Radar Gun

[monta]

Radio Shack now sells a cheap radar gun ($75)...

I overheard someone say "Looks like the Shark is doing 80mph in the slalom";
with a radar gun; we'd know . I announce frequently and I can imagine sitting in the trailer taking radar potshots at cars on the track and announcing them as part of the color commentary. It's not like we'd use it as a "required device", but having one available to compare speeds among drivers and cars would be interesting. I don't really know what the procedure is for suggesting such a thing so I thought I'd post it here.

Here's more info on the Radar Gun.
http://www.radioshack.com/product/index ... age=search



"The Bushnell Speedster Speed Gun uses digital technology and digital signal processing to provide accurate, real-time measurements up to +/-1 MPH. Use it to clock a baseball's speed from 90 feet away or a race car from 1500 feet away. Measure speeds from 10 MPH to 200 MPH."

-Monta

[techteg]

Monta, I'll admit that Myself and my codriver had a little fun messing with
you with one of those on the drive home from the Mercer County event earlier this year.

Remember all the mysterious full force blasts of Ka band coming from nowhere?

[drum3]

My car has a speedo,I always know how fast I'm going.

[ColinS]

Monta, I'll admit that Myself and my codriver had a little fun messing with
you with one of those on the drive home from the Mercer County event earlier this year.

Remember all the mysterious full force blasts of Ka band coming from nowhere?

[01:36 AM] mike: did I tell you what happpened on our drive back from mercer?
[01:36 AM] me: nope
[01:36 AM] mike: I co drove stephens car that day
[01:36 AM] mike: well, we are all driving home in a caravan
[01:36 AM] mike: im in stephens car
[01:37 AM] mike: matts in his rx7, rob in his crx
[01:37 AM] mike: and the mustang is driving by us
[01:37 AM] mike: I recently bought a radar gun and brought it with me
[01:37 AM] me: ROFL
[01:37 AM] me: I HATE THAT
[01:37 AM] me: so not funny
[01:37 AM] mike: so I turn it on and clock him
[01:37 AM] mike: he SLAMS on his brakes
[01:37 AM] me: hey, I run a radar detector
[01:38 AM] me: don't hate.
[01:38 AM] mike: but we were also going into a construction zone, so I wasnt sure
[01:38 AM] me: hahahhaha
[01:38 AM] mike: we get up next to him, and I see it in the corner of his windshield
[01:38 AM] mike: I could barely control my excitement....

[monta]

I was thinking it would be fun to light them up on the highway and see what brake lights came on.

A little further reading shows that they only work properly when the measured item is traveling (almost) directly towards or directly away from the gun. That would limit its usefulness in the trailer some.

Would you mind letting me use the gun at the next evet (assuming I get an announcing position)?

-Monta

[glenthompson]

Radar 101:

Doppler radar only measures the speed at which an object is approaching the radar. If it is on a parallel course, the speed measured is a fraction of the actual speed. The speed measured is equal to the cosine of the angle between the vehicle course and the line to the radar gun. At longer distances the angle is minimized as long as you're close to the vehicle course.

If you're straight on the the vehicle, the angle approaches 0 and the cosine of 0 is 1.0 so the speed is accurate. If the angle is 30 degrees, the speed shown is 87% of the actual speed. at 45 degrees it drops to 71%. Perpendicular to the course and it's 0% since the cosine of 90 is 0.

Standing at one of the worker stations at Danville and measuring towards the end of the slalom would have an angle of less than 10 degrees. That would put the speed shown at 98% of actual. At 60 MPH that's just under 59. Close enough.

[mpg9999]

I was thinking it would be fun to light them up on the highway and see what brake lights came on.

A little further reading shows that they only work properly when the measured item is traveling (almost) directly towards or directly away from the gun. That would limit its usefulness in the trailer some.

Would you mind letting me use the gun at the next evet (assuming I get an announcing position)?

-Monta

Sure, as long as you don't hit me with it for messing with you on that drive back from Mercer .

And yeah, as Glen has pointed out, its called cosin error. Not a big deal as long as the angle isnt to great. As an interesting side note, you can use cosin error to fight speeding tickets.

[DSPDA3]

As far as using a detector on the highway, I never was a fan. Why spend all that money for a good detector when they're illegal in VA? Put that money towards some race tires. Also, just drive the speed limit, and you never have to worry about it.

