I was avoiding this thread, but I've changed my mind. Darren has hit a
couple of points square on the head and there is another couple well worth
considering.
First, _any_ accelerometer system can only know acceleration (yeah, well
duh). What that leaves out is _displacement_ in the x-y plane created at
constant acceleration, otherwise known as drifting (never happens, right?).
Second, neither a _single_point_ accelerometer, nor a GPS system can tell
anything about yaw (ok, we never understeer or oversteer). Third, while
Byron has incorporated a roll constant for steady state correction, and well
done, the correction is entirely different under, shock absorber damped,
fast transitions than in sweepers. Admittedly, this is probably the
smallest factor of the three, but it would take some serious chassis
dynamics modeling to get that one right.
As an "early adopter" of GEEZ! I think the best feature of the software is
the various flavors of utilization. If the map is close enough to tell me
which corner I was at when I screwed up, that's what I find important. The
fact that the entrance is 20 degrees off from reality doesn't bother me a
whole lot.
If you want a course mapper that is accurate to auto-x apex standards (say 2
to 4 inches if your in third place) and can gather data at speed, on course,
you can't get there from here. From my investigations, one of the best
cost/performance ways to improve the situation would be to have two
accelerometer systems at a measured distance (x,y,z) at both ends of the
car, but his still doesn't get you all the way there.
Just my two bytes worth,
Brent DeWitt
-----Original Message-----
From: owner-geez@autox.team.net [mailto:owner-geez@autox.team.net]On
Behalf Of Darren Madams
Sent: Monday, March 25, 2002 5:37 PM
To: Byron Short
Cc: edcavalier@usa.net; geez@autox.team.net
Subject: Re: Extreme GEEZ opinions?
I think it's fair to set the expectation that you're not going
to get a picture that is unmistakebly the course you just drove
simply by loading the data.
Not Geez' fault, but a consideration if you're buying the
product for the mapping feature (i.e. trying to see where to
brake or which line to take). That info can of course generally
be derived from the data, but several people I know don't want
to analyze data, they just want to see an overlap view of the
different lines they took (kind of like the ghost mode in Gran
Turismo). I don't believe GPS is that accurate yet (espeically
in this price range), but maybe sometime in the future. I would
still like to see what Byron could do with Geez data combined
with a wheelspeed sensor.
--Darren
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