Reference
Data and methodology
SurfHog brings together observations published at different cadences and under different terms. This page explains how the records are selected, normalized, checked and summarized, and where the method cannot remove uncertainty.
Method and source terms last reviewed 21 August 2026.
Observation sources and reuse terms
Provider terms attach to the underlying measurements. SurfHog's presentation does not replace them or grant broader rights. This site does not provide raw observation downloads. Before reusing a provider-derived figure, check the linked current terms and preserve the named attribution.
| Provider | Terms | SurfHog note |
|---|---|---|
| Cefas WaveNet | Station-specific terms | Cefas identifies individual feeds as Open Government Licence, non-commercial use only, or unavailable for download. The station's own terms control reuse. |
| Channel Coastal Observatory | Open Government Licence | Use requires the attribution shown by the source for the relevant monitoring programme or station. |
| Met Office marine observations | WMO Essential data and Met Office terms | Marine observations are listed as WMO Essential and free of licence fee. Crown copyright and applicable Met Office terms still apply. |
| Met Éireann and Marine Institute | Creative Commons Attribution 4.0 | The Irish Wave Buoy Network ERDDAP dataset identifies CC BY 4.0 as its licence. |
| NOAA National Data Buoy Center | US government public data | SurfHog attributes NOAA and NDBC and links to the public source service. |
| CANDHIS, managed by Cerema | Licence Ouverte Etalab 2.0 | CANDHIS documents reuse under the French Open Licence with source attribution. |
| Kystdirektoratet | Reuse with source attribution | The Danish Coastal Authority permits use of its data with correct source identification; its service terms apply. |
| Puertos del Estado | Provider reuse conditions | Public access is free, but Puertos states purpose, attribution and onward-transfer conditions. Those conditions control reuse. |
| Rijkswaterstaat Waterinfo | Dutch government open-data terms | Waterinfo is the authoritative source. Check the current source notice before republishing its measurements. |
| Western Channel Observatory | Source terms | No general reuse licence is stated on the buoy page. SurfHog attributes the observatory and does not offer its raw feed for download. |
| Instituto Hidrográfico | Provider terms | No general reuse licence is stated on the public source page. Attribution and the provider's current terms apply. |
| Legacy SurfHog archive | Display and derived-summary use only | Older records retained by SurfHog do not carry a separate raw-data reuse grant. They are shown with provenance and are not downloadable in bulk. |
Processing observations
- Source timestamps are stored in UTC. Explicit offsets are converted to UTC; known legacy UK wall-clock records have been audited and normalized.
- Values are stored in SI units. Display conversions use 1 metre = 3.28084 feet, 1 metre per second = 2.23694 miles per hour, and Celsius to Fahrenheit = C × 9/5 + 32.
- When more than one enabled source represents the same canonical station and timestamp, source priority selects the preferred record and available fields are combined without overwriting populated higher-priority values.
- Report calculations use the stored precision. Rounding is applied only for display.
Quality checks
Source quality flags are retained. SurfHog also rejects implausible values and tests local changes, spikes and frozen sequences. Examples of hard limits include significant wave height above 12 m at inshore stations or 16 m offshore, wave periods outside 1 to 30 seconds, wind above 160 mph, and sea temperature outside -5 to 40 °C.
A rejected field is excluded without discarding unrelated fields in the same observation. Summary pages show how many values were checked and excluded. Automated checks can miss a sustained but plausible-looking sensor fault, so extreme records should still be verified against neighbouring values and the original provider.
Cross-station comparisons
Sources publish every 10, 30 or 60 minutes. To prevent a faster feed from receiving more weight, report comparisons first reduce each station to one accepted value per UTC hour. No values are interpolated across gaps. Regional figures then give each eligible station equal weight.
A report must state its completeness threshold. The 2025 almanac requires observations on at least 95% of calendar days and accepted values for a metric in at least 90% of the year's hours before that station contributes to the metric's comparisons.
Wave-power calculation
Provider-reported wave power is preserved as reported. SurfHog calculates a missing value only when both significant wave height and a genuine energy period are available. It does not substitute peak or mean period. The deep-water approximation is P = (ρg² / 64π) Hs²Te, using seawater density 1,025 kg/m³, gravity 9.80665 m/s², significant wave height Hs and energy period Te. Results are expressed in kilowatts per metre of wave crest.
Known gaps and limitations
- Buoys move, fail, change sensors and change operators. A canonical station record can span more than one deployment or source, which is documented where known.
- Nearshore and offshore stations measure different wave environments. A regional ranking is not a ranking of surf quality or coastal hazard.
- Coverage measures presence, not perfect accuracy. Unknown source quality flags and gaps in provider metadata remain visible limitations.
- Annual snapshots are reproducible summaries of data available when calculated. Later provider corrections or backfills can lead to a revised snapshot and update date.
Observed, forecast and calculated
- Observed
- A measurement published by a named station provider.
- Forecast
- A model estimate for a future or analysis time, labelled with its model and run.
- Calculated
- A value derived by SurfHog from stated inputs and a documented formula.