Do scamera vans work in the rain?
Discussion
They certainly werent approved for use in the rain. How can they be: with millions of tiny lenses between the device and its target? They didnt used to be approved for use after dusk either, although I believe that either some new, or all kit retrospectively, has been approved for use at night, now.
Tough luck, Bill:
http://www.humbersidesafetycameras.com/about-safet...
http://www.humbersidesafetycameras.com/about-safet...
Scamera people said:
cameras operate effectively in poor light conditions, including night-time and also in rain and snow without the beam being refracted by water drops
You can always say it was SWMBO... 
It was her car 
But as I wasn't speeding it's a moot point.
N Dentressangle said:
Tough luck, Bill:
http://www.humbersidesafetycameras.com/about-safet...
So the police/SCP bend the truth - what's new! Now SCP lasers are immune to the laws of physics - reflection/refraction/opacity!http://www.humbersidesafetycameras.com/about-safet...
Scamera people said:
cameras operate effectively in poor light conditions, including night-time and also in rain and snow without the beam being refracted by water drops
You can always say it was SWMBO... Lidar: yes they work in the rain (although the older UL 100 struggled a bit).
Basically, if you can see the target vehicle, then there’s no reason why the laser wouldn’t get through. If you can't see the target, then you obviously can't form opinion of speed.
The usual outcome is a reduction of working range. At worst, the gun will simply read E01 if the rain is too heavy and the target is too distant.
1 inch per hour of rain is considered heavy. Rain falls at about 20mph. Therefore, that 1 inch translates to 20 vertical miles in air. From this, the density of rain water in air is trivial to calculate (about 1ppm). Therefore, there is very little water in a given volume of rain.
Reflection: far too weak (small and round droplet) and spread out (time wise), compared to strong and temporally concentrated reflection from registration plates. Reflections from nearby droplets will be filtered out by the timed gating of the gun.
Refraction 1): water has an RI of 1.333. In order to get an error of 2mph at 70mph (these figures represent the worst case scope for geometric error) which is a factor of 1.0286, the water density would have to be about 12% (120000ppm)
Refraction 2): Light can certainly be bent by rain, but to get exactly the same optical path, 35 times (out of 40), by something so random, and so few and far between, is beyond reasonable. So even if reflections from droplets were strong enough to be received by the gun, the unreasonable variance of distance (for each sample) will mean the error trapping will trigger and void the attempt at a speed deduction.
Opacity: 1ppm. That’s effectively 1mm of water per km. I can easily view objects under +1000mm of water; so opacity cant be a problem.
Basically, if you can see the target vehicle, then there’s no reason why the laser wouldn’t get through. If you can't see the target, then you obviously can't form opinion of speed.
The usual outcome is a reduction of working range. At worst, the gun will simply read E01 if the rain is too heavy and the target is too distant.
1 inch per hour of rain is considered heavy. Rain falls at about 20mph. Therefore, that 1 inch translates to 20 vertical miles in air. From this, the density of rain water in air is trivial to calculate (about 1ppm). Therefore, there is very little water in a given volume of rain.
Reflection: far too weak (small and round droplet) and spread out (time wise), compared to strong and temporally concentrated reflection from registration plates. Reflections from nearby droplets will be filtered out by the timed gating of the gun.
Refraction 1): water has an RI of 1.333. In order to get an error of 2mph at 70mph (these figures represent the worst case scope for geometric error) which is a factor of 1.0286, the water density would have to be about 12% (120000ppm)
Refraction 2): Light can certainly be bent by rain, but to get exactly the same optical path, 35 times (out of 40), by something so random, and so few and far between, is beyond reasonable. So even if reflections from droplets were strong enough to be received by the gun, the unreasonable variance of distance (for each sample) will mean the error trapping will trigger and void the attempt at a speed deduction.
Opacity: 1ppm. That’s effectively 1mm of water per km. I can easily view objects under +1000mm of water; so opacity cant be a problem.
smeggy said:
Reflection: far too weak (small and round droplet) and spread out (time wise), compared to strong and temporally concentrated reflection from registration plates. Reflections from nearby droplets will be filtered out by the timed gating of the gun.
