Re: Pulsar Nav accuracy

----- Original Message -----
From: <hal@buffnet.net>
To: <gzg-l@csua.berkeley.edu>
Sent: Wednesday, February 27, 2002 5:10 AM
Subject: Re: Pulsar Nav accuracy

> Hello Roger,
>   See, I'm getting confused myself...
> Lets say for the sake of argument, that I attempt to take a bearing on
> Pulsar A.  I get that bearing.  At the same time, I have someone else,
or
> the computer take readings automatically) that gets the bearing on
Pulsar
> B.  For this "exercise" I have the bearings on both known Pulsars,
along
> with their *known* 3d co-ordinates.  From those two known
co-ordinates, I
> should be able to compute the third co-ordinate (my location).  This
is
why
> I am confused as to why it should require more than *two* pulsars... 
Mind
> you, I'm not saying "exact" co-ordinates down to precision values, but
> general ball park at least.

Taking a bearing means that you take the angle between that point and a
standard direction (e.g.North). Under the assumptions we have been
discussing, you don't know anything about directions and very little
about
location after coming out of a jump.

So you can't "take a bearing". What you can do is measure the angle
between
the line-of-sights to the 2 pulsars. With the distance between the two
pulsars you can define a triangle joining you with the pulsars and know
your
distances to the pulsars. Works on paper - I mean not only "in theory"
but
with a scale drawing on a piece of paper. But that's 2-dimensional

Now the problem in 3d: Draw the triangle. Fold the paper along the line
joining the pulsars. You can fold the paper up or down any angle and the
shape of the triangle stays the same. Your measurements have not given
you
the angle in 3d. That means you know you are on a very big circle in
space,
but not where on that circle.

Greetings