On the Topic

In view of three satellite navigation systems, why do we still need astronavigation? Can a sextant on board increase safety at all, and is the phrase „good seamanship“ still an argument for an astronavigation backup?

Most skippers nowadays sail without an astronavigation backup and simply trust the technology of their satellite navigation. Why? Because astronavigation, as it is supposed to be used today in the age of artificial intelligence for emergencies, is a real imposition. It also, as many see it, no longer has any practical use. However, anyone who wants to obtain an ocean navigation licence cannot avoid astronavigation. Those who are not comfortable with self-study may have to pay for an expensive course. Apart from broadening your general knowledge, which is not a disadvantage, the main purpose of the course is to pass the upcoming exam. A few weeks later, everything is forgotten anyway and all the hoped-for benefits are gone.

It is not wrong to bring „good seamanship“ into play in navigation, which says that for every system there must always be a back-up system on board. But as honourable as the high art of navigation of the last generation of seafarers before the satellite age was, it is completely unsuitable for use as an emergency back-up in our time, because it no longer fulfils its purpose. Hardly anyone will want to get used to working with the tools of past generations.

A satellite navigation failure is not impossible. Satellite signals can be disrupted or on-board systems can fail. Both have happened before and an unavailability of satellite navigation would immediately send a boat at sea back to the 19th century. The sea is not a safe place.

What is needed is an astronavigation system that can be used ad hoc by everyone. It must be simple, self-explanatory and usable without knowledge in mathematics or astronomy. It must also be affordable. Procedures that could be used to build such navigation devices have been known since the 18th century and go back to the work of famous mathematicians such as Leonhard Euler or Carl Friedrich Gauss. However, these so-called analytical methods, which simply calculate a location at sea from only two measured celestial altitudes, could not be used at that time because there were no calculating machines.

The boom of sea power and sea trade in the 19th century urgently required solutions and these were not provided by scholars at the time, but arose directly in practice. It was the merchant captain Thomas H. Sumner and the frigate captain Marqc Saint Hilaire who solved the problems of astronomical navigation with their work. They invented graphic astronavigation, which subsequently established itself as the global standard and quickly displaced the exact analytical methods. Graphic navigation was only replaced by satellite navigation at the very end of the 20th century.

Many books have been written about astronavigation and articles have been published in specialist journals, and there are also numerous articles on the internet. In addition, many computer programmes and apps have become known that are supposed to make navigating with celestial bodies easier. But almost everything revolves exclusively around the Saint Hilaire intercept procedure. Those who book a course – which of course still exist – are not offered anything else. However, this graphical approximation method no longer fits into our time, where digitalisation and AI are unstoppable. Should astronavigation therefore disappear altogether? However, that would be going too far, because it is and remains the last lifeline. It is much more important to make astronavigation usable for our time, and strangely enough, this is only possible with the very old procedures that disappeared from memory 150 years ago. Little or nothing is known about these procedures any more. That is why it is time to present them on a web page like this one. Because graphic astronavigation has also become known as modern astronavigation, this web page has been given the title Postmodern Astronavigation.