…and a phone to steer her by

Mobiles have had a bad press as navigational tools, but if I were forced to choose one single piece of electronics to take to sea it would be my phone. That’s not a popular view among professionals.

Instructors and rescue services learn of many cases where boat owners, especially of powerful motor yachts and RIBs, set off for the open sea with nothing beyond a chart app on a mobile phone, and no knowledge of the underlying skills needed to navigate safely. For the Royal Yachting Association, mobiles are well down the list of recommended priorities, because of the risk that they will be used badly.

This view is reflected in the Royal Institute of Navigation’s book on electronic navigation for small craft#, which was written jointly with the RYA and the coastguard and published in December 2020. Using GNSS* as the new generic term for satellite systems, the book says:

“Increasingly mobile devices have built in GNSS receivers. In addition, many use a combination of GNSS with mobile phone base stations, Wi-Fi, Bluetooth and other sensors to generate a ‘blended’ position. Such devices are programmed to prioritise continuous position availability over accuracy. If GNSS is lost or degraded, the position calculation is derived from the other, less accurate, sensors.

At sea, mobile phone positioning uncertainty will typically be several hundred meters or more, which may be enough to put us into danger.” 

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