Stopping two cars

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hwybear
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Unread post by hwybear »

Reflections wrote:Lidar used by officers is invisible to the naked eye. You can however use nightvision to see them. I wonder why officers are not using nightvision to align the scopes???
I have used night vision to see the beam, very neat.

However, we are not trained/ qualified to align a scope. That must be done by the repair facility. What we do is ensure the unit is sighting properly, if the lidar fails the test, we place it out of service and send it for repair on the next Purolator truck.
Above is merely a suggestion/thought and in no way constitutes legal advice or views of my employer. www.OHTA.ca


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Unread post by hwybear »

Reflections wrote: One thing though. I know that light travels at a constant speed in a vacuum. The atmosphere is not a vacuum. Dirt, smog.....all those airbourne particles can effect light. How would this be compensated for....? I know you're coming back to this 'bear so..... The further away a target is from the gun the more the "light" is going to slow down, simple physics. Is there a setting you have for "smoggy" days??? I know there are foul weather modes on different models. You cannot compensate for the unknown.
To my use, I start observing vehicles about 1km away (through scope) monitor, then hit the vehicle with lidar around 700m. Then again around 550m. Then my final hit is around 500m-100m. This allows a visual observation, confirmed targetting history. The lidar beam is very concentrated being this close and any smog would be less than minimal affect.

The addition of moisture in the air reduces the effective range of the lidar. ie light rain might reduce my first reading from 700m down to 500m. Snow is just horrible and a waste of my time using a lidar. It is not affecting the accuracy of the readings, just how far away a vehicle can be targetted.
Above is merely a suggestion/thought and in no way constitutes legal advice or views of my employer. www.OHTA.ca


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hwybear
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Unread post by hwybear »

And at the end of the day, I would rather use lidar.

At 100m
Lidar = 30cm beam width
Radar = 20 metres

There is absolutely never any doubt with lidar which vehicle is travelling what speed.

although......my best is at night, obtain a speed via radar/lidar, catch the vehicle and then pace it....then pull up beside and READ the drivers speedometer. (even more icing on the cake when the speedometer is digital :shock: )
Above is merely a suggestion/thought and in no way constitutes legal advice or views of my employer. www.OHTA.ca


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Unread post by Reflections »

New civic's are very nice for you......

Your style is very thorough. Next time you have the oppertunity on a smoggy day, light someone up from 1 km and keep the gun on them. If the speed decreases the closer they get closer then there is some effect.

I know you'll say they let they're foot off the gas but this would help prove the theory.
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hwybear
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Unread post by hwybear »

Reflections wrote:New civic's are very nice for you......

Your style is very thorough. Next time you have the oppertunity on a smoggy day, light someone up from 1 km and keep the gun on them. If the speed decreases the closer they get closer then there is some effect.

I know you'll say they let they're foot off the gas but this would help prove the theory.
I'll give that a shot....pardon the pun!!
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Reflections
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Unread post by Reflections »

Just for giggles try it at night so they don't see you......
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Unread post by hwybear »

but won't know if it's smoggy :?
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Imax
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Unread post by Imax »

Is there a way of uploading pics on this forum? I have a few NURBS pics.


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Unread post by admin »

Imax wrote:Is there a way of uploading pics on this forum? I have a few NURBS pics.
The best way is to store your pictures on any free file storing website.

www.Photobucket.com is free and provides 1 GB of free space.

Once you have uploaded your picture you can simply post your picture/image on this forum using bbcode:

Code: Select all

[img]http://your-image-link-goes-here.com/image.jpg[/img]


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Imax
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Unread post by Imax »

thanks admin. It's working :lol:

NURBS setup. Two cars, one at 500m and one at 570m. Laser offset, 10m. The laser beam is a cone, 600m long and 1.8m at the base.

Image

A perspecive:

Image

Close up view:

Image

When looking at the close up, it’s not too bad. Any beam hitting the side of car one won’t be received by a lidar. But my NURBS model for car 1 and 2 aren’t realistic. They are two blocks, one on top of the other. I’ve missed on important aspect, side view mirrors.


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Unread post by Reflections »

Good shots and they explain a lot. As much as they are not "perfect" they do demonstrate the problems facing officers. The third one's the best.....good job.
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Unread post by hwybear »

maybe a mod can spilt this over to the law enforcement tools area... somewhere above this....
*************************************

seeing that a lane is 3.75m wide a typical car is 2.6m wide.......beam width is still less than the width of the car.

At 500m beam is 1.5m wide. One at 570m...round it to even 1.8m for simplicity sake.

Your "blocks" are realistic for Jeeps and Hummers :)
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Unread post by Reflections »

You can still see that it is difficult to target the plate..... And like you said you can't see the beam even under alignment checks. The officer still does not know "exactly" where the beam is.......at a distance of 500 meters 1 degree is a lot, even 0.5 degrees of misalignment will cause this situation.
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Unread post by racer »

hwybear wrote:maybe a mod can spilt this over to the law enforcement tools area... somewhere above this....
*************************************

seeing that a lane is 3.75m wide a typical car is 2.6m wide.......beam width is still less than the width of the car.

At 500m beam is 1.5m wide. One at 570m...round it to even 1.8m for simplicity sake.

Your "blocks" are realistic for Jeeps and Hummers :)
You are right, this thread is too long and discussion of lidars hijacked the thread. I shall have admin make me a mod for this section too and split it off.
"The more laws, the less justice" - Marcus Tullius Cicero
"The hardest thing to explain is the obvious"

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hwybear
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Unread post by hwybear »

Reflections wrote:You can still see that it is difficult to target the plate..... And like you said you can't see the beam even under alignment checks. The officer still does not know "exactly" where the beam is.......at a distance of 500 meters 1 degree is a lot, even 0.5 degrees of misalignment will cause this situation.
I still do not see it when the beam is not relative to the distance. Nor are the size of vehicles. It to one perspective is construed, something like stats are! :D
Above is merely a suggestion/thought and in no way constitutes legal advice or views of my employer. www.OHTA.ca


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