Data & methodology
What the map knows, and what it does not.
A Day in Ireland combines sources with different meanings and update schedules. The interface keeps observations, models, forecasts and local calculations distinct.
Freshness
Weather observations, radar, grid demand and official warnings are checked about every five minutes. Other island contexts refresh on their own schedules, from fifteen-minute marine and tide checks to a few-hourly satellite availability lookups. Current train positions are checked every minute, and public-transport vehicles every 65 seconds, where provider access and limits allow. Solar events use a bounded Dublin-day response and are reused for the current date. The official text forecast follows its issued timestamp and a short official-feed cache. River gauges update on the OPW's own cadence and may be delayed.
A timestamp describes the underlying observation or model time whenever the source provides one. Irish Rail positions are stamped at refresh because the realtime XML has no per-train observation clock. A service can be online while an individual measurement is older than expected.
River acquisition
OPW gauge readings are requested from waterlevel.ie. When that origin rejects ordinary Cloudflare Worker requests, the Worker may use Cloudflare Browser Run or a hosted bridge as a temporary fetch path. Those fallbacks are labelled in the interface; they do not change the meaning of the OPW levels, and they are not a second dataset.
Historical coverage and retention
History is collected every 15 minutes once collection begins. Fifteen-minute snapshots, the raw history tier, not copies of every provider payload, are kept for 30 days. Hourly rollups are kept for 12 months, and daily summaries are retained thereafter.
Exact cross-provider playback begins when collection starts. Missing provider observations and collection gaps remain missing; they are never inferred as zero. Hourly rollups and daily summaries describe the available observations rather than recreating every value that was visible at the time.
Transport history contains only national or route-level NTA summaries. It does not retain raw train or public-transport vehicle positions, vehicle identifiers or public messages. Radar and satellite image bytes are not archived, so historical imagery is not guaranteed.
Solar events and official forecast text are not retained in history v1; a historical view exposes an explicit gap rather than substituting today's sky or forecast.
Historical Iarnród Éireann / Irish Rail data is not retained while permission for archival and derivative display remains pending.
Calculated values
Transport speeds marked with ≈ are estimated from the distance and elapsed time between successive positions. Unrealistic jumps are rejected. ISS passes are calculated locally from published orbital elements. Neither should be treated as a provider-issued measurement.
Safety and limitations
River readings are gauge measurements, not flood warnings. Tide levels are not coastal-flood forecasts. Modelled air quality is regional guidance rather than a local sensor reading. Solar times describe astronomical events, not visibility. Aurora probability is not a promise of visibility. This project is not suitable for safety-critical decisions.
Sources
Attribution
Copyright Met Éireann; source met.ie; CC BY 4.0; presentation modified. Met Éireann forecast copy is shown verbatim after safe markup/entity normalisation and is displayed with current official warnings. Sunrise and lunar events are attributed to Sunrise-Sunset.org. Contains Irish Public Sector Information from waterlevel.ie, the Marine Institute and EPA. Road and boundary data © OpenStreetMap contributors, ODbL.
Contains NTA GTFS data © 2026 NTA, licensed under CC BY 4.0. Source: NTA Developer Portal. The data is aggregated and normalised by A Day in Ireland; changes were made. GTFS data is provided “as is”, and NTA is not responsible for errors or inaccuracies. A Day in Ireland is independent and is not endorsed by NTA.