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Speed calculation

 
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Stephane



登録日: 2008.10.12
記事: 92

記事日時: Sun May 22, 2011 5:08 pm    記事の件名: Speed calculation 引用付きで返信

Hi Sonotaco

How you compute the speed between each picture of video what is your formula?)

Thanks and best regards.

Stephane
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SonotaCo
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登録日: 2004.08.07
記事: 9387
所在地: 139.66E 35.65N

記事日時: Sun May 22, 2011 5:53 pm    記事の件名: Re: Speed calculation 引用付きで返信

Stephane wrote:
How you compute the speed between each picture of video what is your formula?)

It is not so simple.
Basically UFOOrbitV2 compute observed velocity from the length of the trajectory and duration time that were got from triangulation of multiple observation.
So it is the average speed under the constant speed assumption.
Geocentric velocity is got from observed velocity using Earth's self rotation speed and orbital velocity.

If you want to get the ground speed of each frame, then you should compute the geographical position of each frame using computed trajectory information.
It is not the function of UFOOrbit but its of FireBallInspector(not published).
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Stephane



登録日: 2008.10.12
記事: 92

記事日時: Sat May 28, 2011 5:00 am    記事の件名: 引用付きで返信

Hi Sonotaco,

Thanks for your answer.

Regards.

Stephane
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tgmeteor



登録日: 2017.02.08
記事: 2

記事日時: Thu Feb 09, 2017 2:40 am    記事の件名: 引用付きで返信

Hi Sonotaco and all,

I'm french observer. I have a question about geocentric velocity computation with UFOorbit. Is it possible to have 13.0 km/s for observed velocity and 6.4 km/s for géocentric velocity?
I thought the lower velocity for a meteor was 11,2 km/s.

"Geocentric velocity is got from observed velocity using Earth's self rotation speed and orbital velocity."
Ok, but, between vg and vo the only difference it's earth's self rotation speed, how it could be higher than 0.5km/s?

An other question vi is ever equal to vo? If I remember post or discussion, UFOorbit just calculate an average velocity for a meteor or a fireball, it couldn't really get initial velocity?.

Thanks in advance for your reply
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SonotaCo
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登録日: 2004.08.07
記事: 9387
所在地: 139.66E 35.65N

記事日時: Thu Feb 09, 2017 8:45 am    記事の件名: 引用付きで返信

Hi
tgmeteor wrote:
Is it possible to have 13.0 km/s for observed velocity and 6.4 km/s for géocentric velocity?
Yes.
tgmeteor wrote:
I thought the lower velocity for a meteor was 11,2 km/s
Almost Yes for Vo, but No for Vg.

tgmeteor wrote:
"Geocentric velocity is got from observed velocity using Earth's self rotation speed and orbital velocity."
This is too rough, ambiguous, or not correct, please forget.
It may be as blow...

The relative velocity between one ground station and the object: Observed velocity : Vo
Earth's self rotaion velocity at the observation point: Vr
Decelaration by the atmoschere: Vd
Observed velocity measured at infinite: Vi = Vo - Vr + Vd
Acceraration by the Earth's gravity: Va
Geocentric velociry: Vg = Vi - Va , means the relative velocity between the center of the Earth and and the object, assuming the Earth does not exist, is used for meteor orbit computation.
Earth's orbit velocity: Ve
Heliocentic velosity: Vh = Vg - Ve

Be aware all velocity should be computed as a three dimensional vector not a single value.
Va is so called Zenith attraction effect.
Vd is assumed as 0 on UFOOrbit,and even Vo is mueasured as the average velocity of luminous path in the atmosphere, it is because the the path is too short for measureing the decelaration of most of the meteors, and the decelaration of most meteors (except big fireballis) is very small..
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tgmeteor



登録日: 2017.02.08
記事: 2

記事日時: Fri Mar 10, 2017 5:55 pm    記事の件名: 引用付きで返信

Thank you very much for your reply Sonotaco

It's clear now for me.
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