Irish National Tide Gauge Network (INTGN) 02: Howth Harbour GLOSS Tide Gauges, Co. Dublin, Ireland 2017- Present

<strong>Howth Harbour GLOSS: </strong>

A tide gauge was installed on Howth Harbour in 2006 as part of the Irish National Tide Gauge Network, in conjunction with Fingal County Council as an extension to the Dublin greater area Flood forecasting and management system. From 2018 the gauge was permanently re-located due to pier works (from the middle to west piers).  
In 2020, the Global Sea Level Observing System (GLOSS) station(https://gloss-sealevel.org/sea-level-applications; https://uhslc.soest.hawaii.edu/gloss/) went live at the site. As a GLOSS requirement, there are three gauges co-located at the site. The primary gauge is named: “Howth Harbour GLOSS 1”, a second one “Howth Harbour GLOSS 2” for providing 100% redundancy and a third ‘B-Gauge’ that for calibration purposes, only measures from Mean Sea Level (MSL) and above. The Marine Institute have managed and funded the gauges throughout.  The GLOSS gauges are maintained, calibrated and characterised on a six-monthly rolling cycle and receive an annual classic land level survey to check wider area substrate stability. GNSS data are collected by the co-located, state of the art CGPS system. The MI manage the water level and land survey data, the GNSS data ate reported directly to SONEL (https://www.sonel.org/) from the site.
Howth Harbour was one of two GLOSS stations instigated, designed, implemented and maintained by the Marine Institute from 2019 to 2020 which went live in late 2020, the second being Union Hall Harbour. See this link for more details: https://data.marine.ie/geonetwork/srv/eng/catalog.search#/metadata/ie.marine.data:dataset.5331. The OPW operate the nation’s third GLOSS station at Portmore Pier, Malin Head. For detailed site-specific metadata and broader information about the tide gauge network, please see below.

<strong>Site-specific Metadata:</strong>
Installation date: 04/10/2017
Latitude: 53.392186
Longitude: -6.068010
Mean Sea Level, MSL (relative to Ordnance Datum Malin Head, ODMH) = -0.063 m
Lowest Astronomical Tide, LAT, relative to ODMH = -2.672 m
Tide Gauge Benchmark, TGBM, relative to ODMH = 3.285 m
Tidal range, between low and high mean spring tides = 3.732 m
Output parameters: 	
     –   Time, Latitude, Longitude, Station ID, Data source id
     –   Water level relative to ODMH (in metres)
     –   Water level relative to LAT (in metres)
     –   QC flag
Quality controlled data from: 19/01/2018
Automated Near-Real-Time Quality control and visual QC from: 01/09/2024
 

               <strong>Irish National Tide Gauge Network (INTGN) Real Time Data: </strong>

The INTGN is a network of tide gauges located around the Irish coast, collecting water level data to support the development of a permanent tidal monitoring infrastructure. The Marine Institute owns the network and is responsible for the service, maintenance, and quality control of all the network nodes. The Office of Public Works (OPW) and various local authorities contribute data from some additional gauges they have installed but these gauges are outside the control of network management, so are not included within the core MI dataset.

The home page for the network is www.irishtides.ie. It is accompanied by a core product, the on-line astronomical prediction system www.irishtides.ie/predict. 

Each tide gauge has a unique start date, deployment and service history. All the Marine Institute’s gauges are fully serviced, calibrated and operational. International best practice is observed in all operations and proactive maintenance activities.  Gauges will be down from time to time pending repair or reinstatement, as appropriate.

The following parameters are collected:
     –   Station
     –   DateTime
     –   Water Level (relative to Ordnance Datum Malin Head) *see caveats below
     –   Water Level (above Lowest Astronomical Tide [LAT]) *see caveats below

Data from each gauge is transmitted to the Marine Institute in real-time via mobile network connections, is quality controlled and made openly accessible. See below for more details.


               <strong>Quality Statement for TGN Data Processing: </strong>

Since September 2024, Real-Time data, streamed into the Marine Institute’s database every five minutes, undergoes automated quality control (QC) following QARTOD QC guidelines (https://ioos.noaa.gov/project/qartod/). The automated checks include:
     –   Time format validation
     –   Gross range check
     –   Spike test
     –   Rate of change test
     –   Flatline test
     –   Attenuated signal test
     –   Comparison with model-predicted tidal heights

The core principle of real time transmission and display of raw data on www.irishtideres.ie is maintained, and data are never deleted. Instead, each measurement is accompanied by a quality flag indicating whether it is has “no QC”, “good” or “bad” status (0,1 & 4 respectively), based on the SeaDataNet quality flagging system. A user can choose to use or ignore these flags depending on their use case for the data.

Approximately every one to two weeks, the data collected by each tide gauge undergoes visual screening by the Marine Institute’s Ocean and Climate Services Section. This process verifies automated flags and identifies any issues missed by the automated QC. A final visual QC flag is then applied. Prior to September 2024, all data was subject to a manual QC routine, which is also represented in the visual-QC flag record.

Users should be aware that the automated QC may flag data that are reasonable in scenarios where there is significant deviation from the normal tidal cycle (e.g. storm surge events). For this reason, the visual QC flag should supersede the automated QC flag when present. 

As part of an annual calibration and maintenance campaign, all Marine Institute tide gauges are serviced and calibrated. Accurate calibration, including sensor level adjustments, drift calculation and tidal cycle precision, is essential for producing high-quality data. Integration of calibration results into the data processing workflow is ongoing. Until this is complete and corrections are applied, where needed, the Marine Institute cannot fully quantify margins of error and can therefore only partially endorse the final data outputs. Despite extensive calibration and QC efforts, unresolved offset issues should be considered a caveat for users requiring high-accuracy data over the full time-series. Another caveat is that from the reported parameter “Water Level (above Lowest Astronomical Tide [LAT])”, the LAT values are model derived, due to not having enough observations (> 19 years) to calculate LAT in most cases.

If users encounter specific issues affecting the intended use of these data, they may contact the Marine Institute for support. The Institute will review and address such cases individually, based on the nature of the concern.

<strong>Data access: </strong>
Data is available via the Marine Institute’s ERDDAP download portal: https://erddap.marine.ie/erddap/tabledap/IrishNationalTideGaugeNetwork.html Below are some examples of how a user can customise a download from ERDDAP:
     –   Filter data by quality flag
     –   Select specific gauges
     –   Choose date ranges
     –   Specify file output formats

Real-time data is also accessible from an SFTP site associated with www.irishtides.ie. Please get in touch for information on accessing the SFTP site.

Tags: environment
Organization: Marine Institute