SEAiq supports overlaying weather data on charts. The data that is displayed can be either automatically downloaded (requires an internet connection) or manually installed by you (useful if you are on passage). Currently, wind direction/strength and pressure can be displayed.
Wind is depicted using arrows showing the direction and speed of the wind at various data points. The location corresponding to the prediction is indicated with a tiny circle at the mid-point of the arrow. Speed is shown using feathers along the shaft of the arrow. Knots are always used for wind speed, regardless of other display settings you may have made. There may be any number of long feathers, each indicating 10kn of wind speed. A short feather indicates an additional 5kn of wind speed. Speeds are rounded up to the next 5kn. 22kn is displayed the same as 25kn: 2 long feathers and 1 short one.
If you want the original information about a data point, you can double tap on the center of an arrow and select "Details for this Location." Along with other information about the GRIB file, you will see the direction and speed predicted for the location you selected.
Note that times shown for weather data are in local time unless specified otherwise.
Automatic download is the preferred method for when you have a reliable internet connection. SEAiq will automatically download weather data for the areas that are visible on the chart display. As you pan the display, it will automatically download data for new areas that are displayed.
Using this feature simple:
SEAiq downloads the NOAA GFS 0.5x0.5 degree forecasts from http://nomads.ncep.noaa.gov. These forecasts are updated every 6 hours. Data is downloaded for 10x10 degree blocks for the visible area of the display. After current data for the visible area is displayed, it progressively downloads more forecasts, in 6 hour increments, for up to 7 days.
Whenever automatic download is enabled, SEAiq will be using internet bandwidth to download and update the GRIB data. Once SEAiq has downloaded all forecasts for the current display then it will stop downloading, until you move the display to a new area or new forecasts become available.
Important: we strongly recommend testing this feature before heading out on passage to ensure everything works. Ideally, you should test it using your SSB/Pactor just as you would at sea.
This method of viewing GRIB files is useful for situations where you will not have a normal internet connection (such as when on passage or in remote locations) but you do have an alternate method of acquiring GRIB files (such as Single Sideband radio with Pactor Modem or Satellite phone).
Weather data is exchanged using files in a standard format called GRIB. GRIB stands for "Gridded Binary". SEAiq requires GRIB files to end in ".GRB" or ".grb".
You can request GRIB files via email from SailDocs following their instructions or the instructions here. If you are at sea, you will probably want to use the AirMail program to request the data. It is fine if other weather data is included besides wind and isobar, but only wind and isobar will be shown.
The instructions below assume you will use an email formatted by the Request GRIB from SailDocs button in SEAiq. If you are using an different method, then you can skip the first few steps.