NavList:

Dear List Members,

I've just finished driving south from Darwin to Adelaide right through Central Australia, after having traveled up there on the new railway line from Alice Springs to Darwin on the Ghan, the longest North / South train journey in the world.  I stopped off at Woomera, in South Australia, which used to be the centre for guided missile and rocket testing in Australia.  The Woomera Prohibited Area is 127,000 square kilometres, or 12.7 million hectares, larger than many countries.

In the Woomera township they have mounted an exhibition devoted to Len Beadell, who has been described as "The Last Australian Explorer" because of his lifetime of work surveying, mapping and creating access to a vast portion of the Australian Outback. In 1947, he was tasked by the Australian government to locate and survey the site for a rocket testing range in northern South Australia stretching across West Australia almost to the Indian Ocean. The town that was the base for the range was later named Woomera. This he tackled with enthusiasm, energy and unfailing good humour.

As a surveyor Len was responsible for the initial town survey and launch sites and in the years to follow he led a gang of roadmakers to create over 6,500 kilometres of access roads for scientific observers of various weapons tests. The best known of these roads is The Gunbarrel Highway which runs from the Stuart Highway west to Carnegie Station, a distance of 1500 kilometres.  The atomic bomb test sites at Emu and Maralinga in South Australia were also located and laid out by Len Beadell during the cold war years of the 1950's.

In several of his books (which are delightful reads) he describes performing astronomical observations, and the resulting calculations, as giving him an "astrofix".  He used a theodolite, radio time signals and books of tables to help with the arithmetic (this was well before electronic calculators).  A compass was used for basic navigation, but positions were fixed astronomically.

My questions to List members are as follows:

1. Do the leveling devices on theodolites provide a better "horizon" than an artificial horizon used with sextants?
2. When did theodolites become generally accepted for land based exploring, and replace sextants and artificial horizons?
3. Why didn't more early explorers use theodolites for astronomical observations and navigation?  I understand that Thomas Jefferson used a theodolite in his own surveying practice, but did he equip the Lewis and Clark expeditions with one?
4. What is the basis of the calculations to derive an "astrofix"?  Are they similar to the "Line of Position" methods used in celestial navigation?

A question to Kieran Kelly, whose two books on Gregory and the Tanami Desert I really enjoyed:  why did you use a sextant and artificial horizon when crossing the Tanami and not a theodolite?  Was it a matter of historical accuracy in replicating Gregory's observation methods, or just a matter of weight and convenience when packing camels?  Did Gregory use a theodolite on any of his Australian exploring expeditions?

I realise these questions are more related to surveying than navigation, so I hope I haven't crossed the line too badly.  As I understand it the purpose of the list is "discussion of all methods and techniques of the art of non-electronic navigation ".

I enjoy the conversations on this list immensely, and really appreciate all the contributions made by members.

Regards to all,

Greg Gilbert

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