U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Datums Page Page 1 of 6
Station ID: 9466153 PUBLICATION DATE: 04/08/2011
Name: SE OF HELMICK POINT, KUSKOKWIM RIVER
AK
NOAA Chart: 16304 Latitude: 60° 16.2' N ( 60.27028)
USGS Quad: BAIRD INLET (B-2) Longitude: 162° 24.6' W (-162.41017)
To reach the tidal bench marks from Bethel, proceed by charter float plane 68 km
(42 mi) SSW to a 180 m (591 ft) wide slough 4 km (2 mi) SE of Helmick Point,
taxi 270 m (886 ft) NNE up the slough. The bench marks are located on the east
bank of the slough and run from the bank of the first bend were the orientation
of the slough transitions from NW to ESE. The tide gauges were located
approximately 16 m (52 ft) from the east bank of the slough.
T I D A L B E N C H M A R K S
PRIMARY BENCH MARK STAMPING: 6153 A 2010
DESIGNATION: 946 6153 A
MONUMENTATION: Metal Rod VM#: 19684
AGENCY: National ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: stainless steel rod OPUS PID#: BBCC55
LATITUDE: 60° 16.2' N ( 60.27014) LONGITUDE: 162° 24.6' W (-162.40958)
The primary bench mark is set 362 m (1188 ft) up a 180 m (591 ft) wide slough
on the east bank of the Kuskokwim River, 25.44 m (83.5 ft) NNE of the grassline
that starts the high water flood plain, 14.52 m (47.6 ft) SE of a cluster of
trees, 10.85 m (35.6 ft) NW of another cluster of trees, and 8.59 m (28.2 ft)
NNE of a high water debris line with logs piled together from storms and ice
breakup. The datum point is 0.08 m (0.3 ft) below grade, being the top of a
rounded off stainless steel rod with a punch mark driven 10.8 m (36 ft) to
refusal and encased in a National Ocean Service logo cover.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 2 of 6
Station ID: 9466153 PUBLICATION DATE: 04/08/2011
Name: SE OF HELMICK POINT, KUSKOKWIM RIVER
AK
NOAA Chart: 16304 Latitude: 60° 16.2' N ( 60.27028)
USGS Quad: BAIRD INLET (B-2) Longitude: 162° 24.6' W (-162.41017)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 6153 B 2010
DESIGNATION: 946 6153 B
MONUMENTATION: Metal Rod VM#: 19685
AGENCY: National ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: stainless steel rod OPUS PID:
LATITUDE: 60° 16.2' N ( 60.27042) LONGITUDE: 162° 24.6' W (-162.41056)
The bench mark is set 386 m (1266 ft) up a 180 m (591 ft) wide slough on the
east bank of the Kuskokwim River, 70.25 m (230.5 ft) SE of bench mark 946 6153
C, 26.60 m (87.3 ft) NE of the high water line of the slough, 8.90 m (29.2 ft)
NE of the breakline where the vegetation changes flood plain to tall grass, and
5.78 m (19.0 ft) west of the brush line. The datum point is 0.12 m (0.4 ft)
below grade, being the top of a rounded off stainless steel rod with a punch
mark driven 12.0 m (40 ft) to refusal and encased in a National Ocean Service
logo cover.