Refraction 1): water has an RI of 1.333. In order to get an error of 2mph at 70mph (these figures represent the worst case scope for geometric error) which is a factor of 1.0286, the water density would have to be about 12% (120000ppm)
Refraction 2): Light can certainly be bent by rain, but to get exactly the same optical path, 35 times (out of 40), by something so random, and so few and far between, is beyond reasonable. So even if reflections from droplets were strong enough to be received by the gun, the unreasonable variance of distance (for each sample) will mean the error trapping will trigger and void the attempt at a speed deduction.
Opacity: 1ppm. That’s effectively 1mm of water per km. I can easily view objects under +1000mm of water; so opacity cant be a problem.
I am not a physicist and I am quite drunk but...could it potentially refract the beam into the next lane?Refraction 1): water has an RI of 1.333. In order to get an error of 2mph at 70mph (these figures represent the worst case scope for geometric error) which is a factor of 1.0286, the water density would have to be about 12% (120000ppm)
Refraction 2): Light can certainly be bent by rain, but to get exactly the same optical path, 35 times (out of 40), by something so random, and so few and far between, is beyond reasonable. So even if reflections from droplets were strong enough to be received by the gun, the unreasonable variance of distance (for each sample) will mean the error trapping will trigger and void the attempt at a speed deduction.
Opacity: 1ppm. That’s effectively 1mm of water per km. I can easily view objects under +1000mm of water; so opacity cant be a problem.
I suspect the answer is in the millions/billions to one, but I wondered regardless and I'm not shy of asking stupid questions
smeggy said:
Lidar: yes they work in the rain (although the older UL 100 struggled a bit).
Basically, if you can see the target vehicle, then there’s no reason why the laser wouldn’t get through. If you can't see the target, then you obviously can't form opinion of speed.
The usual outcome is a reduction of working range. At worst, the gun will simply read E01 if the rain is too heavy and the target is too distant.
1 inch per hour of rain is considered heavy. Rain falls at about 20mph. Therefore, that 1 inch translates to 20 vertical miles in air. From this, the density of rain water in air is trivial to calculate (about 1ppm). Therefore, there is very little water in a given volume of rain.
Reflection: far too weak (small and round droplet) and spread out (time wise), compared to strong and temporally concentrated reflection from registration plates. Reflections from nearby droplets will be filtered out by the timed gating of the gun.
Refraction 1): water has an RI of 1.333. In order to get an error of 2mph at 70mph (these figures represent the worst case scope for geometric error) which is a factor of 1.0286, the water density would have to be about 12% (120000ppm)
Refraction 2): Light can certainly be bent by rain, but to get exactly the same optical path, 35 times (out of 40), by something so random, and so few and far between, is beyond reasonable. So even if reflections from droplets were strong enough to be received by the gun, the unreasonable variance of distance (for each sample) will mean the error trapping will trigger and void the attempt at a speed deduction.
Opacity: 1ppm. That’s effectively 1mm of water per km. I can easily view objects under +1000mm of water; so opacity cant be a problem.
Try some more googling. Obviously in very light rain there won't be much of an issue, any more than that, they cannot be used effectively, although some people (including the manufacturers) would like you to think otherwise.Basically, if you can see the target vehicle, then there’s no reason why the laser wouldn’t get through. If you can't see the target, then you obviously can't form opinion of speed.
The usual outcome is a reduction of working range. At worst, the gun will simply read E01 if the rain is too heavy and the target is too distant.
1 inch per hour of rain is considered heavy. Rain falls at about 20mph. Therefore, that 1 inch translates to 20 vertical miles in air. From this, the density of rain water in air is trivial to calculate (about 1ppm). Therefore, there is very little water in a given volume of rain.
Reflection: far too weak (small and round droplet) and spread out (time wise), compared to strong and temporally concentrated reflection from registration plates. Reflections from nearby droplets will be filtered out by the timed gating of the gun.
Refraction 1): water has an RI of 1.333. In order to get an error of 2mph at 70mph (these figures represent the worst case scope for geometric error) which is a factor of 1.0286, the water density would have to be about 12% (120000ppm)
Refraction 2): Light can certainly be bent by rain, but to get exactly the same optical path, 35 times (out of 40), by something so random, and so few and far between, is beyond reasonable. So even if reflections from droplets were strong enough to be received by the gun, the unreasonable variance of distance (for each sample) will mean the error trapping will trigger and void the attempt at a speed deduction.
Opacity: 1ppm. That’s effectively 1mm of water per km. I can easily view objects under +1000mm of water; so opacity cant be a problem.
roachcoach said:
I am not a physicist and I am quite drunk but...could it potentially refract the beam into the next lane?
