[Wylug-discuss] Re: [Wylug-announce] WYLUG Social and micro-mapping

[Dave Fisher]

On Fri, Jun 20, 2008 at 08:50:22PM +0100, Roy Mac wrote:
> Keep in mind that at 54 degrees north, the GPS satellites are largely towards the southern sky.  There will be times where they are straight overhead or slightly to the northeast and northwest depending on your longitude.  These satellites will never be to the north from this latitude.  Therefore, it will be helpful to avoid blockage from southern sky.  I am not sure how much blockage the human body will add.  It might be good to try some experiments ahead of time to determine how much your body blocks the signals.  These satellites are in 12 hour orbits, so it would be good to try it several times throughout the day as the geometries are constantly changing.

Can you explain that in a little more detail?

How is it possible for the satellites ever to appear to our North East
or North West, and never to our North?

I can understand why geo-stationary orbits might always put them on an
arc to our South, but that would prevent them ever appearing to NE or
NW.

If they are not geostationary, I imagine they could have polar orbits
which were specifically designed to avoid the UK, but that would make
them somewhat less useful for our purposes here.

What am I missing?

And why have several GPS receivers which I've used in the past, *seemed*
to indicate that one or more of the locked satellites was actually
positioned to our North?

Dave