Probable Cause at 1160ft+ for using lidar...

**racerstodeath** · 10-26-04 02:06 AM

i was just wondering if this was justified... i am going to court on wed. and want to know if the cop had p.c.... he said that i was speeding 83 on 65 zone... at 1160 feef... thats the distance that the speed was clocked at... the environment is he was on the left shoulder and i was on the lane closest to the shoulder and that when he "clocked" me... any p.c.??

also i heard that at like 1200 feet, it is usually thrown out due to p.c...just wondering if this was true...

thanks for the help!

by the way... i don't race... its a childhood name i am stuck w/...hehe.. just to simplyify my logins into different forums....

**racerstodeath** · 10-26-04 02:11 AM

oh...yes... by the way i am in sugarland, texas...

and i was just wonder, i saw the police vehicle ahead of me .... far far away... like maybe 700 ft out or so... but the thing is i didn't really see him out of the vehicle... i was wonder if any police actually shoots the laser through the rear windshield... i have seen in a different circumstance.. that the police just opened the door and held the laser gun with his hands and sat on the driver's seat...

**JD45** · 10-26-04 02:34 AM

I've never heard of lidar being thrown out at 1200+ feet. There is a limit to how far you can use it and be effective.

You can shoot both lidar and radar through a windshield with no problem.

Sounds like the officer saw you coming, visually estimated you were speeding and then confirmed it with lidar, which is better than radar.

Just a side note, in some courts like in my county, if you plead not guilty and then ask for your day in court and are found guilty.....no traffic school for you. You'll have to pay up and take the point on your record. Just something to consider... :cool:

**Piggy** · 10-26-04 02:39 AM

You heard wrong. Good like fighting a laser ticket. It's about as accurate as you can get. PC, or probable cause it what an Officer needs to make a stop. He had that as the crosshairs on his laser beam can hit you from over well over the distance you have posted. As it's an infraction, unless the state your in is different, he'll just need to make his case against you on a preponderance of the evidence. And yes, it will work through a rear window.

**Piggy** · 10-26-04 03:02 AM

Here's some info from the site "how stuff works". Cool site for information you'll probably never use and it kills some great time!!!

How does a laser speed gun work to measure a car's speed?

If you have read the article entitled How Radar Works, then you know how normal radar works. A normal radar set sends out a radio pulse and waits for the reflection. Then it measures the doppler shift in the signal and uses the shift to determine the speed.
The new laser speed guns use a more direct method that relies on the reflection time of light rather than doppler shift. You have probably experienced the reflection time of sound waves in the form of an echo. For example, if you shout down a well or across a canyon, the sound takes a noticeable amount of time to reach the bottom of the well and travel back to your ear. Sound travels at something like 1,000 feet (300 meters) per second, so a deep well or a wide canyon creates a very apparent round-trip time for the sound.

A laser speed gun measures the round-trip time for light to reach a car and reflect back. Light from a laser speed gun moves a lot faster than sound -- about 984,000,000 feet per second (300,000,000 meters), or roughly 1 foot (30 cm) per nanosecond. A laser speed gun shoots a very short burst of infrared laser light and then waits for it to reflect off the vehicle. The gun counts the number of nanoseconds it takes for the round trip, and by dividing by 2 it can calculate the distance to the car. If the gun takes 1,000 samples per second, it can compare the change in distance between samples and calculate the speed of the car. By taking several hundred samples over the course of a third of a second or so, the accuracy can be very high.

The advantage of a laser speed gun (for the police anyway) is that the size of the "cone" of light that the gun emits is very small, even at a range like 1,000 feet (300 meters). The cone at this distance might be 3 feet (1 meter) in diameter. This allows the gun to target a specific vehicle. A laser speed gun is also very accurate. The disadvantage is that the officer has to aim a laser speed gun -- normal police radar with a broad radar beam can detect doppler shift without aiming.

**racerstodeath** · 10-26-04 03:04 AM

i did this little test at home... things i remembered from physics class... when light (laser) goes through a medium like glass at an angle... it changes the laser's direction... you can do this at home... use a clean glass, angle it 45 degrees or so... and shoot a laser pointer through it... at 45 degrees, it will reflect it totally... going at any angle perpendicular to the glass... just my 2 cents tho...

also.. it seems like that New Jersey limits its laser use to 1000 ft...

