WAYPOINT - Drawing parallels between air and sea navigation

01 Oct 2012 The Navigator

Dr Andy Norris, an active Fellow of The Nautical Institute and the Royal Institute of Navigation, looks at marine navigation in the broader world of navigational practice and technology

The airline industry is often mentioned when marine navigation is under scrutiny. I was recently fortunate to have had a long discussion with Paul Hickley: a Fellow of the RIN and former senior instructor for airline pilots. Although fundamental navigational principles apply equally to both sectors, it is remarkable how different the detailed practice of navigation can be in each. Perhaps surprisingly, however, as technology evolves further, these differences could well become less marked.

Compare and contrast
An aircraft’s onboard flight management system (FMS) automates much of the in-flight navigation. In addition, the flight plan is often determined by a specialist ‘professional dispatcher’, although pilots are trained to be able to do this themselves.
In particular, pilots enter information relevant to the specific flight, such as loading weights — including fuel — which can significantly change the flight characteristics of the aircraft. During flight, the FMS determines the aircraft’s position and the accuracy of that position and alerts the pilot to any potential problems.

OOWs… will remain navigating officers, not monitoring officers

While the most obvious difference between air and sea navigation is the importance of altitude in aviation, threedimensional navigation remains important on a ship because of (charted) underwater hazards and low structures, such as bridges. In particular, the tidal height is a highly important aspect of some coastal navigation. In common with aircraft, the loading of the vessel must be controlled so that it remains stable under all conditions and the safe under-keel clearance is always known.
Currently, sea-going vessels do not have mandatorily carried equipment, or anything that reliably detects non-charted surface hazards like floating debris or large endangered species, such as whales. This therefore needs constant visual awareness and the correct resultant action by the navigating officer.

What’s next for navigation?
In the future there will be greater emphasis on the use of defined seaways and even shore-based instructions for maintaining a passage within the seaway; much like current airways. This is likely to be one consequence of IMO’s eNavigation programme. Ironically, in the air there will be some move away from airways, mainly to give more airspace, as many current airways are getting highly congested. This will still be tightly regulated but with a lot of automation.
Inevitably, there will be more automated navigation on ships too, again as a result of eNavigation, but it will be many years before OOWs are allowed to concentrate on tasks that are not navigationally centred. They will remain, for the foreseeable future, navigating officers, not ‘monitoring navigators’.

The use of the third dimension – altitude – is the most obvious difference.
Naturally, this has led to particular navigational practices that enable the efficient use of airspace with complete safety.

Increasingly, airline pilots do not see themselves as navigators. They use the FMS as a navigational tool: it is reliable and very safe.
In an emergency away from ocean waters they would depend on air traffic controllers to guide them to safety. The airline pilot can be seen as a ‘monitoring navigator’.

Airborne navigational errors are much more likely to lead to significant loss of life. Pilots must follow pre-defined airways with closely governed and monitored altitude and airspeed.
They have little choice on how to get from the destination to the arrival airport.

Depth and air draft issues also involve essential three-dimensional thinking, but this is very different from aircraft navigation.

At sea, bridge officers spend their watches primarily as navigators. The Officer of the Watch (OOW) must continuously assess the positional accuracy of the vessel, based on Global Navigation Satellite Systems (GNSS) such as GPS, as well as visual, radar and charted information.

If GNSS fails or becomes inaccurate, the OOW has to maintain his or her best estimate of position, including using dead reckoning and estimated position techniques. Most ships do not have the equivalent of an FMS, although an Integrated Navigation System (INS) does have some of its functionality.

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