Calculating Speed on Video: Understanding How to Determine an Object's Velocity

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Discussion Overview

The discussion centers around calculating the speed of an object as captured in a video, specifically in the context of a car accident. Participants explore methods to estimate velocity despite challenges such as choppy video footage and the absence of standard distance/time calculations.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant seeks guidance on calculating speed from video footage, noting the limitations posed by the video quality and the context of a car accident.
  • Another participant suggests that knowing the frame rate and the length of the car can allow for an estimation of speed.
  • A further contribution indicates that if the video has a timestamp or constant frame rate, speed can be calculated by measuring the distance traveled by the car between frames and dividing it by the time interval.
  • Concerns are raised about the police and insurance company stating that proving the speed is impossible, prompting questions about their reasoning.
  • One participant speculates that the reluctance to calculate speed may stem from a preference to settle claims easily.
  • The original poster expresses motivation to pursue the calculation, sharing personal insights about the accident and their own vehicle's performance in relation to speed estimates.

Areas of Agreement / Disagreement

Participants express differing views on the feasibility of calculating speed from video footage. While some propose methods for estimation, others question the practicality and willingness of authorities to engage in such calculations.

Contextual Notes

The discussion includes assumptions about the availability of video frame rates and the accuracy of distance measurements, which may not be universally applicable. There are also unresolved questions regarding the reliability of the methods proposed.

LrS_IN
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Can someone explain to me how to calculate the speed of an object on a video.

I was involved in a car accident last week that was captured on my office security camera. The car that hit me is perpendicular in the film. The video is choppy, so real time is not possible, therefore I've not been able to use the standard distance/time. The police and insurance company have told me there is no way to prove the speed at which the car was traveling. I don't remember much from physics class (long time ago) but know there has to be a way.
 
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LrS_IN said:
Can someone explain to me how to calculate the speed of an object on a video.

I was involved in a car accident last week that was captured on my office security camera. The car that hit me is perpendicular in the film. The video is choppy, so real time is not possible, therefore I've not been able to use the standard distance/time. The police and insurance company have told me there is no way to prove the speed at which the car was traveling. I don't remember much from physics class (long time ago) but know there has to be a way.

You just need the frame rate of the video, and you can estimate the distance by knowing the length of the car.
 
If the video has a timestamp with milliseconds or hundredths of seconds or a constant framerate, you can calculate the speed with enough accuracy. Estimate the distance of a specific point on the car between two frames and divide it by the time between the frames you are comparing. Of course you would have to convert the measurement from feet (or meters) per second to miles (or kilos) per hour.
 
LrS_IN said:
The police and insurance company have told me there is no way to prove the speed at which the car was traveling.
Why? This is what they do.
 
DaveC426913 said:
Why? This is what they do.

Because it's easier & cheaper to just pay off the claims.
 
Thank you for responding. I know there are much more interesting threads on this forum. It's been very informative looking around this board, it makes me want to learn more so I can understand them.

I will try to figure out at what rate the video recorded and look up the length of the other person's SVU.

My car was 3 months old, with less than 5 K miles on it. My state is no fault unless one of the vehicles is breaking the law. I'm motivated for several reasons: one because everyone keeps saying the calculation can't be done (do I hear a challenge ?). Another, I estimate the other car was going at least 60 in a 45 and was less than 4 seconds from a 25 mph school zone. I tried to accelerate from 25 to 45 in a fuel injected 6 cylinder car today in 4 seconds and made it to 30 max.
 

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