Tide Level Data from NOAA; Time of High/Low Water, Hourly Heights, and Monthly Means; Bench Mark Sheets with Tidal Datum ReferencesEntry ID: OES_OLLD_TIDES
Abstract: The National Ocean Service maintains a long-term data base containing water
level measurements and derived tidal data for coastal waters of the United
States and U.S. territories. These data allow for the determination and
maintenance of vertical reference datums used for surveying and mapping,
coastal construction, waterborne commerce, water level regulation, marine
boundary determination, and ... tide prediction, and for the determination of
long-term water level variations (e.g. trends). The data also support other
U.S. government programs, including the National Weather Service (NWS) Tsunami
Warning System, the NWS storm surge monitoring programs, and the NOAA Climate
and Global Change Program.
The data base contains an extended series of water level measurements recorded
at different tide observation stations. These data are processed to generate
a number of products, including monthly and yearly averages for mean tide
level, mean sea level, diurnal tide level, mean high and low water, mean
range, diurnal mean range, monthly extremes for high and low waters, and
frequency and duration of inundations (the number of times and length of time
at which the water level has equaled or exceeded a specific elevation for a
period of analysis).
Data are compiled for coastal waters of the United States, Puerto Rico, the
Virgin Islands, and U.S. territories in the Pacific region. Water levels are
monitored from a network of over 150 permanent, continuously operating tide
observation stations and from numerous stations operated for short-term and
Water level measurements are compiled for a variety of observation periods,
depending upon the location. For some tide observation stations, records date
back to the late 1800s. Observed water level values are compiled primarily at
six minute increments, however, some stations provide real-time data for
planning and emergency situations. The observed values are processed to
generate mean and extreme values for different temporal intervals, as noted
The data consist simply of elevations of water, in feet, observed at specific
geographic locations and temporal periods. All water level measurements are
referenced to staff '0' and can be referenced to other datums, such as the
National Geodetic Vertical Reference Datum of 1929 (NGVD). Recent data are
recorded to the hundredth of a foot; data collected prior to the mid-1960s are
recorded to the tenth of a foot.
The foundation of the the water level data base is the National Water Level
Observation Network (NWLON), a system of long-term operating tide stations
maintained by NOS. Data also are obtained through short-term and long-term
cooperative projects with other federal, state, and local agencies and
governments to accomplish mutual goals in water level measurement. For
example, tide stations are operated temporarily for marine boundary
determination and hydrographic survey projects. NOS also maintains several
cooperative stations with foreign governments for the Climate and Global
Indexes of tide stations maintained by NOS are available which include for
each station the latitude, longitude, dates of observations, bench mark sheet
publication date, and tidal epoch. NOS also issues tidal bench mark sheets
upon completion of a data collection series or as needed for long-term NWLON
stations. Tidal bench mark sheets provide location descriptions and vertical
elevations referenced to tidal datums of the station bench marks. A table of
tidal datums and the 1929 NGVD, when available, are referenced to the station
A number of products are issued monthly and annually, for free or on a cost
recovery basis. The products are distributed on either hard copy, 5.25 inch
floppy, or digital magnetic tape, and include the following:
o Tide Observation Station Lists
o Tides, 6-Minute Heights
o Tides, Hourly Heights
o Tides, Times and Heights of High and Low Waters
o Tides, Monthly Mean Summaries
o Tidal Bench Mark Sheets with Tidal Datums
o Frequency and Duration Analysis of Tidal Water Levels
o Daily Mean Sea Level
Real-time and near real-time water level data are available from selected
stations equipped with telephone telemetry. To obtain these data, users
require appropriate receiving and computer hardware and a specialized software
package, Tides ABC, distributed by NOS.
Real-time data are also transmitted to the Ocean and Lake Levels Division and
are distributed in limited quantities, in near real-time to users with
appropriate receiving hardware. These data are available in the following
o Daily Remote Station Report - A formatted report of all data collected at a
station on the previous day.
o Storm Surge Bulletin - The most recent 1 to 6 hourly water levels collected
at a station, provided within 15 minutes of a reporting period.
o Tsunami/High Speed Sample Bulletin - Data collected at a faster sampling
rate, provided within 5 minutes of each 15 minute reporting period (limited to
only a few West Coast Stations).
The Ocean and Lake Levels Division also provides a number of information
services for which it charges a fee, based on a professional service rate of
$30.00 per hour. The services include the following:
o Computation of bench mark elevations and tidal datums.
o Computation of the NGVD referenced to other tidal datums.
o Computation of historical tidal datums.
o Providing tidal zoning for hydrographic projects.
o Preparing and reviewing certified documents for court use.
Information about individual water level stations may be obtained from
the NOS MapFinder. The NOS MapFinder features a spatial index and
corresponding water level summary sheets for 103 NWLON stations in
coastal areas. This information includes geographic station location,
descriptive location text, collected data types, and date of the
earliest collected water level data. In future years, additional
stations will be added to the service.
(Click for Interactive Map)
ISO Topic Category
Role: TECHNICAL CONTACT
Phone: (301) 713-2877
NOAA/National Ocean Service Oceanographic Products and Services Branch 1305 East-West Highway, SSMC4
City: Silver Spring
Province or State: MD
Postal Code: 20910-3281
Creation and Review Dates
Last DIF Revision Date: 2006-11-20