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Hi all,

I'd like to track the tracjectory of a rally car and would like to know the
level of accuracy I can get with GPS. Can anyone tell me how fast a fast GPS
receiver can update its position?

Cheers

Paul

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Sorry, only 1Hz.

Maybe the EU's new system will have a better rate, if it ever gets off the
groud.   (Which is doubtful.)

-Kevin

"Paul Winton" <p...@paric.co.nz> wrote in message
news:vx7Qa.4617$9...@news02.tsnz.net...
> Hi all,
>
> I'd like to track the tracjectory of a rally car and would like to know
the
> level of accuracy I can get with GPS. Can anyone tell me how fast a fast
GPS
> receiver can update its position?
>
> Cheers
>
> Paul
>
>

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"Paul Winton" <p...@paric.co.nz> ha scritto nel messaggio
news:vx7Qa.4617$9...@news02.tsnz.net...

> I'd like to track the tracjectory of a rally car and would
> like to know the
> level of accuracy I can get with GPS. Can anyone tell me
> how fast a fast GPS
> receiver can update its position?

I've seen models up to 20 Hz, they cost around 2-3000 $. I know there
are models at 50 Hz, but they cost a lot more.

Maybe there is something even better (military applications?), but
probably it costs more than the rally car. :)

-- 
Lorenzo

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On Sun, 13 Jul 2003 19:39:51 GMT, "Lorenzo Lutti"
<l...@DOHtiscalinet.it> wrote:

>"Paul Winton" <p...@paric.co.nz> ha scritto nel messaggio
>news:vx7Qa.4617$9...@news02.tsnz.net...
>
>> I'd like to track the tracjectory of a rally car and would
>> like to know the
>> level of accuracy I can get with GPS. Can anyone tell me
>> how fast a fast GPS
>> receiver can update its position?
>
>I've seen models up to 20 Hz, they cost around 2-3000 $. I know there
>are models at 50 Hz, but they cost a lot more.
>
>Maybe there is something even better (military applications?), but
>probably it costs more than the rally car. :)
>
>-- 
>Lorenzo

If it's for World Rally it could cost a LOT and not be more than the
cost of the car.  ;)

If GPS alone turns out to not be adequate then a GPS mated with an
Inertial Measurement Unit should be able to provide very, very
accurate trajectory measurement.  The IMU is essentially the primary
sensor but the GPS would provide updates to control drift in the
sensor.  Usually these inputs are used with a Kalman filter that
provides the position/trajectory estimates.


Eric Jacobsen
Minister of Algorithms, Intel Corp.
My opinions may not be Intel's opinions.
http://www.ericjacobsen.org

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Paul Winton wrote:
> Hi all,
> 
> I'd like to track the tracjectory of a rally car and would like to know the
> level of accuracy I can get with GPS. Can anyone tell me how fast a fast GPS
> receiver can update its position?
> 
> Cheers
> 
> Paul
> 
> 

The actual range measurement on which the position calculation is based,
is an instantaneous snapshot of the code tracking loops.

The theoretical limit is down to the integration time for the receiver,
typically 1-10ms. If you want high dynamics, you need to update faster.
For car racing, it's probably closer to 1ms.

Most comercial receivers output 1 position per second because it takes
some number crunching to compute the satellite positions and solve for
the receiver position. This is purely a matter of computing power.

Given a fast enough processor, 1000 positions per second is possible.
I was running an automotive receiver IC (60MHz,32bit MIPS processor)
at about 10 fixes per second, getting close to 100% CPU.

Apart from getting a manufacturer to customise a receiver for you,
Eric's suggestion to use dead reckoning techniques is probably best.
Especially if you bear in mind that very few GPS receivers can handle
the dynamics of a car race without getting inaccurate.

Kind regards,

Iwo

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