Re: Pulsar Nav accuracy

Hello Roger,
  See, I'm getting confused myself...

>Let's see if I can  work my way through this.
>
>1.  I know the absolute locations of 3 pulsars (A B C).
>
>2.  Knowing two (A B) and their angles to my ship I know my
>    location on the surface of circle.
>
>3.  Pick another pair (B C).  I get another circle.
>
>4.  Pick the remaining pair (A C).  Yet another circle.
>
>5.  Intersect the three circles.  I now know where I
>    am.
>
>6.  For safety make it 6 pulsars and find the intersection.

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.