- Joined
- Oct 22, 2006
- Messages
- 400
- Trophies
- 0
- Age
- 40
- Location
- Grand Rapids, MI, USA
- Website
- Visit site
- XP
- 313
- Country
This is for people who either a) have an inside track of how police equipment works; or b) have an engineering/physics/whatever background and understand what's possible.
I understand how radar speed guns work -- the doppler effect, got it. I understand how laser speed guns work, and why they are incredibly accurate. I got it. Here's my question:
If a cop is driving toward you, can he 'accurately' tag your speed??
I was recently pulled over by a cop who was driving towards me. I came over a hill, going 60mph-ish. He made u-turn behind me and pulled me over. He asked me how fast I was going and I said "Sixty." He said I was going 67 (I might have been, coming over the top of the hill, but I was on my brakes slowing back down). Besides, it was apparently a 55mph zone. He wrote me a ticket for 5 over.
Anyhow, can he get my speed when he's driving towards me?
My science/match background says "No way." You have to take into account direction, the vector of the oncoming object, to get it's speed accurately. You can just say "I'm going 50mph, and it's closing in on my at Xmph, therefore it's going this fast." Because if I was angled away from him at a 45 degree angle, that speed would be different. Yeah my car would be closer to him, but it would reflect a slower speed (if I did my math right). Either way, it's still a different speed depending on the angles of the cars.
I'm tempted to challenge the ticket. Can he tag me like that? I did some Google searching but only found information on how radar/laser speed guns work ...
I understand how radar speed guns work -- the doppler effect, got it. I understand how laser speed guns work, and why they are incredibly accurate. I got it. Here's my question:
If a cop is driving toward you, can he 'accurately' tag your speed??
I was recently pulled over by a cop who was driving towards me. I came over a hill, going 60mph-ish. He made u-turn behind me and pulled me over. He asked me how fast I was going and I said "Sixty." He said I was going 67 (I might have been, coming over the top of the hill, but I was on my brakes slowing back down). Besides, it was apparently a 55mph zone. He wrote me a ticket for 5 over.
Anyhow, can he get my speed when he's driving towards me?
My science/match background says "No way." You have to take into account direction, the vector of the oncoming object, to get it's speed accurately. You can just say "I'm going 50mph, and it's closing in on my at Xmph, therefore it's going this fast." Because if I was angled away from him at a 45 degree angle, that speed would be different. Yeah my car would be closer to him, but it would reflect a slower speed (if I did my math right). Either way, it's still a different speed depending on the angles of the cars.
I'm tempted to challenge the ticket. Can he tag me like that? I did some Google searching but only found information on how radar/laser speed guns work ...