The Stationary Brick Wall That Is Moving At 58 MPH
from the pretty-fast-for-a-wall dept
Bob Dole writes "Cameras never lie, right? Well, if they don't then someone needs to explain how brick walls can move at 58 MPH and stationary cars can be clocked at 4 MPH. A British laser expert explains that if a laser speed gun operator's hand slips while measuring speed, it can add (or subtract) significantly to the speed measurement. The accuracy of speed cameras has long been an issue in Europe and Australia. Now there's some science to back up the skepticism." Reminds me of the old joke that people say whenever they get into an accident with stationary objects: "it hit me." Well, if a stationary wall can go 58 MPH, I guess it can jump out and hit a car as well...
Thank you for reading this Techdirt post. With so many things competing for everyone’s attention these days, we really appreciate you giving us your time. We work hard every day to put quality content out there for our community.
Techdirt is one of the few remaining truly independent media outlets. We do not have a giant corporation behind us, and we rely heavily on our community to support us, in an age when advertisers are increasingly uninterested in sponsoring small, independent sites — especially a site like ours that is unwilling to pull punches in its reporting and analysis.
While other websites have resorted to paywalls, registration requirements, and increasingly annoying/intrusive advertising, we have always kept Techdirt open and available to anyone. But in order to continue doing so, we need your support. We offer a variety of ways for our readers to support us, from direct donations to special subscriptions and cool merchandise — and every little bit helps. Thank you.
–The Techdirt Team
Reader Comments
Subscribe: RSS
View by: Time | Thread
No Subject Given
[ link to this | view in chronology ]
Re: No Subject Given
Pull the other one, it hath bells on...
[ link to this | view in chronology ]
Re: No Subject Given
[ link to this | view in chronology ]
Re: Re: No Subject Given
Also, RADAR, being a high frequency radio wave, operates at the speed of light. The "calculation" is completed almost instantaneously. RADAR is not affected by the "vibration" of the mount....no matter what it is mounted on.
[ link to this | view in chronology ]
I read somewhere
[ link to this | view in chronology ]
Re: I read somewhere
[ link to this | view in chronology ]
[ link to this | view in chronology ]
As to the person saying that the movement of the device has no effect, Um, wrong.
Yes you are right that the measurement takes place very quickly, so quickly in fact that even a minuscule vibration in the proper direction will get added to the reading (or subtracted from if in that direction).
The problem stems from the fact that the system has no way to tell if the doppler change is coming from the movement of the object being watched or from the movement of the transceiver or laser/detector pair because there is no mechanism to detect movement of the device and compensate for it.
The faster and more sensitive the device the more prone to that sort of error it becomes. Averaging over many readings will help with the problem, but then the device would have to track the object for a longer period over a larger distance. That would usually work Ok for a Cop but it's not possible for a mounted camera the way they are built now.
[ link to this | view in chronology ]