Data sources

FishDataPoint does no measuring of its own. Here is where every number comes from, what we use it for, and its limits.

Astronomy: calculated by us

Astronomy Engine (open source, MIT licence) by Don Cross. We use version 2.1.19.

Used for: sunrise and sunset, moonrise and moonset, the moon overhead and underfoot, moon phase and illumination, twilight. Solunar windows are built from these events using our own published rule; see methodology.
How: calculated by our own code: in advance, when we build the site each day, for our reviewed places over the coming weeks; and in your browser for places you search or dates outside that range. No outside service is called, so astronomy keeps working even if every data service is down.
Limits: the calculations assume a sea-level observer and a flat horizon. Our sunrise and sunset times were checked against the U.S. Naval Observatory for a sample place and date and agreed to within two minutes.

Weather: Open-Meteo

Weather data by Open-Meteo.com, licensed under CC BY 4.0.

Used for: hourly air temperature, wind speed, wind gusts, wind direction, chance of rain, cloud cover, sea-level pressure and conditions codes, plus daily highs and lows calculated from those hours.
What it is: output from numerical weather models, served for the model grid cell nearest each place. These are forecasts and model estimates, not measurements from a weather station.
Range: about 7–8 days ahead. Beyond that we show no weather.
Limits: model grid cells are often a few kilometres across, so coastal, valley and mountain spots can differ from the forecast. We request times in UTC and convert them to the place's local time.
Access: we use Open-Meteo's free API, which is for non-commercial use. FishDataPoint has no ads, subscriptions or paid features, so it qualifies (D43). We'd move to a commercial Open-Meteo plan before adding any of those.

Place search: Open-Meteo Geocoding

Open-Meteo Geocoding API, which draws on GeoNames data.

Used for:
- turning a typed place name into coordinates and a time zone when you search for somewhere outside our reviewed places
- looking up a chosen result's name again from its GeoNames ID (the gid in the page address)
Time zone for a point: for a located point, or a typed address with no search result, your browser asks Open-Meteo's forecast API for the time zone at those coordinates (no weather variables). Without a time zone we can't tell which day it is there, so the page says "Location temporarily unavailable" rather than guessing.
Limits: search results are town and landmark centres, not fishing spots. Their pages say "Town centre, not a fishing spot". Pages for your own location or typed coordinates say "Selected point (rounded to about 100 m), not a reviewed fishing spot". Our 10 reviewed places use access points we chose by hand.
Directly from your browser: searches and point lookups go straight from your browser to Open-Meteo. We don't receive or store them. See privacy.
No duplicates: a search result is left out when it has the same name as one of our reviewed places and lies within 10 km of it, so you get the reviewed page instead. Our forecast points are piers and ramps, a few kilometres from the town centre the place-name service returns.

Tides: NOAA CO-OPS

NOAA Center for Operational Oceanographic Products and Services (CO-OPS). This is U.S. government data in the public domain. Source credit: NOAA/NOS/CO-OPS.

Used for: high and low tide times and heights, and hourly predicted heights for the tide chart.
What it is: predictions calculated from each station's harmonic constants. They are not live readings. Heights are relative to Mean Lower Low Water (MLLW).
Stations we use: listed per place on the coverage page, with links to NOAA's own station pages. Predictions for these stations are built into our site's files and refreshed each day when we rebuild the site, so your browser doesn't contact NOAA.
Limits: a prediction can't account for storms, wind setup or river flow. A station can be a few kilometres from your spot. Tide predictions don't include current speed or direction.

Coastal sea conditions: Open-Meteo Marine

Open-Meteo Marine Weather API (CC BY 4.0), using Open-Meteo's best-match wave model for each cell.

Used for: hourly wave height, period and direction, plus swell height, period and direction where the model provides swell, shown in a "Sea conditions" panel.
What it is: modelled sea state, not observations. Values describe an offshore model grid cell, and the panel shows which cell (its coordinates). Conditions at the shore, on a pier or in a harbor can be quite different.
Where: open-coast reviewed places only (Pacific Beach, Santa Monica Pier, Santa Barbara, Monterey). Sheltered bays and harbors (San Diego Bay, San Pedro inside Los Angeles Harbor, San Francisco Bay) show "Not applicable — sheltered bay", because the open-ocean model doesn't describe them. Lakes have no sea panel. Searched locations show "Not available for searched locations".
Range: about a week ahead, like the weather.
Limits: not a surf report or a safety assessment. Check NWS marine forecasts and local conditions before going out.

