SEAiq includes support for various forms of tide and current data. It is always important to consider the source of your data. This is not intended as a complete description of tidal/current data. There are numerous references and other forms of documentation, including from the various data sources that SEAiq employs.
Tidal predictions from NOAA and CHS may be downloaded in advance in order that they are available even when you are offline. When you choose to download the data, it downloads at least several weeks of data. This is the procedure for setting this up:
Track Nearby Tide Stations (Only SEAiq Pilot) : When enabled, the next and previous tide stations along your route are calculated. Own-Ship must be following a route. To be selected, a station must meet the following conditions:
Interpolate Tide for Own-Ship (Only SEAiq Pilot) : When enabled, the water level at Own-Ship is estimated using linear interpolation based on relative positions along the route. Please understand that interpolation is based on the closest position of the route to the station. If a station is past the end of a route then then interpolation is based on the end-point of the route. Important: Depending on conditions, linear interpolation may not be an accurate method to estimate tides. Knowledge of local conditions should be used to evaluate accuracy of estimates. The following conditions must hold for this to be enabled:
Dynamic Tidal Adjustment (Only SEAiq Pilot) : When enabled and a tidal value is present for the current position of Own-Ship, an adjustment is made to chart display.
Alternately, a tide station can be opened and Select for Tide Adjustment pressed to manually select a tide station. This is disabled by pressing the disable (X) button in the status panel.
The tidal adjustment is applied globally to all charts based on the estimated value at Own-Ship's current position. Thus, viewing any chart showing water with different tidal levels than the current adjustment will be displayed erroneously.
This has the similar effect as manually editing Settings / Bathymetry / Tidal Adjustment. Please refer to documentation of that setting for more information.
When this feature is enabled, the tidal adjustment is automatically updated (eliminating any prior value). When this feature is disabled, the tidal adjustment is reset to 0 or No Adjustment (regardless of any prior value).
Dynamic tidal adjustment is only used if the sensor data is no older than the value of Tide Sensor Timeout setting (default: 15min).
When the value is changed, it is rounded down (never up) to the next lowest 5cm value. The chart display then only changes when the current estimated level is less than the adjusted value or more than 10cm above it. This means the adjustment is (1) always less than the estimated water level and (2) is no more than 10cm less.
Important: This feature must be used with care.
Use Set & Drift in Own-Ship Predictions (Only SEAiq Pilot) : When enabled, a panel is displayed with sliders for set and drift for current. This allows Own-Ship course predictions to account for set and drift, potentially increasing their accuracy. AIS targets are not affected. The set and drift are assumed to already be a component of Own-Ship's COG/SOG. This option only has an effect when the vessel turns; as the vessel turns the set and drift component stay fixed but the remaining components turn.
Enabling this feature disables the Trial Rate-of-Turn CHL feature.
Set Follows Route (Only SEAiq Pilot) : When enabled along with Use Drift in Course Predictions and following a route, the bearing of the route closest to Own-Ship is used for the set. This can be useful in rivers or other areas where drift is expected to roughly follow the direction of the route.
Note the set has a single fixed value for a particular position of Own-Ship at the current time and predicted movement of Own-Ship does not affect various course predictions. In other words predictions do not change set when, for instance, Own-Ship is following a curve.
USA (NOAA) Online Tides/Currents : Enables downloading a list of NOAA tide and current stations. You can select a station to get a link to official online data.
NOAA indicates tidal current predictions as being in Beta.
This requires an internet connection. However, you can download predictions so that they are available when off-line.
NOAA PORTS (Only SEAiq Pilot) : Enables download and display of NOAA PORTS data for many ports in the USA. The stations are identified using red diamonds with P. An attempt is made to update the stations every 6 minutes.
Please let us know if you are in an area with PORTS coverage that is not included in SEAiq.
Canada (CHS) Tides : Enables downloading a list of CHS tide stations. You can select a station to get a link to official online data.
This requires an internet connection. However, you can download predictions so they are available when off-line.
Canada SPINE Levels (CHS) (Only SEAiq Pilot) : Enables periodic downloading of tide interpolations that CHS creates. These are made using the SPINE method, described by CHS as follows: "The service web de prévisions et d’interpolation des niveaux d’eau (water level forecast and interpolation web service -- also called SPINE) is a system allowing one to obtain water levels at any time on the St. Lawrence navigation channel between Saint-Joseph-de-la-Rive and the Port of Montréal."
The requested position of forecasts correspond to location of buoys along the St Lawrence Seaway, which are treated as "virtual tide stations." Requests are made every 5 minutes. This requires an internet connection.
When SPINE is enabled, AIS water level values are ignored for purposes of the Track Nearby Tide Stations and related features.
Australian Tide Stations (AHO) (Only SEAiq Pilot) : Enables download of stations for Australia, Antarctic, and South Pacific. The stations are displayed as symbosl with links to online data. When enabled, an attempt is made to update these every day.
This requires an internet connection.
Norway Online Tides (Only SEAiq Pilot) : Enables downloading a list of stations for Norway. You can graphicly select a station to get a link to official online tidal data.
This requires an internet connection.
SHOM Online Tides (France) (Only SEAiq Pilot) : Enables display of predicted and real-time water level stations in France from SHOM (https://data.shom.fr).
This requires an internet connection.
AyeTides : Enables integration with the AyeTides and AyeTides XL apps. You can graphicly select a station to get a link the station.
Pressing the link switches to the AyeTides app and shows you data for that station. When done, you can press the back button in AyeTides to return to SEAiq.
This requires a purchase of AyeTides or AyeTides XL app. An internet connection is initially required to load the of stations. Once stations are downloaded, AyeTides can be used off line.
Show IHO S-111 Surface Currents (Only SEAiq Pilot) : When enabled, IHO S-111 Surface Currents products will be displayed.
This is an experimental feature. Not all variations of S-104 products may be supported. Please contact us if you wish to use this feature.
Show IHO S-104 Water Level (Only SEAiq Pilot) : When enabled, IHO S-104 Water Level products will be displayed.
This is an experimental feature. Not all variations of S-104 products may be supported. Please contact us if you wish to use this feature.
USA Offline Tides/Currents : Enables downloading harmonics for USA tides and currents. This data is based on NOAA developed harmonic constituents, but the harmonics may be somewhat out of date and should not be considered official.
This uses tidal data from XTide (http://www.flaterco.com/xtide). It is advertised as "NOT FOR NAVIGATION" and having "ABSOLUTELY NO WARRANTY." Further information can be found in the diagnostics information for individual stations.