AVR speedometer.

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Y'all know this is a 10 year old resurrected don't you?

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Yes - see #44 ...

 

EDIT

 

Perhaps all the banter from #36 on should be split to "Off-topic" ... 

Last Edited: Mon. Nov 6, 2017 - 08:57 AM
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Resolution to one mile per hour, compares well with my new cars.

GPS gets around errors related to tire diameter variation due to, inflation, wear, loading, and speed. Also, there is tire slip when wet or rough terrain.

It all starts with a mental vision.

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Resolution != Accuracy

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Surely a GPS speedo just measures localized ds/dt? As long as the difference between x1, y1 and x2, y2 used to determine ds are not a huge distance apart then any error in their true location is immaterial isn't it? The distance measurement itself should be fairly accurate shouldn't it?

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So long as the position error is consistent...

 

 

 

 

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Surely a GPS speedo just measures localized ds/dt?

Conceptually, Yes.

 

In practice, probably not.

 

Although the GPS uses trilateralization to determine location, at low speeds and therefore short distances traveled between successive measurements, the error of the delta distance, and therefore heading and velocity become significant.

 

Many GPS units, I think, actually use the Doppler shift in the received signal to measure velocity.

 

JC

  

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There are GPS speedometers on the market. Custom vehicles like street rods use them for ease of installation, and lack of calibration requirements when changing gear ratios, tire diameters.

http://www.speedhut.com/gauges/Speedometers/GPS-Speedometers/?catid=f8|f37

It all starts with a mental vision.

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The GPS speed on my phone matches quite will with the speedo on my car, and with the cycle computer on my wife's bike.  Within 1 km/h.

"Experience is what enables you to recognise a mistake the second time you make it."

"Good judgement comes from experience.  Experience comes from bad judgement."

"When you hear hoofbeats, think horses, not unicorns."

"Fast.  Cheap.  Good.  Pick two."

"Read a lot.  Write a lot."

"We see a lot of arses on handlebars around here." - [J Ekdahl]

 

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"Many GPS units, I think, actually use the Doppler shift in the received signal to measure velocity."

 

I did not know that. Thanks.

Quebracho seems to be the hardest wood.

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"Experience is what enables you to recognise a mistake the second time you make it."

"Good judgement comes from experience.  Experience comes from bad judgement."

"When you hear hoofbeats, think horses, not unicorns."

"Fast.  Cheap.  Good.  Pick two."

"Read a lot.  Write a lot."

"We see a lot of arses on handlebars around here." - [J Ekdahl]

 

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