BENCH MARK STAMPING: 6153 C 2010
DESIGNATION: 946 6153 C
MONUMENTATION: Metal Rod VM#: 19686
AGENCY: National ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: stainless steel rod OPUS PID:
LATITUDE: 60° 16.2' N ( 60.27075) LONGITUDE: 162° 24.7' W (-162.41178)
The bench mark is set 425 m (1394 ft) up a 180 m (591 ft) wide slough on the
east bank of the Kuskokwim River, 79.72 m (261.5 ft) SW of bench mark 946 6153
D, 70.25 m (230.5 ft) NW of bench mark 946 6153 B, 51.91 m (170.3 ft) ESE of the
grass edge, and 41.07 m (134.7 ft) west of the north point of a cluster of trees
running NW/SE. The datum point is 0.08 m (0.3 ft) below grade being the top of
a rounded off stainless steel rod with a punch mark driven 11.0 m (36 ft) to
refusal and encased in a National Ocean Service logo cover.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 3 of 6
Station ID: 9466153 PUBLICATION DATE: 04/08/2011
Name: SE OF HELMICK POINT, KUSKOKWIM RIVER
AK
NOAA Chart: 16304 Latitude: 60° 16.2' N ( 60.27028)
USGS Quad: BAIRD INLET (B-2) Longitude: 162° 24.6' W (-162.41017)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 6153 D 2010
DESIGNATION: 946 6153 D
MONUMENTATION: Metal Rod VM#: 19688
AGENCY: National ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: stainless steel rod OPUS PID:
LATITUDE: 60° 16.3' N ( 60.27108) LONGITUDE: 162° 24.6' W (-162.41081)
The bench mark is set 463 m (1519 ft) up a 180 m (591 ft) wide slough on the
east bank of the Kuskokwim River, 82.85 m (271.8 ft) SW of bench mark 946 6153
E, 79.72 m (261.5 ft) NE of bench mark 946 6153 C, 58.02 m (190.4 ft) NNE of the
north point of a cluster of trees running NW/SE, 48.20 m (158.1 ft) east of the
grass edge of the slough, 46.06 m (151.1 ft) NW of a small clump of trees, and
32.86 m (107.8 ft) NNW of another clump of trees. The datum point is set 0.05 m
(0.2 ft) below grade being the top of a rounded off stainless steel rod with a
punch mark driven 13.3 m (44 ft) to refusal and encased in a National Ocean
Service logo cover.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 4 of 6
Station ID: 9466153 PUBLICATION DATE: 04/08/2011
Name: SE OF HELMICK POINT, KUSKOKWIM RIVER
AK
NOAA Chart: 16304 Latitude: 60° 16.2' N ( 60.27028)
USGS Quad: BAIRD INLET (B-2) Longitude: 162° 24.6' W (-162.41017)
T I D A L B E N C H M A R K S
BENCH MARK STAMPING: 6153 E 2010
DESIGNATION: 946 6153 E
MONUMENTATION: Metal Rod VM#: 19689
AGENCY: National ocean Service (NOS) IDB PID#:
SETTING CLASSIFICATION: stainless steel rod OPUS PID:
LATITUDE: 60° 16.3' N ( 60.27178) LONGITUDE: 162° 24.5' W (-162.40897)
The bench mark is set 551 m (1808 ft) up a 180 m (591 ft) wide slough on the
east bank of the Kuskokwim River, 83.53 m (274.0 ft) NNE of a small clump of
trees, 82.85 m (271.8 ft) NE of bench mark 946 6153 D, 65.71 m (215.6 ft) south
of the high water line of the slough, and 43.25 m (141.9 ft) NNW of the
breakline where the vegetation changes from flood plain to tall grass. The
datum point is set 0.05 m (0.2 ft) below grade, being the top of a rounded off
stainless seel rod with a punch mark driven 12.1 m (39.7 ft) to refusal and
encased in a National Ocean Service logo cover.
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 5 of 6
Station ID: 9466153 PUBLICATION DATE: 04/08/2011
Name: SE OF HELMICK POINT, KUSKOKWIM RIVER
AK
NOAA Chart: 16304 Latitude: 60° 16.2' N ( 60.27028)
USGS Quad: BAIRD INLET (B-2) Longitude: 162° 24.6' W (-162.41017)
T I D A L D A T U M S
Tidal datums at SE OF HELMICK POINT, KUSKOKWIM RIVER based on:
LENGTH OF SERIES: 2 MONTHS
TIME PERIOD: July 2010 - August 2010
TIDAL EPOCH: 1983-2001
CONTROL TIDE STATION:
Elevations of tidal datums referred to Mean Lower Low Water (MLLW), in METERS:
MEAN HIGHER HIGH WATER MHHW = 3.104
MEAN HIGH WATER MHW = 2.518
MEAN SEA LEVEL MSL = 1.451
MEAN TIDE LEVEL MTL = 1.357
MEAN LOW WATER MLW = 0.196
MEAN LOWER LOW WATER MLLW = 0.000
North American Vertical Datum (NAVD88)
Bench Mark Elevation Information In METERS above:
Stamping or Designation MLLW MHW
6153 A 2010 3.838 1.320
6153 B 2010 3.498 0.980
6153 C 2010 3.425 0.907
6153 D 2010 3.338 0.820
6153 E 2010 3.249 0.731
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Ocean Service
Page 6 of 6
Station ID: 9466153 PUBLICATION DATE: 04/08/2011
Name: SE OF HELMICK POINT, KUSKOKWIM RIVER
AK
NOAA Chart: 16304 Latitude: 60° 16.2' N ( 60.27028)
USGS Quad: BAIRD INLET (B-2) Longitude: 162° 24.6' W (-162.41017)
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.