Lake level: U.S. Geological Survey (Lake Tahoe only)

U.S. Geological Survey gauge 10337000, "Lake Tahoe at Tahoe City", read through the USGS Water Data OGC API (api.waterdata.usgs.gov). This is U.S. government data in the public domain. Cite as: U.S. Geological Survey, National Water Information System, doi:10.5066/F7P55KJN.

Used for: the latest lake elevation on the Lake Tahoe page, for example "6,226.70 ft (Lake Tahoe datum, USBR)", with the gauge's raw gage height, the time of the reading, the source and gauge, and the data's approval status (e.g. "provisional").
What it is: a reported water level. Recent USGS readings are usually provisional and can be revised later.
Older readings: if the latest reading is more than 48 hours old, it is marked "older reading".
No ramp advice: a lake level doesn't tell you whether a boat ramp is open or usable. Check ramp status with the operator.
Other lakes: Shasta Lake and Big Bear Lake show "Lake level not available for this lake" for now. Searched locations show no lake level.
Freshness: your browser fetches the latest reading from USGS when you open the page. If USGS can't be reached, the card says the level is temporarily unavailable.

Official weather alerts: National Weather Service

National Weather Service API (api.weather.gov, NOAA), public domain. Your browser requests alerts directly from the NWS.

Used for: active official alerts (for example small craft advisories, high surf or winter storm warnings) for the NWS zones each reviewed place sits in: its forecast zone, its county and, for coastal places, its marine zone. We looked these up once per place.
Shown: the event, severity, issuing office, the areas it covers, when it starts and ends (or, if the NWS gives no end time, when the message expires), the headline and the NWS instructions word for word, with a link to the full alert on weather.gov. Only current, real alerts are shown (no tests or exercises, nothing already expired), most severe first. Alerts with the same event and severity (usually one per zone) are grouped into one item that lists their areas. Severe and Extreme alerts start expanded.
Freshness: your browser checks for alerts when you open the page, and again every 5 minutes while it stays open. If the NWS can't be reached, the page says "Alert status unknown".
When nothing is active: "No active NWS alerts for this area as of {time}".
When we can't check: if the alert service can't be reached, or we've switched alerts off, the page says "Alert status unknown" and points you to weather.gov. That never means there are no alerts.
Where: all 10 reviewed places. Requests name the zones, never a location. Searched locations say "Official NWS alerts are not available for searched locations".
Limits: a zone covers a wide area, so an alert may not apply to your exact spot, and an alert can appear on weather.gov a few minutes before it shows here. Always check weather.gov and local marine forecasts before going out.

How live data reaches your page

The site is static files served by Cloudflare. We run no server that fetches, stores or logs data for you.
Your browser fetches live data directly from Open-Meteo (weather, sea conditions, place search, time zones), the National Weather Service (alerts for our reviewed places' zones) and the U.S. Geological Survey (Lake Tahoe level). Tide predictions are built into the site's files each day, so your browser never contacts NOAA. These services see your IP address and what was requested; see privacy.
If a service is slow or down, only its card is affected: it says the data is unavailable (for alerts, "Alert status unknown"), and everything else keeps working. We don't keep older copies to show instead.
Any data service can be switched off for the whole site when we rebuild it; its cards then say the source is switched off. Astronomy, calculated by our own code, always works.
Your browser may reuse a recent answer from its normal web cache, as each service allows.
Calendar (.ics) and PDF downloads are created in your browser from the data on the page, so they make no extra requests.
Offline copies are kept by your browser. Opening one makes no request to us or any data service, so its data is only as fresh as the time shown.

What we don't use

No proprietary solunar or "bite" ratings from other sites.
No paid worldwide tide service. Tides are covered only at the U.S. NOAA stations listed on the coverage page.
No map tiles yet.

Spotted a data problem? Tell us via the contact page.