NOAA Data (Tides, Currents, Charts)

The National Oceanic and Atmospheric Administration (NOAA) is the primary data source for BoatRoutes’ US water coverage. We use several NOAA programs and datasets.

CO-OPS: Tides and Currents

NOAA’s Center for Operational Oceanographic Products and Services (CO-OPS) operates a nationwide network of tide and current measurement stations. BoatRoutes uses two types of CO-OPS data:

Tide Predictions

CO-OPS provides tide height predictions for hundreds of stations along the US coast. These predictions are calculated from harmonic constants — mathematical models of the gravitational forces of the moon and sun that drive tides.

How we use tide predictions:

Display tide height curves on station detail pages
Color-code route overlays by tide height at each point along the route
Show high/low tide times and heights in station sparkline cards

Reference datum: All tide heights are referenced to MLLW (Mean Lower Low Water), which is the average of the lower of the two daily low tides. This means charted depths assume MLLW conditions, and positive tide heights indicate more water than charted.

Current Predictions

CO-OPS also provides tidal current predictions for key stations, including many in Puget Sound, the San Juan Islands, and the Strait of Juan de Fuca.

How we use current predictions:

Display current speed and direction on route overlays
Show daily current curves with slack water times on station pages
Calculate current impact summaries for route planning

Current data includes:

Speed in knots
Direction (flood vs. ebb, with bearing)
Slack water times (when current reverses)
Maximum flood and ebb speeds

Station Types

Harmonic stations — full prediction based on direct observations. Most accurate.
Subordinate stations — predictions derived from a nearby harmonic station using time and height/speed corrections.

NOAA ENCs

NOAA produces Electronic Navigational Charts (ENCs) in the international S-57 standard. These vector charts contain detailed information about:

Coastline geometry
Depth contours and soundings
Navigation aids (buoys, beacons, lights)
Rocks, wrecks, and obstructions
Restricted and prohibited areas
Anchorage areas

Learn more about how we use ENCs

NOAA Raster Charts

NOAA’s raster navigational charts (RNCs) are the digital versions of traditional paper charts. BoatRoutes uses these as map tile overlays so you can view familiar chart imagery on the interactive map.

These tiles are served via NOAA’s tile server and always reflect the latest chart edition.

Note: NOAA is ending its raster chart program. Once it shuts down, these raster tiles may stop updating.

Data Accuracy and Limitations

Predictions vs. observations: Tide and current predictions are based on astronomical forces (moon and sun positions). Actual conditions can differ due to:

Wind and barometric pressure changes
Storm surge
River runoff (especially in spring)
Seiche effects in enclosed waterways

Chart currency: NOAA updates ENCs regularly through Notices to Mariners. Our navigation grid is updated when new chart editions are released, but there may be a lag between NOAA publication and our processing.

Station coverage: Not every waterway has a current station. In areas without nearby stations, current predictions are less reliable. BoatRoutes uses the nearest available station data, but conditions may differ from the actual station location.