Open tide data, combined into one dataset.
OpenTideConstants (OTC) combines official agency constants, constants that we fit from gauge records, and tide-model constants into one consistent dataset: one format, declared conventions, provenance for every record, and the accuracy of every station against official predictions. It is rebuilt automatically from the latest upstream data and released under CC BY 4.0. Every release is citable by one concept DOI and its datestamp.
Helgoland. TICON-4's mean time error here is 88–90 min. OTC's fit, with the time base corrected, is 6.7 min.
Three kinds of source, one release
Each source has its own licence, format and conventions. OTC reads each one with its own adapter, checks it, and writes everything into one format. At one location, official constants rank before a gauge fit, and a gauge fit before model constants.
See how tidal constants become a tide prediction in Tide Mechanics.
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Official constants
Published by the agency responsible for the gauge. Ranked first.
- NOAA CO-OPS
- Kartverket Norway
- LINZ New Zealand
- JMA Japan
- NOAA CO-OPS currents
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Gauge records that OTC fits
Sea-level records, fitted after the time-base checks. Ranked second.
- GESLA
- PEGELONLINE Germany
- Rijkswaterstaat Netherlands
- Marine Institute Ireland
- DMI Denmark
- SMHI Sweden
- FMI Finland
- SHOM REFMAR France
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Model constants
From a global tide model at station points, always labelled as model constants. Ranked third.
One OTC release
OTC_{YYYYMMDD}
- One format. JSON with a published JSON Schema, plus JSON Lines and CSV.
- Declared conventions for every constant set.
- Provenance for every record.
- Accuracy for every station against official predictions.
- Every set kept. A station lists every constant set, with one recommended by a published rule.
- SHA-256 checksums for every file, and one concept DOI for all releases.
Licence, attribution, access and coverage for each source are on Sources.
Why one consistent dataset matters
The German WSV gauge records in GESLA-4.0 are in German civil time but are labelled UTC. TICON-4 fitted them as they were, so its phases for those gauges are late. A dataset that combines sources must check every time base and convention before it uses them.
At Helgoland, TICON-4 has a mean time error of 88–90 min. OTC's fit of the same station, with the time base corrected, has 6.7 min.
Helgoland
One tide. Time of high water against the official prediction.
- Official prediction
- TICON-4, mean time error 88–90 min
- OTC fit from GESLA, mean time error 6.7 min
Each curve is the official curve shifted by that set's mean time error. All 11 stations and the method are on Validation.
What is different
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One dataset from many open sources
Official constants, constants fitted from gauge records and model constants, in one format. Every station has a stable id, its aliases in other systems (NOAA, GESLA, TICON, XTide, Kartverket, Slackwater), and every constant set from every source, with one recommended by a published rule.
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Accuracy for every station
Every release publishes, per station, how well the constants reproduce official predictions: time and height errors, missed and extra events, and the same numbers for the previous release.
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Declared conventions
Every set of constants states its phase reference, time zone, astronomical-argument model, nodal corrections and constituent definitions. A converter never guesses.
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Time bases checked
Every input record is checked for a wrong or undeclared clock. A clock is corrected only on positive evidence. A record whose time base cannot be confirmed is kept with the time base it declares, and is annotated as unverified or disputed.
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Automatic and current
Weekly watchers detect upstream changes. A build that passes all gates is published with no person in the loop. A build that fails keeps the last good release live.
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Open format
JSON first, with a published JSON Schema, plus JSON Lines and CSV. Every file is named
OTC_{YYYYMMDD}and comes with SHA-256 checksums. -
Open process
The site source and the issue tracker are public on GitHub. Anyone can report a problem with a station there.
Sources at a glance
| Source | What OTC takes | Licence | Rank |
|---|---|---|---|
| NOAA CO-OPS | Official constants and subordinate-station offsets | Public domain (US Government) | Official |
| Kartverket (Norway) | Official constants | CC BY 4.0 | Official |
| LINZ (New Zealand) | Official constants | CC BY 4.0 | Official |
| JMA (Japan) | Official constants (JMA-owned stations) | Public Data License 1.0 (CC BY 4.0 compatible) | Official |
| NOAA CO-OPS currents | Official tidal-current constants | Public domain (US Government) | Official (currents) |
| GESLA | Gauge records that OTC fits (derived constants only) | CC BY 4.0 on derived constants, per-provider attribution | Gauge fit |
| PEGELONLINE (Germany) | Gauge records that OTC fits | DL-DE->Zero-2.0 | Gauge fit |
| Rijkswaterstaat (Netherlands) | Gauge records that OTC fits | CC0 | Gauge fit |
| Marine Institute (Ireland) | Gauge records that OTC fits | CC BY 4.0 | Gauge fit |
| DMI (Denmark) | Gauge records that OTC fits | CC BY 4.0 | Gauge fit |
| SMHI (Sweden) | Gauge records that OTC fits | CC BY 4.0 SE | Gauge fit |
| FMI (Finland) | Gauge records that OTC fits | CC BY 4.0 | Gauge fit |
| SHOM REFMAR (France) | Gauge records that OTC fits (observations only) | Etalab Licence Ouverte 2.0 | Gauge fit |
| EOT20 | Model constants at station points | CC BY 4.0 | Model |
At one location, official constants rank before a gauge fit, and a gauge fit before model constants. Model constants are always labelled as such. Sources that were checked and not added are listed under Considered, not added. See Sources for licences, attribution, update cadence and coverage, Method for how each source is processed, and Why for the problems this project addresses.