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From: "Robert I. Eachus" <rieachus@attbi.com>
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Subject: Re: float with 24-bit resolution
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Mark Johnson wrote:

> and we have to take that information plus the current location to
> generate a new location at the iteration rate of the model (say 30 Hz).
> The instructor is dealing with terms such as speed, bearing, and changes
> in those values while the software inside must generate X / Y position
> and do the appropriate conversions.

Right, my only point was that since the LSB difference in distances was 
small in any one time interval, errors would build up if you did:

for t in 1..n loop -- t in milliseconds
   X := X + Vx;
   Y := Y + Vy;
end loop;

instead of:

for t in 1..n loop
   X := X0 + t*Vx;
   Y := Y0 + t*Vy;
end loop;

(Of course, you are actually doing this for a set of tracks and looking 
for matches.)  I actually had to explain why the first formulation was 
not "more efficient."  (Or maybe it was more efficient, just wrong.  My 
attitude has always been that I don't care how fast you can calculate a 
wrong answer.)

-- 
                                            Robert I. Eachus

"As far as I'm concerned, war always means failure." -- Jacques Chirac, 
President of France
"As far as France is concerned, you're right." -- Rush Limbaugh