All tide data on bootitems comes from two government agencies. We don't change their numbers. We fetch them, store them, and show them in charts, tables and activity windows.
United States: NOAA CO-OPS
US tide predictions, water levels, currents and weather readings come from NOAA's National Ocean Service, Center for Operational Oceanographic Products and Services (CO-OPS).
What we use
- Tide predictions (high and low times and heights, and the predicted curve)
- Water level observations from live gauges, which report every 6 minutes
- Water temperature, wind and air pressure from the same stations, where fitted
- Tidal current predictions
- Station details and tidal datums
How we get it
From NOAA's public data API and metadata API. Predictions are refreshed on a schedule. Live readings are cached for a few minutes to keep the site fast and to avoid putting load on NOAA's servers.
Licence and credit
NOAA says information on its servers is in the public domain unless marked otherwise, and may be used freely. NOAA asks that its material be credited when reproduced. We credit NOAA CO-OPS on every US page and link each station page to the NOAA station page.
Credit line used on US pages:
Tide predictions and observations: NOAA National Ocean Service, Center for Operational Oceanographic Products and Services (CO-OPS).
NOAA provides its data "as is", without warranty. Live readings are preliminary and have not been checked by NOAA. They can contain errors or gaps.
NOAA did not create this site and does not endorse it.
Canada: Canadian Hydrographic Service
Canadian tide predictions and water levels come from the Canadian Hydrographic Service (CHS), part of Fisheries and Oceans Canada.
What we use
- Tide predictions (high and low water, and predicted heights)
- Observed water levels, where a station reports them
- Station details
How we get it
From the CHS Integrated Water Level System (IWLS) API. We stay within the CHS request limits and cache results.
Licence and required notice
We use CHS data under the CHS licence agreement. The licence requires the following notice. It appears on every Canadian page and here in full:
This product is not to be used for navigation. This product was made by or for the User Usman Yahya (bootitems.com) and contains intellectual property (Data) of the Canadian Hydrographic Service of the Department of Fisheries and Oceans. The copyrights in the Data are and remain the property of His Majesty the King in Right of Canada and shall not be sold, licensed, leased, assigned or given to a third party. The incorporation of the Data in this product does not constitute an endorsement or an approval of this product by the Canadian Hydrographic Service, the Department of Fisheries and Oceans or His Majesty the King in Right of Canada.
Other points from CHS:
- Data from the API may differ slightly from the official tide tables published each year by Fisheries and Oceans Canada. If they differ, the official publications prevail.
- Predictions reflect the latest information CHS had when we fetched them.
- Observed data carries quality flags. We hide readings that CHS flags as questionable.
Full licence: CHS licence agreement.
What we calculate ourselves
Some things on the site are our own work, built on the data above:
- Sunrise, sunset, twilight and moon phase. Calculated in code from the station's location. No outside service.
- Activity windows. Hour-by-hour scores for fishing, shelling and tidepooling, surfing and shallow boat launch. These are our opinion, based on tide height, tide movement, daylight and wind.
- Tide type and range. Worked out from a month or more of predictions.
- Spring, neap and king tide dates. Found by scanning each station's predictions. "King tide" is not an official term. We use the highest 2% of predicted high tides in a year.
- Nearby station offsets. The time difference between nearby stations' high tides.
- Curves at subordinate stations. NOAA gives only high and low times and heights for these stations. We draw the curve between them.
Errors in these calculations are ours, not NOAA's or CHS's.
Not for navigation
This site is for planning a day at the coast. Do not use it for navigation. For boating, use official NOAA or CHS products and nautical charts. See our disclaimer.
Report a problem
If a station looks wrong, contact us with the station name and what you saw.