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DataHub Automatic Polar Generation
DataHub Automatic Polar Generation
Jon Bilger avatar
Written by Jon Bilger
Updated over a week ago

DataHub Automatic Polar Generation

To take advantage of this feature you will need the following:

  • The DataHub needs to be connected to your NMEA 2000 instrumentation system, and outputing True Wind Speed, True Wind Angle and Speed over Ground

DataHub Polar Setup

  • Connect your laptop (Recommended) or mobile device to the DataHub Wi-Fi network. It will look like PW-Hub-XXXX in the list of available Wi-Fi networks on your device.

  • Open a Chrome or Safari browser and type in the URL bar.

  • Log in with username admin and password admin.

  • From the left menu select Polars, then click on the check box Automatic Mode, then Save & Apply

Now you will need to set your Base polar on the PredictWind Website.

The DataHub will average the NMEA data required for polar generation every 1 minute. These 1 minute averages are uploaded to the PredictWind server when a GPS tracking position is sent. Iridium have a minimum billing increment of 5KB, and so if you are only sending GPS tracking positions, and polar data there is no extra cost to uploading the polar data.

To start generating polars, you will need to set a base polar on the PredictWind Website.

  • Using a web browser on a PC or Mac, Login to then go to the Weather Routing Page.

  • From the Preferences tab, select "DataHub" as your boat type.

  • You will see a dialogue like the one below. While "Use my latest DataHub polar" is checked, the router will use your most recently generated DataHub polar. By deselecting the checkbox, you'll be able to see a list of all generated polars from the dropdown. Click Edit Base polar to get started setting your base polar.

  • Choose either Predefined or Advanced from the dropdown.

  • With Predefined, set the predefined polar using the dropdown box that appears to the right. Once you've found your boat everything is set including the boat dimensions. Click Save Base polar, to start generating polars.

  • With Advanced, you will need to fill out the table according to you polar, use the Import Polar button to import a polar.txt file from your computer. Next set the Boat Dimensions. From the dropdown box select either, Sail Monohull, Sail Catamaran, or Powerboat depending on your boat type. Next fill out the Displacement, Water-line-length (LWL), Beam and Canoe Body Draught (Draught). With everything set correctly, click Save Base polar to start generating polars.

  • It may take a few minutes for the server to generate the first version of your DataHub polar. After a few minutes, refresh the page, then calculate your first route using the DataHub polar. Each time our servers receive new data from your DataHub, a new DataHub polar will be generated, further refining the accuracy.

  • If you later decide that you set the wrong Base Polar, you can change and save it to something else. The server will start from scratch using all data we've received in the last 3 months to accurately generate a new DataHub Polar based on the modified Base Polar.

The polar data uploaded to the PredictWind servers are used to update your Base Polar in real time. Using a filtering technique, the AI algorithm decides if the data is representative of the yacht's performance in the given conditions and is useful in updating the polar. For example if polar data points are sent whilst you are at anchor, they will be discarded. Likewise if you are sailing but have the boat setup in a way that you are sailing much slower than normal it will also be ignored. As a rule the more data collected, the better the accuracy of the DataHub polar. So we recommend leaving this automatic polar generation feature on permanently.

The polar generation process uses GPS speed over ground (as requires no instrument calibration of a boatspeed sensor), and uses tidal current modelling (from our worldwide tidal current coastal model) to make corrections for the effects of current. In addition, the polar generation takes into account the effect of waves, by using the ECMWF wave model. Waves have a significant influence on the performance of the boat, but are not taken into account by traditional polars. So the format of this DataHub Polar is quite different taking into account Wind Speed, True Wind Angle and Significant Wave Height / Angle / Period from the ECMWF model. The inclusion of wave data is a technological breakthrough in polar generation, to give a more real-life representation of the boat's performance in all conditions. This DataHub polar can be used in the PredictWind weather routing for greater accuracy, and hence safety for the crew.

The generated polars will then be available in your PredictWind account under Weather Routing > Routing Preferences > DataHub Polars.

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