Why Gamin 18X is too precise?

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Why Gamin 18X is too precise?

solver90
I have a Gamin 18X to do some experiment with it in urban area

when i saw the manual (http://static.garmincdn.com/pumac/GPS_18x_Tech_Specs.pdf), this GPS has an accuracy in position of 5m in RMS, and an accuracy in velocity of 0.05m/s.

My question is: How can we have this accuracy in term of velocity? (additional sensor inside the receiver, other signal used,....).

Thanks
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Re: Why Gamin 18X is too precise?

Brian Wilson
GPS uses Doppler to measure velocity. See http://gpsinformation.net/main/gpsspeed.htm
 and especially the comment that Garmin really is probably accurate to .5 not .1 miles per hour (or roughly knots)

In the 18X spec sheet I see this

1.6.3.4 Accuracy
• GPS Standard Positioning Service (SPS) Position:
< 15 meters, 95% typical
Velocity: 0.1 knot RMS steady state
• WAAS
Position:< 3 meters, 95% typical
Velocity: 0.1 knot RMS steady state

Maybe you are reading the wrong section? I don't see any reference to .05 m / s

Also note that "RMS steady state" implles they are doing averaging.

Hope this helps


Brian



On Tue, Apr 7, 2015 at 1:31 AM, solver90 <[hidden email]> wrote:
I have a Gamin 18X to do some experiment with it in urban area

when i saw the manual
(http://static.garmincdn.com/pumac/GPS_18x_Tech_Specs.pdf), this GPS has an
accuracy in position of 5m in RMS, and an accuracy in velocity of 0.05m/s.

My question is: How can we have this accuracy in term of velocity?
(additional sensor inside the receiver, other signal used,....).

Thanks



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Re: Why Gamin 18X is too precise?

solver90
Thanks Brian

you are right, for the precision yes it's an average of 0.05 meters/second because 1knots = 0.514444444 m / s.

I had done some test, and even in severe environments, the results are surprising, good GPS with pseudoranges + Doppler observations.

Thanks