NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: accuracy of automatic celestial navigation
From: George Huxtable
Date: 2002 Dec 9, 08:15 +0000
From: George Huxtable
Date: 2002 Dec 9, 08:15 +0000
Thank you, Paul Hirose, for another interesting insight into precise astro-navigation. It seems to me that the magic of the system must lie in the nature of the coupling between the inertial navigation and the astronavigation, as Paul explains. The inertial system would slowly drift off, the astro will stabilise it against that drift: but the astro system must require the short-term stability of the inertial to stabilise its reference platform before it can work. So I don't see much prospect of that sort of technology being applicable to us in our small boats until the costs of inertial nav systems are brought down to affordable levels. And on a rough sea-surface, the disturbing accelerations are orders of magnitude greater than a high-altitude aircraft has to contend with. It raises yet another question. If indeed an accuracy of 15 to 30 meters was claimed for the system as a whole, how was that error measured and tested? Precise position in an airbase parking bay is one thing: in-flight precision in the real world is another. In the days before GPS, how could the instaneous position in flight be independently determined sufficiently accurately, for testing purposes? Is Loran accurate enough, and fast-responding enough? The aircraft will presumably pass through 15 metres in less than 30 milliseconds, so it's a demanding requirement. Fascinating stuff, but it makes the heart sink a little to observe so much ingenuity being applied to weapons of war. George Huxtable. ------------------------------ george@huxtable.u-net.com George Huxtable, 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK. Tel. 01865 820222 or (int.) +44 1865 820222. ------------------------------