Re: Inertial Navigation ???

From:         inet@intellisys.net (brian whatcott)
Date:         13 Mar 2000 10:01:43 -0800
Organization: Teleport
References:   1
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In article <u0r9dkj89i.fsf@orville.dfrc.nasa.gov>, emcbride@wybron.com 
says...

>I am a consulting engineer in Colorado Springs with a client who wants
>to track a few objects using on-board accelerometers and gyroscopes
>that communicate with a central processor. The objects are confined to
>an area of roughly 25 meters square, and a height of no more than 5
>meters above ground.  It is necessary to know the location of each
>object within about 0.1 m, over a time period of a half hour or so.
>The objects can move at speeds up to 10 m/s, and can experience
>accelerations up to 2-3 g (20-30 m/s^2).  The objects can also rotate
>at angular velocieies up to a few rev/s. (10-15 rad/s).  The cost of
>the system cannot exceed something like $2,000 per object.

>....  Can anyone please either
>explain to me what's going on, or point me to a reference that will
>help me figure things out?

Let's see if I can explain.

A client decided on the basis of some experience he thought was
relevant that he would specify a navigation system used in world wide
operations in an agile close range scenario.

It didn't work, so you were called in to *make* his design decision
work.  

You might point out that INS drifts a mile each hour (or less if you
are lucky) unless it gets a mix from TACAN or GPS or whatever.

There are other systems more resistant to maneuver- a short range
equivalent to LORAN was SHORAN for example.  This pinged a tracked
object from several points - and the transit time and known
transmitter ordinates led to well defined fixes in real time.

In your case, the EM pulse transmission speed is so high at close
range you have problems measuring very short pulses.

So you could reasonably specify *acoustic* pingers on a selective call
basis and get a real time triangulation without breaking much of a
sweat, I would think.

You will *certainly* get a lot of opposition to this proposal.  It is
after all, cheaper, simpler and ..er.. better.

Brian Whatcott       Altus OK