U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 6
Station ID: 9458293 PUBLICATION DATE: 07/02/2018
Name: CHIRIKOF ISLAND, SW ANCHORAGE
AK
NOAA Chart: 16580 Latitude: 55° 48.5' N ( 55.80830)
USGS Quad: KAGUYAK (D-5) Longitude: 155° 44.4' W (-155.74000)
To reach the bench marks by floatplane from Kodiak, proceed 306 km (190 mi) SW
to the small lake at the SW corner of Chirikof Island, then walk 0.5 km (0.3 mi)
west from the south end of the lake to the sand shoreline below the grass and
sand bluff. The tide station was located just below the bluff, SE of the first
rock outcrop. The bench marks are both above and below the bluff.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 8293 D 2006
DESIGNATION: 945 8293 D
MONUMENTATION: Metal Rod VM#: 18243
AGENCY: National Ocean Service IDB PID#:
SETTING CLASSIFICATION: Stainless steel rod OPUS PID#: BBBG99
LATITUDE: 55° 48.8' N ( 55.81330) LONGITUDE: 155° 44.4' W (-155.74000)
The primary bench mark is set back from a grassy bluff overlooking the sand
beach, 115.98 m (380.5 ft) SE of bench mark 945 8293 C, 106.16 m (348.3 ft) NW
of bench mark 945 8293 E, 71.60 m (234.9 ft) NE of the bluff, 65.70 m (215.6 ft)
south from the southwestern most of four wooden fence posts that are 2 m (6 ft)
tall, and 0.78 m (2.6 ft) SSE from a wooden witness post that is 2.2 m (7 ft)
tall. The datum point is set 7 cm (0.2 ft) below grade, being the top of a
stainless steel rod driven 10.8 m (35 ft) to refusal, and encased in an 18 cm
(0.6 ft) diameter NOS logo cap.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 6
Station ID: 9458293 PUBLICATION DATE: 07/02/2018
Name: CHIRIKOF ISLAND, SW ANCHORAGE
AK
NOAA Chart: 16580 Latitude: 55° 48.5' N ( 55.80830)
USGS Quad: KAGUYAK (D-5) Longitude: 155° 44.4' W (-155.74000)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 8293 A 2006
DESIGNATION: 945 8293 A
MONUMENTATION: Tidal Station disk VM#: 18244
AGENCY: National Ocean Service IDB PID#:
SETTING CLASSIFICATION: Rock outcrop OPUS PID:
LATITUDE: 55° 48.9' N ( 55.81500) LONGITUDE: 155° 44.6' W (-155.74300)
The bench mark is a set in the highest point of a rock outcrop that is 7.0 m (23
ft) long and 3.5 m (11 ft ) wide, 109.01 m (357.6 ft) NW of bench mark 945 8293
B, 73.8 m (242 ft) ESE of the base of the next rock outcrop along the beach, 5.6
m (18 ft) SSW of the adjacent rock face, and 4.4 m (14 ft) NNE of the seaword
extent of the rock outcrop and the edge of vegetation above the sand beach.
BENCH MARK STAMPING: 8293 B 2006
DESIGNATION: 945 8293 B
MONUMENTATION: Metal Rod VM#: 18245
AGENCY: National Ocean Service IDB PID#:
SETTING CLASSIFICATION: Stainless steel rod OPUS PID:
LATITUDE: 55° 48.9' N ( 55.81500) LONGITUDE: 155° 44.6' W (-155.74300)
The bench mark is set in grass covered sand at the base of a bluff overlooking
the sand beach, 109.01 m (357.6 ft) SE of bench mark 945 8293 A, 89.94 m (295.1
ft) WNW of bench mark 945 8293 C. 25.51 m (83.7 ft) on a slope SW of the top of
the grass sand bluff, and 17.40 m (57.1 ft) NE of the driftwood berm at the top
of the sand beach. The datum point is set 3 cm (0.1 ft) below grade, being the
top of a stainless steel rod driven 4.1 m (13.4 ft) to refusal, and encased in a
18 cm (0.6 ft) diameter NOS logo cap.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 6
Station ID: 9458293 PUBLICATION DATE: 07/02/2018
Name: CHIRIKOF ISLAND, SW ANCHORAGE
