# How does lidar work on Curvy roads



## vjk (May 1, 2007)

Hi I got a speeding ticket uphill curvy road.
I am sure i was not goign the speed indicated on the ticket.
Where do i find information on LIDAR and how accurate it is on a curvy road.
Any information is appreciated.
Thanks!!!


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## DB82 (Dec 24, 2004)

It's just simply magic.

I hate how the company spelled LIDAR wrong on the citation, if infact it's true to Police Officer wrote the wrong speed on your cite. :FM:


Haha god speed vjk with the rest of them


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## USMCRoryT (Mar 29, 2007)

It took me a minute to get the joke, but HAHAHA...


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## Guest (May 1, 2007)

I don't get it........


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## rdmj72 (Sep 5, 2004)

"lie"dar..........


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## justanotherparatrooper (Aug 27, 2006)

vjk said:


> Hi I got a speeding ticket uphill curvy road.
> I am sure i was not goign the speed indicated on the ticket.
> Where do i find information on LIDAR and how accurate it is on a curvy road.
> Any information is appreciated.
> Thanks!!!


They have straight LIDAR and curved LIDAR, just make sure the officer was certified with curved LIDAR...Youve got a good shot at beating the ticket.


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## CJIS (Mar 12, 2005)

justanotherparatrooper said:


> They have straight LIDAR and curved LIDAR, just make sure the officer was certified with curved LIDAR...Youve got a good shot at beating the ticket.


LOL
good one

Oh and in answer to the question just pay the ticket LIDAR is accurate be it on a straightaway or on S curves. Up or down a hill does not matter.


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## phuzz01 (May 1, 2002)

vjk said:


> Hi I got a speeding ticket uphill curvy road.
> I am sure i was not goign the speed indicated on the ticket.
> Where do i find information on LIDAR and how accurate it is on a curvy road.
> Any information is appreciated.
> Thanks!!!


Well, the LIDAR is clocking how fast you are traveling towards it, so if anything, you were actually going a little faster than cited. Maybe we should just add a few mph to the reading on cuves. :mrgreen:


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## vjk (May 1, 2007)

Considering trignometry it depends if the speed calculated is more or less then the actual speed depending if the officer is located uphill or a downhill slope.
Is there a way to find this information?
Thnx


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## dcs2244 (Jan 29, 2004)

vjk said:


> Considering trignometry it depends if the speed calculated is more or less then the actual speed depending if the officer is located uphill or a downhill slope.
> Is there a way to find this information?
> Thnx


Your thinking of the "cosine angle of deviance" which shouldn't be a factor in this case...


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## Mikey682 (May 2, 2002)

Hey, lets help a speeder get out of a ticket!


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## Guest (May 1, 2007)




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## CJIS (Mar 12, 2005)

Trolls have got to eat too!


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## vjk (May 1, 2007)

dcs2244 said:


> Your thinking of the "cosine angle of deviance" which shouldn't be a factor in this case...


Thnx for the reply!!!
I was thinking in terms of:
If the cop was at the bottom of slope and I am going downhill taking the angle into consideration it would show decreases speed and If I am goign uphill the hill and cop is at the top it would show increases speed? Adding to that it was a curvish road.


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## Pacman (Aug 29, 2005)

All of which would be confirmed via the lidar reading. Face it slick, you broke the law and got popped. Suck it up and pay the fine.


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## dcs2244 (Jan 29, 2004)

vjk said:


> If the cop was at the bottom of slope and I am going downhill taking the angle into consideration it would show decreases speed and If I am goign uphill the hill and cop is at the top it would show increases speed?


No, because you are both in the same reference plane. It is more work to speed uphill than to speed downhill as you must overcome gravity uphill rather than being assisted by gravity when going downhill...F=MA and all that...


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## vjk (May 1, 2007)

dcs2244 said:


> No, because you are both in the same reference plane. It is more work to speed uphill than to speed downhill as you must overcome gravity uphill rather than being assisted by gravity when going downhill...F=MA and all that...


