Using a sextant, the latest nautical almanac, some calculations and some tabulated data it is possible to make a position fix without the use of electronic navigational aids. However with a GNSS display giving an instant position fix at a glance, it is obvious why GNSS is now the standard in ocean navigation. It is quicker, provides a real-time position and is less affected by weather.
Although both methods of navigation are similar in principle, the method of calculation is extremely different, the requirements for functionality are different and the opportunities for error are also different. With the increasing reliability and availability of GNSS the question needs to be asked as to how important celestial navigation is today.
It is important to understand this for several reasons. For example, could an officer or yachtsman who has not practised celestial navigation for a long period remember the processes and calculations involved in a real life situation? If not, it could be a major risk to the safety of the ship and any lives on board.
A study in 2002 showed that 71% of maritime accidents can be attributed to a lack of situation awareness. This means that seafarers don't always know what's going on. Instinct may tell us that GNSS can only help this but perhaps we'll find that over-reliance is actually compounding the problem.
Here's a few reasons why I believe Astro navigation is still relevant today... Situational Awareness: If the role of position fixing is left solely to electronic equipment then the navigator will not have the intimate awareness associated with traditional fixing methods. Automation Complacency: A well documented phenomenon, described as; the assumption that everything is fine unless a warning alerts you to a problem. This is considered among the Top 5 contributing factors for aviation accidents. Automation bias: A term used to describe reliance on 'decision aids'. Decisions are made by the equipment operator without making a full appraisal by using all available information.
In 1995 the cruise ship, Royal Majesty, grounded on the way to Bermuda, the GPS system had a fault that had not been noticed by the officers. The vessel continued unaware, plotting Dead Reckoning positions that were being displayed by the GPS unit, until the grounding occurred 16.5 miles from where the officers thought they were. This is a prime example where automation has resulted in navigating officers blindly plotting GPS positions, resulting in catastrophe. The issue is that when a system appears to be as reliable as GPS, the awareness of the navigator drops and reliance increases.
It is clear that there are problems occurring during the transition as we move towards a future of electronic position fixing and e-navigation. Research has shown that as the navigator is supplied with more equipment to automate tasks, awareness of the current situation drops. GNSS is just one piece of equipment found on a modern bridge, but since a large proportion of the equipment on the bridge take a GNSS input it seems important to consider this as an integral part of the modern bridge.
It has been found that the GNSS system of navigation is highly susceptible to interference and that this interference can lead to confusion for the seafarer. On top of this, problems with the receiver, such as antennae failure, can go unnoticed by the navigator and DR positions may end up being plotted as position fixes, as with the Royal Majesty. It has been proven that it can be dangerous to rely on some data due to the inherent weaknesses of the systems from which the data is derived. While solutions such as eLORAN could help to overcome these problems they still do not address the overall problem with situational awareness.
So, for now at least, it seems wise for navigators on any type of vessel to keep aware and keep the ancient art of navigation alive.
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Pete Turner is a serving Officer in the Merchant Navy and the author of Maritime Training Online, a service providing the tools to become a Yachtmaster or Officer of the Watch. Read interesting articles, learn the COLREGs and find the best resources out there for navigation and seamanship.
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