AK
NOAA Chart: 16580 Latitude: 55° 48.5' N ( 55.80830)
USGS Quad: KAGUYAK (D-5) Longitude: 155° 44.4' W (-155.74000)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 8293 C 2006
DESIGNATION: 945 8293 C
MONUMENTATION: Metal Rod VM#: 18246
AGENCY: National Ocean Service IDB PID#:
SETTING CLASSIFICATION: Stainless steel rod OPUS PID:
LATITUDE: 55° 48.9' N ( 55.81500) LONGITUDE: 155° 44.5' W (-155.74200)
The bench mark is set back from a grassy bluff overlooking the sand beach,
115.98 m (380.5 ft) NW of bench mark 945 8293 D, 89.94 m (295.1 ft) WNW of bench
mark 945 8293 B, 52.4 m (172 ft) WSW of the northwesternmost of four wooden
fence posts 2 m (6 ft) tall, 33.1 m (109 ft) ENE of a 7 m (23 ft) high bluff,
and 0.65 m (2.1 ft) south of a wooden witness post 0.9 m (3 ft) tall. The datum
point is set 9 cm (0.3 ft) below grade, being the top of a stainless steel rod
driven 10.9 m (36 ft) to refusal, and encased in an 18 cm (0.6 ft) diameter NOS
logo cap.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 6
Station ID: 9458293 PUBLICATION DATE: 07/02/2018
Name: CHIRIKOF ISLAND, SW ANCHORAGE
AK
NOAA Chart: 16580 Latitude: 55° 48.5' N ( 55.80830)
USGS Quad: KAGUYAK (D-5) Longitude: 155° 44.4' W (-155.74000)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 8293 E 2006
DESIGNATION: 945 8293 E
MONUMENTATION: Metal Rod VM#: 18247
AGENCY: National Ocean Service IDB PID#:
SETTING CLASSIFICATION: Stainless steel rod OPUS PID:
LATITUDE: 55° 48.8' N ( 55.81330) LONGITUDE: 155° 44.3' W (-155.73800)
The bench mark is set back from a grassy bluff overlooking the sand beach,
106.16 m (348.3 ft) SE of bench mark 945 8293 D, 66.51 m (218.2 ft) NE of the 4
m (13 ft) high bluff overlooking the beach, 26.5 m (87 ft) WNW of the top of a
small hummock that is 2 m (7ft) high and 10m (33 ft) wide at the base, 23.7 m
(78 ft) SW of a 2 m (7 ft) high bluff that runs ESE/WNW, and 0.95 m (3.1 ft) SSE
of a wooden witness post that is 1.6 m (5 ft) tall. The datum point is set 11
cm (0.4 ft) below grade, being the top of a stainless steel rod driven 12.1 m
(40 ft) to refusal, and encased in an 18 cm (0.6 ft) diameter NOS logo cap.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 6
Station ID: 9458293 PUBLICATION DATE: 07/02/2018
Name: CHIRIKOF ISLAND, SW ANCHORAGE
AK
NOAA Chart: 16580 Latitude: 55° 48.5' N ( 55.80830)
USGS Quad: KAGUYAK (D-5) Longitude: 155° 44.4' W (-155.74000)
T I D A L D A T U M S
Tidal datums at CHIRIKOF ISLAND, SW ANCHORAGE based on:
LENGTH OF SERIES: 3 MONTHS
TIME PERIOD: June 2006 - August 2006
TIDAL EPOCH: 2012-2016
CONTROL TIDE STATION: 9457292 KODIAK ISLAND, WOMENS BAY
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
MEAN HIGHER HIGH WATER MHHW = 2.673
MEAN HIGH WATER MHW = 2.419
MEAN TIDE LEVEL MTL = 1.435
MEAN SEA LEVEL MSL = 1.405
MEAN LOW WATER MLW = 0.452
MEAN LOWER LOW WATER MLLW = 0.000
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
8293 D 2006 12.684 10.265
8293 A 2006 7.094 4.675
8293 B 2006 7.285 4.866
8293 C 2006 14.283 11.864
8293 E 2006 13.221 10.803
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 6 of 6
Station ID: 9458293 PUBLICATION DATE: 07/02/2018
Name: CHIRIKOF ISLAND, SW ANCHORAGE
AK
NOAA Chart: 16580 Latitude: 55° 48.5' N ( 55.80830)
USGS Quad: KAGUYAK (D-5) Longitude: 155° 44.4' W (-155.74000)
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.