"Some states limit or restrict laser radar use. A New Jersey Appeals Court upheld (in a 2-1 decision) a lower court ruling (based on the LTI Marksman 20-20 lidar) that leaves in place restrictions on laser radar use. New Jersey Troopers can only use laser radar in clear weather and for targets less than 1000 feet.
Sources:
-- National Motorists Association NEWS, Jan/Feb 2000, vol 11, issue 1.
-- STATE OF NEW JERSEY v. EMAD A. ABESKARON, A-107-98T2F, 24 Nov 1999"

just found this after the post... let me know your 2 cents!

**racerstodeath** · 10-26-04 03:07 AM

Originally Posted by Piggy

The advantage of a laser speed gun (for the police anyway) is that the size of the "cone" of light that the gun emits is very small, even at a range like 1,000 feet (300 meters). The cone at this distance might be 3 feet (1 meter) in diameter. This allows the gun to target a specific vehicle. A laser speed gun is also very accurate. The disadvantage is that the officer has to aim a laser speed gun -- normal police radar with a broad radar beam can detect doppler shift without aiming.

just thinking... don't the police have to hold on to the laser really really straight? i mean... things like breathing... would create like movement at the hands...but at 1160 ft... in my case... would move it a lot right... gonna do some calculations... hehe...

**Piggy** · 10-26-04 03:14 AM

It does have to be held quite still, but then again it's been a few years since I used lidar. Technology could have changed since then. I know you said you were from Texas but you also mentioned NJ. Where did you get the ticket? If it is in NJ you may have a better case than in Texas if you cite that court case.

The big question is, were you going that fast?

**racerstodeath** · 10-26-04 03:19 AM

Originally Posted by JD45

Sounds like the officer saw you coming, visually estimated you were speeding and then confirmed it with lidar, which is better than radar.

just some more...rambling... the reason why i am asking about p.c. is because the police was so close angle wise to my vehicle... from his angle... it would be looking at the vehicle staight ahead... now i am not a police... duh!... but i mean... if he took the speed at 1160ft ... that means... he would have to estimate the speed of the vehicle (about 4 inches from his position) and get the gun and shoot it... by 1160 ft... now considering... if i was actually going 85 mph at the time, i would be traveling at 124.66 ft per second... if it only took him 2 seconds to do everything above, it would be a total ft of 1409.32 ft!!! thats more than a quater of a mile! and then not to mention tracking history... could he actually have track the vehicle w/o losing sight of the vehicle? i am not going into that one cuz no ones knows...

**Piggy** · 10-26-04 03:22 AM

So how fast were you going?

**racerstodeath** · 10-26-04 03:24 AM

well.. truthfully... i don't know... cuz i was on the middle lane and there was this big 18 wheeler... and so i proceeded to the left lane to pass him... accelerated.... and at this time there were this brown f150/f350 infront of me... saw him slow down...so i slow down... and he moved to the middle lane... i kept on left lane and proceeded at speeds LOWER than 45 mph... i know for sure cuz in texa you have to go 20 mph slower than the posted if a police vehicle is on the side of the road...

**racerstodeath** · 10-26-04 03:27 AM

oh by the way... this is really close to houston...so i mean almost all cars travel faster than posted... right lane is like 5+ more than posted and the left lane is like for 80 and above...

**Piggy** · 10-26-04 03:28 AM

So you think you were going somewhere in between 40-45 mph?

**JD45** · 10-26-04 03:28 AM

Originally Posted by racerstodeath

just thinking... don't the police have to hold on to the laser really really straight? i mean... things like breathing... would create like movement at the hands...but at 1160 ft... in my case... would move it a lot right... gonna do some calculations... hehe...

the one I use has a HUD with a nice recticle so you're always on target..

**Piggy** · 10-26-04 03:32 AM

Originally Posted by JD45

the one I use has a HUD with a nice recticle so you're always on target..

NICE!!!! I'll bet its an expensive toy. :D

This ad will disappear if you login

Thread: Probable Cause at 1160ft+ for using lidar...

Thread Tools

Display

Probable Cause at 1160ft+ for using lidar...

not trying to argue but...

stilll not arguing hehe...

Posting Permissions