Re: Re: inertial systems

At 08:12 AM 5/31/2004 -0600, you wrote:
>John,
> > I just got a quote from KVH yesterday for their new 6DOF FOG IMU system --
> > $25,000 and 10-12 weeks delivery.  It looks like we will be sticking with
> > the Crossbow FOG for a while, although I am keeping my eyes out for either
> > a good integrated GPS / IMU that could reduce GPS position jumps, or a set
> > of gyros accurate enough to gyrocompass.
>
>You might want to check with some of the "low-cost ELV" companies.  I know
>that at least Microcosm and Aeroastro have both developed fairly low-cost
>IMU/GPS guidance packages that are supposedly good enough to fly an ELV all
>the way to orbit.  In at least Microcosm's case, I know that they supposedly
>cost less than $30k.  That's a heck of a lot for ameteurs, but might be
>within

These are almost certainly basically what we have -- a FOG based IMU and a 
separate GPS that outputs position.  Our current system should also also be 
capable of guiding a vehicle to orbit.  There is a tighter level of 
integration that is possible if the core GPS resolving algorithm also has 
access to inertial data as it weights the values from the various 
satellites.  This can get rid of the occasional discrete steps in position 
that GPS systems give as they transition from satellite to satellite.  A 
few meters isn't relevant for an orbital vehicle, but it matters for 
precision landing and maneuvering.

Just using differential GPS will probably be a lot easier.

John Carmack