[Imprezzed]

As an interesting side note, you can use cosin error to fight speeding tickets.

Go for it, but it'd be a dumb thing to do...with the cosine error, the speed on the radar gun will always read LOWER than what you're actually doing. Also, a RADAR gun will always round the speed down. So if it's reading 57.9mph, it'll only show 57 on the display. The gun will always favor the motorist.

[mpg9999]

As an interesting side note, you can use cosin error to fight speeding tickets.

Go for it, but it'd be a dumb thing to do...with the cosine error, the speed on the radar gun will always read LOWER than what you're actually doing. Also, a RADAR gun will always round the speed down. So if it's reading 57.9mph, it'll only show 57 on the display. The gun will always favor the motorist.

Nope, it would be an extremely intelligent thing to do. The radar manuals always say that it favors the motorists, so they never pay attention to it, but it can be used cleverly to trap them, that is, if you know how to do it. It basically involves getting the officer to say he visual observed you speeding (they are supposed to do this, then "verify" it with a radar gun). You have to get them to testify how long it took them to visually estimate your speed. If you know when the car came into view, how long it took them to make that estimate, and how fast he claims you were traveling, how long it took the radar gun to lock on, then you can calculate exactly where the car was when the officer finished clocking you. Since they don't really take the time to visually estimate the speed, but they have to testify they did, when you do the calculations your car will end up being alot further along. If you have a sharp enough angle, then your car would have had to have been traveling significantly faster then what he said you were doing. Of course, he previously testified that you were traveling much slower then that newly calculated speed. Case dismissed. Not at all dumb if you're smart enough to know what your doing .

[Imprezzed]

Nope, it would be an extremely intelligent thing to do. The radar manuals always say that it favors the motorists, so they never pay attention to it, but it can be used cleverly to trap them, that is, if you know how to do it. It basically involves getting the officer to say he visual observed you speeding (they are supposed to do this, then "verify" it with a radar gun). You have to get them to testify how long it took them to visually estimate your speed. If you know when the car came into view, how long it took them to make that estimate, and how fast he claims you were traveling, how long it took the radar gun to lock on, then you can calculate exactly where the car was when the officer finished clocking you. Since they don't really take the time to visually estimate the speed, but they have to testify they did, when you do the calculations your car will end up being alot further along. If you have a sharp enough angle, then your car would have had to have been traveling significantly faster then what he said you were doing. Of course, he previously testified that you were traveling much slower then that newly calculated speed. Case dismissed. Not at all dumb if you're smart enough to know what your doing .

Good luck using that in court is all that I have to say. The judges know about the cosine effect as well. They don't have a lot of patience for people who use it as a defense that the radar reading was wrong. The only radar case that I've lost was because I didn't have the calibration sheet for the tuning fork I used.

Just want to say that once you get to use the radar systems that police use, you know what any time you got a speeding ticket, they got you good. Moving radar is very cool

[ColinS]

As far as using a detector on the highway, I never was a fan. Why spend all that money for a good detector when they're illegal in VA? Put that money towards some race tires. Also, just drive the speed limit, and you never have to worry about it.

my excuses are

(1) I was going to school in NC
(2) my drive home was ~5 hours
(3) ~50% discount on my beltronics rx65 pro because I work at crutchfield and had it legally sent down to NC
(4) my dad paid for it since he pays for my insurance

[Imprezivblue]

As far as using a detector on the highway, I never was a fan. Why spend all that money for a good detector when they're illegal in VA? Put that money towards some race tires. Also, just drive the speed limit, and you never have to worry about it.

my excuses are

(1) I was going to school in NC
(2) my drive home was ~5 hours
(3) ~50% discount on my beltronics rx65 pro because I work at crutchfield and had it legally sent down to NC
(4) my dad paid for it since he pays for my insurance

That's awesome! My dad's got a V1 and pays for my insurance and I jokingly hinted he should get me one for xmas. His response was he wasn't encouraging it and that he saw me chew through my last set of all season tires in 24k.

[ColinS]

That's awesome! My dad's got a V1 and pays for my insurance and I jokingly hinted he should get me one for xmas. His response was he wasn't encouraging it and that he saw me chew through my last set of all season tires in 24k.

My dad always tells me to not drive like an idiot and then quickly adds "but keep the radar detector on"