One of the Coastal Skipper candidates muttered something about GPS satellites being in geosynchronous orbits. Another muttered something in reply about them being confined to equatorial orbits.
This arose from the realization that the variation of a magnetic compass would increase dramatically as one approached the Poles. Unless, of course, one approached along a meridian which passed through the magnetic poles. Even so, the dip of a magnetic compass close to the poles would make it very inaccurate.
This led to a discussion that the use of Global Navigation Satellite Systems would be a better way to navigate close to the Poles (or indeed, anywhere else!).
The LG (in this context, a Lazy Sailor) was reminded of the time when he attended a five-day Astronavigation class which showed him that for the price of a decent sextant he could buy between 5 and 10 GPS instruments and that for the annual cost of tables he could buy all the batteries those instruments would ever need.
GNSS satellites are, of course, in geosynchronous orbits: they pass over the same spot on the surface once every day or once every half day. To do this they orbit at a precisely predetermined height at a predetermined speed. Each has a different orbital angle to the Equator so that a constellation of satellites covers most of the Earth's surface most of the time.
Because the satellites are moving with respect to the receiving instrument the latter must constantly search for other, more appropriately positioned, satellites.
By contrast, communications satellites are placed in geostationary orbits: they 'hover' above the same point on the surface all the time so that directional antennae (TV dishes!) can remain fixed pointing in one direction. These satellites orbit at the same speed that the Earth rotates, and they do so above the Equator.
The LS has always been an advocate for paper charts.
Yes, they get damp in the well of a small boat, especially a dinghy, but they can be enclosed in a waterproof case.
On a recent visit to Imray's offices Amy showed him their new-ish electronic charts on an iPad, and they were a revelation. They were, in appearance, scanned copies of the paper charts. No more disappearing detail that is so annoying with vector charts. Straightforward zoom by 'pinching' and tapping in the classic iPad way. And when you need the detail charts, simply zoom in to the detail charts.
The LS has always sailed away from teaching electronic navigation. He's used the old mantra "better to practice with the machine on the boat", which doesn't convince even he.
But now he has something sensible to teach.
As soon as he can persuade his iPad to communicate with his monitor and projector he'll use Imray Navigator.
He might even use it on the boat.