I suspect the answer is in the millions/billions to one, but I wondered regardless and I'm not shy of asking stupid questions
The issue isn't the probability of "refracting the beam", but the probability of refracting the beam in exactly the same way (within a few cm), for (about) 35 out of 40 samples, each sample with a totally different distribution of droplets, all affecting the optical paths in different ways.I suspect the answer is in the millions/billions to one, but I wondered regardless and I'm not shy of asking stupid questions
The LTIs don't do just one ping, they do a great many, and the result of each ping must follow a precise pattern otherwise the speed reading is aborted.
Mr GrimNasty said:
Try some more googling.
I don't google this stuff; do you think I googled those explanations? (google it yourself and see where it gets you)Indeed it seems the accuser is actually the one guilty - don't judge me by your low standards!
I currently have 3 different LTIs in my possession; I have also examined their innards (yes with an oscilloscope - I have even seen the 'gating' in action). On this forum I have proven myself quite hot with maths, optics and physics (the 150mph biker).
Mr GrimNasty said:
Obviously in very light rain there won't be much of an issue, any more than that, they cannot be used effectively, ....
And how do you know that? (googling?) What is your reasoning for that statement please.I have often found it amusing that folks, who have no clue how an LTI actually operates and have never held one, claim they know how they work better than those who actually have used them and know how they actually work.
Facts: rain does not affect targeting, or the speed and distance readings of LTIs. Rain can affect the range performance of the older UL100 (although the various settings help to alleviate related issues), but the TSM Speedscope (the LTI of choice in the UK) will work fine.
It has been raining today, on and off, with some heavy spurts. I did some actual tests with real equipment.
With light and medium rain, both the TSM and UL100 reliably and accurately picks off a target 400m away.
With heavy rain, the UL100 doesn't lock on to the target 400m away, but it does just fine with targets 100-200m away. The TSM seemingly wasn't affected at all. This isn't news to anyone who has actually used an LTI.
If you manage to google something that says different, let me know so I can correct your source!
smeggy said:
The issue isn't the probability of "refracting the beam", but the probability of refracting the beam in exactly the same way (within a few cm), for (about) 35 out of 40 samples, each sample with a totally different distribution of droplets, all affecting the optical paths in different ways.
The LTIs don't do just one ping, they do a great many, and the result of each ping must follow a precise pattern otherwise the speed reading is aborted.
That'll do The LTIs don't do just one ping, they do a great many, and the result of each ping must follow a precise pattern otherwise the speed reading is aborted.
These forums need a "thanks" or similar function
smeggy said:
It has been raining today, on and off, with some heavy spurts. I did some actual tests with real equipment.
With light and medium rain, both the TSM and UL100 reliably and accurately picks off a target 400m away.
With heavy rain, the UL100 doesn't lock on to the target 400m away, but it does just fine with targets 100-200m away. The TSM seemingly wasn't affected at all. This isn't news to anyone who has actually used an LTI.
If you manage to google something that says different, let me know so I can correct your source!
Don't do that! With light and medium rain, both the TSM and UL100 reliably and accurately picks off a target 400m away.
With heavy rain, the UL100 doesn't lock on to the target 400m away, but it does just fine with targets 100-200m away. The TSM seemingly wasn't affected at all. This isn't news to anyone who has actually used an LTI.
If you manage to google something that says different, let me know so I can correct your source!
Erroneous information that erodes public confidence in LTI "dodgyscopes" is not all bad.
fluffnik said:
Erroneous information that erodes public confidence in LTI "dodgyscopes" is not all bad.
It is to those who have lost up to £10k on a failed court case, based on dodgy info they glean from the web from wannabee experts. There are too many such failed cases.These guns do have problems worthy of close scrutiny (e.g. slip, and the wider issue of RTTM), so I think we should focus on those, instead of diverting ourselves to non-issues and losing credibility in the process.
smeggy said:
The issue isn't the probability of "refracting the beam", but the probability of refracting the beam in exactly the same way (within a few cm), for (about) 35 out of 40 samples, each sample with a totally different distribution of droplets, all affecting the optical paths in different ways.
So you're saying it is possible to be affected, just highly unlikely?Gassing Station | Speed, Plod & the Law | Top of Page | What's New | My Stuff