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Datums Page Page 1 of 5
Station ID: 9450544 PUBLICATION DATE: 09/05/2003
Name: HOLLIS ANCHORAGE, KASAAN BAY
AK
NOAA Chart: 17426 Latitude: 55° 28.8' N ( 55.48000)
USGS Quad: CRAIG (B-2) Longitude: 132° 38.7' W (-132.64500)
To reach the tidal bench marks from Ketchikan, Alaska, navigate 72 km (39 nm)
WNW towards Hollis, Alaska. Then proceed 0.6 km (0.3 nm) SE of the Hollis City
Dock along the east-west rock shoreline on the northern shore of a small
protected bight. The bench marks are located along the shore. The tide gauge
was located on the beach.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 3
DESIGNATION: 945 0544 TIDAL 3
MONUMENTATION: Tidal Station disk VM#: 16713
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#:
SETTING CLASSIFICATION: Rock ledge OPUS PID:
LATITUDE: 55° 28.8' N ( 55.48000) LONGITUDE: 132° 38.7' W (-132.64500)
The bench mark is a disk, set in ragged rocky ledge about 6 m (20 ft) wide,
about 11 m (36 ft) west from bench mark 1, about 12 m (38 ft) west from bench
mark 2, flat-topped peak appears about one-fourth way from south point entrance
to Hollis to islet on north side of entrance.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 5
Station ID: 9450544 PUBLICATION DATE: 09/05/2003
Name: HOLLIS ANCHORAGE, KASAAN BAY
AK
NOAA Chart: 17426 Latitude: 55° 28.8' N ( 55.48000)
USGS Quad: CRAIG (B-2) Longitude: 132° 38.7' W (-132.64500)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 2
DESIGNATION: 945 0544 TIDAL 2
MONUMENTATION: Tidal Station disk VM#: 16712
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#:
SETTING CLASSIFICATION: Rock ledge OPUS PID:
LATITUDE: 55° 28.8' N ( 55.48000) LONGITUDE: 132° 38.7' W (-132.64500)
The bench mark is a disk set in crevice of outcropping ledge, in about center of
ledge and under overhanging trees, on northeast shore of channel leading into
Hollis Anchorage, north-northeast of Althouse Point, almost due north of small
wooded islet on eastern side of entrance into Hollis Anchorage, and about 75
degrees (true) from shoal baring at half tide on eastern side of Hollis
Anchorage.
BENCH MARK STAMPING: NO 4 1953
DESIGNATION: 945 0544 TIDAL 4
MONUMENTATION: Tidal Station disk VM#: 16714
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#:
SETTING CLASSIFICATION: Rock ledge OPUS PID:
LATITUDE: 55° 28.8' N ( 55.48000) LONGITUDE: 132° 38.7' W (-132.64500)
The bench mark is a disk set in flat-topped rock about 1 m (3 ft) square shape,
5 m (15 ft) WNW of bench mark 3 and under overhanging trees.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 5
Station ID: 9450544 PUBLICATION DATE: 09/05/2003
Name: HOLLIS ANCHORAGE, KASAAN BAY
AK
NOAA Chart: 17426 Latitude: 55° 28.8' N ( 55.48000)
USGS Quad: CRAIG (B-2) Longitude: 132° 38.7' W (-132.64500)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: NO 5 1960
DESIGNATION: 945 0544 TIDAL 5
MONUMENTATION: Tidal Station disk VM#: 16715
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#:
SETTING CLASSIFICATION: Rock ledge OPUS PID:
LATITUDE: 55° 28.8' N ( 55.48000) LONGITUDE: 132° 38.7' W (-132.64500)
The bench mark is a standard disk set in rock outcrop bedrock 9 m (29 ft) east
of bench mark 2.
BENCH MARK STAMPING: 1X
DESIGNATION: 945 0544 TIDAL 1
MONUMENTATION: Tidal Station disk VM#: 16873
AGENCY: US Coast and Geodetic Survey
(USC&GS) IDB PID#:
SETTING CLASSIFICATION: Rock ledge OPUS PID:
LATITUDE: 55° 28.8' N ( 55.48000) LONGITUDE: 132° 38.7' W (-132.64500)
The bench mark is a disk set in a farly smooth rock ledge having flat sloping
face toward Hollis, the highest part of ledge is about 2 m (6 ft) inshore and
about 1m (3 ft) above the mark.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 5
Station ID: 9450544 PUBLICATION DATE: 09/05/2003
Name: HOLLIS ANCHORAGE, KASAAN BAY
AK
NOAA Chart: 17426 Latitude: 55° 28.8' N ( 55.48000)
USGS Quad: CRAIG (B-2) Longitude: 132° 38.7' W (-132.64500)
T I D A L D A T U M S
Tidal datums at HOLLIS ANCHORAGE, KASAAN BAY based on:
LENGTH OF SERIES: 2 MONTHS
TIME PERIOD: July 2002 - August 2002
TIDAL EPOCH: 1983-2001
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 = 4.840
MEAN HIGH WATER MHW = 4.564
MEAN TIDE LEVEL MTL = 2.525
MEAN SEA LEVEL MSL = 2.522
MEAN LOW WATER MLW = 0.485
MEAN LOWER LOW WATER MLLW = 0.000
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
3 5.008 0.444
2 4.613 0.049
NO 4 1953 5.479 0.915
NO 5 1960 4.985 0.421
1X 5.307 0.743
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 5
Station ID: 9450544 PUBLICATION DATE: 09/05/2003
Name: HOLLIS ANCHORAGE, KASAAN BAY
AK
NOAA Chart: 17426 Latitude: 55° 28.8' N ( 55.48000)
USGS Quad: CRAIG (B-2) Longitude: 132° 38.7' W (-132.64500)
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.