Datums for 9439201, St Helens OR


Columbia River Datum Columbia River Datum (CRD) is the adopted fixed low water reference plane for this area. CRD is a U.S. Army Corps of Engineers non-tidal datum defined at distinct river miles relative to NAVD88, and is used as chart datum above river mile 23 on the Columbia River. Datums are computed using observations from the low river stages of the year, generally August through October due to the masking of the tidal signal from strong seasonal river runoff during other portions of the year. Depending on river flow, water levels can be significantly higher than Columbia River Datum. As of 2014, the U.S. Army Corps of Engineers provided updated offsets for CRD that have been applied to this station. Station Datum (STND) is no longer set equal to CRD.
NOTICE: All data values are relative to the MLLW.

Elevations on Mean Lower Low Water

Station: 9439201, St Helens, OR
Status: Accepted (Jun 16 2017)
Units: Feet
Control Station: 9439040 Astoria, OR
T.M.: 0
Epoch: 1983-2001
Datum: MLLW
DatumValueDescription
MHHW3.23Mean Higher-High Water
MHW2.75Mean High Water
MTL1.49Mean Tide Level
MSL1.49Mean Sea Level
DTL1.62Mean Diurnal Tide Level
MLW0.23Mean Low Water
MLLW0.00Mean Lower-Low Water
NAVD88
STND-2.05Station Datum
GT3.23Great Diurnal Range
MN2.52Mean Range of Tide
DHQ0.49Mean Diurnal High Water Inequality
DLQ0.22Mean Diurnal Low Water Inequality
HWI0.04Greenwich High Water Interval (in hours)
LWI7.86Greenwich Low Water Interval (in hours)
Max TideHighest Observed Tide
Max Tide Date & Time Highest Observed Tide Date & Time
Min TideLowest Observed Tide
Min Tide Date & Time Lowest Observed Tide Date & Time
HAT6.06Highest Astronomical Tide
HAT Date & Time12/30/1986 23:24HAT Date and Time
LAT-1.79Lowest Astronomical Tide
LAT Date & Time04/25/1999 03:48LAT Date and Time
Tidal Datum Analysis Periods
08/01/2002 - 11/30/2002
07/01/2003 - 11/30/2003
07/01/2004 - 11/30/2004
08/01/2005 - 10/31/2005
08/01/2006 - 10/31/2006
08/01/2007 - 11/30/2007
08/01/2008 - 10/31/2008
08/01/2009 - 10/31/2009
08/01/2010 - 10/31/2010
09/01/2011 - 12/31/2011




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