get_datums: Retrieve a named vector of tidal datums

In ccb60/SLRSIM: Tools to Analyse Sea Level Rise

Description

Retrieve information from NOAA on tidal datums and certain statistics describing the tidal regime at NOAA tide stations.

Usage

get_datums(.station, .units = "metric")

Arguments

.station	A number or string specifying the NOAA station for which to retreive metadata. A list of NOAA stations is available at https://tidesandcurrents.noaa.gov/stations.html?type=Water+Levels. A user-friendly map interface is available here: https://tidesandcurrents.noaa.gov/map/index.html?type=TidePredictions.
.units	Should values be returned in metric (default) or english units?

Details

Each tidal Station in the NOAA Station network measures (or estimates) water elevation at regular intervals (usually every six minutes, or ten times an hour). Raw elevations are referenced to a station-specific reference elevation, called the Station Datum. Usually, however, we want elevations expressed in units that can be interpreted in relation to tidal charts, topographic maps, surveyor's benchmarks or statistical summaries of water level, such as the mean height of all high tides.

The values returned by this function provide information on the relative elevation of different elevation reference frames, and thus facilitate interconversions.

The return value here includes all values provided by NOAA as part of their list of datums. The list of available datums may not always remain the same. Most tidal datums are defined as means over the period of the tidal epoch. A list of datums with descriptions is available from NOAA here: https://tidesandcurrents.noaa.gov/datum_options.html. Not all datums defined there are available via this function.

The primary values available include the following:

MHHW

Mean Higher High Water (mean of the higher high tide each day)

MHW

Mean High Water (mean of all high tides)

DTL

Mean Diurnal Tide Level (mean of MHHW and MLLW. Sometimes MDTL)

MTL

Mean Tidel Level. Mean of MHW and MLW. (MHW + MLW)/2)

MSL

Mean Sea Level. Mean of hourly tidal observations over the tidal epoch.

MLW

Mean Low Water

MLLW

Man Lower Low Water

GT

Greater Diurnal Range. (MHHW - MLLW)

MN

Mean Range of Tide. (MHW - MLW)

DHQ

Mean Diurnal High Water Inequality. Mean difference between the height of two daily high tides

DLQ

Mean Diurnal Low Water Inequality. Mean difference between the height of two daily low tides

HWI

Greenwich High Water Interval (hours). The average interval between the moon's transit over the Greenwich meridian and the following high water at a location

LWI

Greenwich High Water Interval (hours). The average interval between the moon's transit over the Greenwich meridian and the following low water at a location

NAVD88

North American Vertical Datum of 1988

Value

A named vector of numerical values. The names are the abbreviations for the tidal datum, facilitating data access.

The values are as provided by NOAA. The list includes several statistics of the tidal regime that are not reference elevations, but provide other information about the local tidal regime.

All elevation datums are referenced to the (arbitrary) Station Datum. Not all datums available on Station web pages are included. In particular, HAT, LAT, max and min tides are not included here. See the related get_hat() function for access to HAT.

See Also

Other station information access functions: get_availability(), get_epoch(), get_hat(), get_sl_trend(), get_tz()

Examples

# Retreive datums for Portland, Maine
portland_id <- 8418150
get_datums(portland_id)

ccb60/SLRSIM documentation built on Jan. 21, 2022, 1:31 a.m.