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# how i foundout my car speed while sitting on the car

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#### drbizzarow

hi 2 all
can anybody help me find car speed withhout using its speedo meter...
i know it can be done by ultrasonic speed finder but i want to know the speed of a car when im sitting on it not out side the car any matter wil be very helpful to me

well seems your doing something adventurous...well what comes into my mind is mount a camera in front of the speedometer and have the screen on your lap outside the car...
Do tell us what are you up to...

Best Regards

Maybe an anemometer will help. But if there is a wind outside you have to correct the value you meassure.

Or a pressure meter. You have to convert the pressure to speed.

By using a GPS in your hand you can get the speed from the GPS.

A Gyrometer?

The distance between 2 lampposts is 50 meters. shorter in a built up area. time yourself between these 2 points and speed = distance divided by time

Use accelerometers:

V(t)=V0+a*t

a - acceleration (+ or -)
t - time
V0 - starting velocity (=0 at the begining)

You can measure distance too:

$S=V_0*t+\frac{a*t^2}{2}$

A beginner's guide to accelerometers

thx to all friends who guide me .......
im trying instal something in my car if someone drvie my car more the my set speed it start alarming etc

binu_ji & Pavel_S
..... im also thinking these to implement thse 2 idea ( GPS or Acelerometer). i think it will help to solove my problem. any comments on this idea wil be guide me more.
thx 2 all

barrybear said:
The distance between 2 lampposts is 50 meters. shorter in a built up area. time yourself between these 2 points and speed = distance divided by time

Is that distance standardized all over the world??

If not, where can I find such information for certain city or country??

drbizzarow said:
thx to all friends who guide me .......
im trying instal something in my car if someone drvie my car more the my set speed it start alarming etc

binu_ji & Pavel_S
..... im also thinking these to implement thse 2 idea ( GPS or Acelerometer). i think it will help to solove my problem. any comments on this idea wil be guide me more.
thx 2 all
Some advanced GPS got similiar function for speed limit.
There is another way to do it yourself a gauge with speed limit function. This will depends what communication protocol your car has. Most of new vehicle after 1996 got OBD on board, such as K line, J1850, CAN etc. You will need more info.

The distance between 2 lampposts is 50 meters. shorter in a built up area. time yourself between these 2 points and speed = distance divided by time
I am not shure about anywhere else but in England if you are in a built up area then the lamposts are closer together than if you are driving in a 40mile an hour area. Next time you are out see if this is correct.

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