Category : Reconstruction Engineering

The Need for Speed: Obtaining Speed From Video


James R. Schmidt, Jr., BSME, Collision Reconstruction Engineering Analyst

You guessed it! If Jim Schmidt is writing something, it must be regarding speed from video! That’s because I’m passionate about what I do! They don’t call me “Captain Video” for nothing.

A new year. A new dash cam. A routine drive home in the evening. One thing leads to another, pushpins were plotted, speed was calculated, and wouldn’t you know it … the same results! Perfection!

Pushpins were plotted for 59 seconds and 0.6 miles of travel. A speed versus time profile was generated from this plotting, and a comparison was made with the GPS speeds shown on the dash cam display. Assuming for this example the GPS speed display to be the actual speed of the vehicle (which is a reasonable assumption for normal driving with gradual speed variations), the independently calculated speeds were within 2 mph of actual over this entire time and distance. Additional pushpins could be plotted to refine this even further.

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