top of a distinctive, flat, light-coloured, 1m x
1 m x 1 m (4 ft x 3 ft x 2 ft) rock on the eastern bank of Chilkat Inlet,
approximately 400 m (1312 ft) south of Letnikof Cove Light F1 R 4 sec, along a
relatively flat section shore heavily strewn with small boulders and drift wood
and sparsely covered with tall grass, approximately 100 m (308 ft) north of an
isolated waterfront house, 39 m (128 ft) SE (60 degrees magnetic) from bench
mark 2421 B 1998, 30 m (98 ft) inland from the waterline, and 2 m (7 ft) away
from the treeline.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  2 of  5

                                                   PUBLICATION DATE:  09/11/2000
Station ID: 9452421                                SUPERCEDED DATE:   04/21/2003
Name:       CHILKAT INLET                                     
            ALASKA
NOAA Chart: 16700                                  Latitude:         59° 10.2' N
USGS Quad:  SKAGWAY (A-2)                          Longitude:       135° 24.0' W


                         T I D A L   B E N C H   M A R K S


                         BENCH MARK STAMPING:  2421 B 1998
                         DESIGNATION:          945 2421 B

MONUMENTATION:           Tidal Station disk                        VM#:    14040
AGENCY:                  National Ocean Service (NOS)              PID:         
SETTING CLASSIFICATION:  Rock outcrop


The bench mark is a disk set on top of a distinctive, flat, light-coloured, 1m x
1 m x 1 m (4 ft x 3 ft x 2 ft) rock on the eastern bank of Chilkat Inlet,
approximately 400 m (1312 ft) south of Letnikof Cove Light F1 R 4 sec, along a
relatively flat section shore heavily strewn with small boulders and drift wood
and sparsely covered with tall grass, approximately 100 m (308 ft) north of an
isolated waterfront house, 39 m (128 ft) NW (300 degrees magnetic) from bench
mark 2421 A 1998, 30 m (98 ft) inland from the waterline, and 2 m (7 ft) away
from the treeline.



                         BENCH MARK STAMPING:  2421 D 1998
                         DESIGNATION:          945 2421 D

MONUMENTATION:           Tidal Station disk                        VM#:    14042
AGENCY:                  National Ocean Service (NOS)              PID:         
SETTING CLASSIFICATION:  Rock outcrop


The bench mark is a disk set on top of a low-lying flat 1 m x 1 m x 0.3 m (2 ft
x 3 ft x 1 ft) rock located on the eastern bank of Chilkat Inlet, approximately
290 m (951 ft) SSE of Letnikof Cove Light F1 R 4 sec, on a boulder strewn
section of beach just north of the prominent, dark-coloured, steep-faced,
mussel-encrusted rocky ledge, 65 m (213 ft) NE (010 degrees magnetic) from bench
mark 2421 C 1998, and 8 m (26 ft) inland of the apparent high water line.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  3 of  5

                                                   PUBLICATION DATE:  09/11/2000
Station ID: 9452421                                SUPERCEDED DATE:   04/21/2003
Name:       CHILKAT INLET                                     
            ALASKA
NOAA Chart: 16700                                  Latitude:         59° 10.2' N
USGS Quad:  SKAGWAY (A-2)                          Longitude:       135° 24.0' W


                         T I D A L   B E N C H   M A R K S


                         BENCH MARK STAMPING:  2421 E 1998
                         DESIGNATION:          945 2421 E

MONUMENTATION:           Tidal Station disk                        VM#:    14043
AGENCY:                  National Ocean Service (NOS)              PID:         
SETTING CLASSIFICATION:  Rock outcrop


The bench mark is a disk set on top of a low-lying flat 1 m x 1 m x 0.3 m (2 ft
x 3 ft x 1 ft) rock located on the eastern bank of Chilkat Inlet, approximately
235 m (771 ft) SE of Letnikof Cove Light F1 R 4 sec, on a boulder strewn section
of beach just north of the prominent, dark-coloured, steep-faced,
mussel-encrusted rocky ledge,  56 m (184 ft) NW (340 degrees magnetic) from
bench mark 2421 D 1998, 15 m (49 ft) inland of the apparent high water line, and
10 m (33 ft) below the treeline.

                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  4 of  5

                                                   PUBLICATION DATE:  09/11/2000
Station ID: 9452421                                SUPERCEDED DATE:   04/21/2003
Name:       CHILKAT INLET                                     
            ALASKA
NOAA Chart: 16700                                  Latitude:         59° 10.2' N
USGS Quad:  SKAGWAY (A-2)                          Longitude:       135° 24.0' W


                            T I D A L   D A T U M S 


Tidal datums at CHILKAT INLET based on:

     LENGTH OF SERIES:      81 HW and 80 LW
     TIME PERIOD:           MAY 11 - JUNE 21, 1998
     TIDAL EPOCH:           1960-1978
     CONTROL TIDE STATION:  9452400 SKAGWAY, TAIYA INLET


Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:

     MEAN HIGHER HIGH WATER                     MHHW   =  5.020
     MEAN HIGH WATER                            MHW    =  4.722
     MEAN SEA LEVEL                             MSL    =  2.633
     MEAN TIDE LEVEL                            MTL    =  2.600
     MEAN LOW WATER                             MLW    =  0.477
     MEAN LOWER LOW WATER                       MLLW   =  0.000



Bench Mark Elevation Information                In METERS above:

     Stamping or Designation                    MLLW        MHW

     2421 C 1998                                 5.954    1.232
     2421 A 1998                                 6.842    2.120
     2421 B 1998                                 7.265    2.543
     2421 D 1998                                 5.833    1.111
     2421 E 1998                                 6.808    2.086


                          U.S. DEPARTMENT OF COMMERCE
                National Oceanic and Atmospheric Administration
                            National Ocean Service
                                                                   Page  5 of  5

                                                   PUBLICATION DATE:  09/11/2000
Station ID: 9452421                                SUPERCEDED DATE:   04/21/2003
Name:       CHILKAT INLET                                     
            ALASKA
NOAA Chart: 16700                                  Latitude:         59° 10.2' N
USGS Quad:  SKAGWAY (A-2)                          Longitude:       135° 24.0' 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.

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