Sorry. Did not mean to say i was accerating whiel goign uphill
Rephrasing
_If the cop was at the bottom of slope and I am going downhill taking the angle into consideration it would show *decreased* speed and If I am goign uphill the hill and cop is at the top it would show *increased* speed?_


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## Guest (May 2, 2007)

posts like this are the reason why I love this site. They just dont get it.


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## justanotherparatrooper (Aug 27, 2006)

shocker911 said:


> posts like this are the reason why I love this site. They just dont get it.


*you just gotta love publik edukashion*


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## USMCTrooper (Oct 23, 2003)

The cosine angular effect measures your speed lower than it actually is, by varying degrees depending on the angle. 

It takes a significant angle however to get a measurment drastically lower than what the vehicle is really traveling.

For example, a vehicle going 70 mph will register on a LIDAR as 69.99 at a 1 degree angle. At a 15 degree angle the same vehicle at 70 mph will register as 67.61 mph This works to benefit the driver, not the police.

It isn't until you reach an angle greater than 45 degrees that the speed records in at 30 mph off of what the vehicle is actually traveling.

In short, an cosine angular effect will only help the violator. If the LIDAR read 70 and you feel there was a cosine angle, you were going faster than 70 by either 1/100th of a mph or up to 30 mph faster. Either way, you lose.


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## phuzz01 (May 1, 2002)

vjk said:


> Sorry. Did not mean to say i was accerating whiel goign uphill
> Rephrasing
> _If the cop was at the bottom of slope and I am going downhill taking the angle into consideration it would show *decreased* speed and If I am goign uphill the hill and cop is at the top it would show *increased* speed?_


You are talking about two different things here: hills, and curves.

A hill should not have any effect on the reading, since the officer standing at the top or bottom is still operating it along the same plane as the target.

A curve or an angle can create a cosine effect, because less than 100% of your motion is directed right at the LIDAR unit. However, that will always result in a speed reading that is lower than your actual speed.

The only way a LIDAR can read higher than your actual speed is if the operator is generating extra motion by swinging the LIDAR unit around. 99 times out of 100, the LIDAR unit is going to start getting inconsistent readings if you do that, and it won't give you a target lock and a speed output. Also, a trained operator knows to keep the unit as still as possible. So if the officer is trained and certified, you (and the courts) can assume that this was not an issue.


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## SOT (Jul 30, 2004)

Just fine. LIDAR works fine on curves and hills.

But seriously why not just ask the freaking real question:
How do I beat my LIDAR ticket in court.
That's what this is really about right? I mean you were speeding, you got caught, and you are looking for a way out.
Are you saying you were not speeding at all? Were you speeding a little?
Face it, the short version of this answer is go to court and figure it out. You are an absolute DUMB ASS for coming to a cop site to try and get help on beating a ticket.


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## Killjoy (Jun 23, 2003)

LIDAR is all a scam anyways...our department just painted a cereal box and glued some PVC pipe to it. We just point it at oncoming traffic and hope people slow down.


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## dcs2244 (Jan 29, 2004)

USMCTrooper said:


> The cosine angular effect measures your speed lower than it actually is, by varying degrees depending on the angle.
> 
> It takes a significant angle however to get a measurment drastically lower than what the vehicle is really traveling.
> 
> ...


How do you like that? USMCtpr horning in on my "geekdom"! I'll deal with you later, bub.


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## dcs2244 (Jan 29, 2004)

Wolfman said:


> Take him out of the mix and now see what's happened...


Yeah, he sits across the room noshing on twizzlers and failing to treat me to lunch at the Bonnet! Oh, and raiding my life-saver stash!

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## SOT (Jul 30, 2004)

Here's the cosign tool for LIDAR.










This is the speed version, does the quick calculations in the field.


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## vjk (May 1, 2007)

Thnx for info USMCTrooper!!!


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## dcs2244 (Jan 29, 2004)

vjk said:


> Thnx for info USMCTrooper!!!


Swell, I broach the subject and Miles Archer gets the credit...


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## vjk (May 1, 2007)

Thnx Officer dcs!!!


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## OutOfManyOne (Mar 2, 2006)

Lidar is cool, it shoots laser beam around 90 degree corners to catch speeders and are able to bounce the beam of four different vehicles to get the violator's speed. It can also do other neat stuff but that is confidential on a need to know basis.


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