Celestial Navigation in the GPS age?

Considering the price of a useful sextant and the accuracy-of-position achievable with celestial navigation, compared to the price and accuracy of a receiver for the satellite-based Global Positioning System (GPS), it seems curious that the 'art of celestial navigation' is still in use in modern navigation.

A quality marine sextant suited for celestial navigation, will cost at least 500 Euro/Dollar. The expected accuracy of position under good weather conditions will be in the order of one nautical mile. A simple GPS receiver on the other hand, giving position data within 0.01 nautical miles of accuracy, today costs less than 200 Euro/Dollar.

So for less than half the price of a sextant, a GPS receiver will give an accuracy of position which is at least 100 times better than the accuracy achievable with a sextant and celestial navigation. Moreover, GPS receivers work under all weather conditions. Meaningful celestial observations on the other hand are only possible if the sky is clear enough so that the required celestial objects are visible and only if the sea is not too rough to allow for an accurate Altitude measurement.

The GPS itself, is a highly reliable navigation system and although initially intended for military purposes it is meanwhile intensely used for many civil navigational applications world wide. The fact that the GPS is maintained and controlled by the US Department of Defence shouldn't worry too much. In order to keep this controlling position, the DoD should in fact be interested in a broad range of civil applications, just to prevent a commercial break through of alternative and competing systems such as GLONASS (Russia), GALILEO (Europe) or COMPASS/BeiDou-2 (China).

Since the GPS satellite infrastructure itself (the "space" and "control" segments) is redundant and quite reliable, a second low-end GPS receiver that serves as backup system on board, is sufficient to obtain a very secure and cost effective 'real-time' navigation system that works under all weather conditions.


The situation today is that modern marine navigation systems such as radar and GPS receivers in combination with an electronic chart plotter, simply belong to the basic navigation equipment of any offshore sailing vessel.

So why still attending to celestial navigation?

The availability of highly accurate and reliable 'real-time' electronic instruments definitely has relegated celestial navigation to one of those romantic, but rather impractical 'arts of the sailor', just like sailing itself.

But although, celestial navigation is not essential to nautical navigation any more, it definitely gives some of us a sense of satisfaction and joy of keeping alive this knowledge that connects us with the universe and with a very special legacy and tradition from our navigator forefathers. Moreover, understanding celestial navigation and it's underlying combined knowledge of Astronomy, Geography and Mathematics, gives us a more profound perspective to the navigational problems faced and mastered by those great discoverers like Magelães, Tasman and Cook. Eventually, celestial navigation today can be seen in the same spirit of what Nathaniel Bowditch (1773 - 1838) wrote in his famous "practical navigator": "The science of navigation can be taught, but the art of navigation must be developed from experience".

Today, "Sailing" on small leisure yachts is more than just travelling from one port to another in a slow and rather uncomfortable way! Sailing in modern times, has become a way of experiencing and developing an 'art of life'. This kind of sailing stands for an intensified confrontation with the elements of nature - wind and water. It symbolizes a life on the sea reduced to the simplest basic needs. And it is associated with the adventure of exploring unknown regions of special beauty and the experience of relatedness with people of different cultures all over the world.

The 'art of celestial navigation' adds a kind of cosmological dimension to this way of life. It elevates navigation to a skill, which requires more than being able to read a position from a GPS display and plot it on a chart. The fascination about celestial navigation is indeed 'the finding' of one's position - anywhere on Earth - just by observing the sky and doing some calculations; using simple things such as a sextant, an Almanac and some pre-calculated tables. And for offshore sailing, the accuracy of this method is sufficiently high to safely 'navigate with the stars'.

Despite the availability of fully electronic navigation aids, from a seamanship point of view a profound competence in conventional piloting including celestial navigation still remains essential to marine navigation.