Safe Speed Forums

a laser has limited use on water for the following reasons.

1.) it will only ever measure the differential in speed between two objects.

on the road this is simple to achieve as the source of the laser is typically stationary. if the source of the laser is doing 10 mph towards a stationary object the device will show 10 mph. if the target is closing on the source at 10 mph as well then the device will read 20 mph. in order to sustain viable laser evidence the patrol Muppets will also have to record their speed at the exact time as they use the device to measure the differential. This is hard and I don't think they currently do that. ergo. The reading shown should be regarded as only a differential.

2.) Trigonometry and vectoring

When a bonafide Police officer uses a laser device on the road he can be sure of one thing. That is the direction from which the target will come. On the Lake that is not so. If you are to remember back to the good old days of skool you will remember trigonometry and how you calculate the length of a side of a triangle using a mathematical formula. If the Muppets want to use a laser they cannot simply point and squirt the device at something as it drives across their path. If they do so all they are actually doing is measuring the change in distance between them and the target. Explained simply, If a target drives at 50 mph in parallel to the source and the source is also doing 50 mph then the reading will be zero. Or put another way. If the target drives at the source at 50 mph and it is 0 degrees to the source the device will read 50 mph. a few seconds later when the target is at 45 degrees to the source it will read 25mph. a few seconds later still when the target is at 90 degrees to the source the device will (should) read zero. Later still -25mph. later still -50 mph. this also starts to dwell on the safety issue as the Muppet will have to position themselves directly into the path of the speeding boat in order to take any form of accurate reading and also see point 1. At a guess the maximum source to target beam angle to be accurate can only be in the region of 5 degrees. Traffic police achieve this by being on a bridge over or within 3 meters of the targets path.

3.) Range and distance to target.

In order for the device to measure accurately measure a speed it must take an average of readings. For it to do this the beam must be accurately aimed at the target for about 2 seconds so that the device may take a few readings and average them out. On the road this is a simple task as the source tends to be fixed and most officer's rest the device on the car to get it steady enough to function properly. Range plays an important part in the detection of speeders. A traffic officer knows that the greater the range at which a target is detected the better the chance of getting a reading and a conviction from it. Example. If you take a laser pen and try to shine it on a specific spot it's easy to do it at only a few meters but at longer ranges this becomes increasingly difficult. Also add to the level of difficulty by instead of been on land you are on a moving floating platform, on a lake, with a less then flat surface, with a hand held device and I hope you can see where I'm coming from. That is, its hard to get any form of bead on the target at anything other than very short ranges. At a guess the max range would have to be around 50 to 100 meters. Also see point 2. Also bear in mind that unlike the laser pen with a bright red dot and a significant amount of beam divergence (making it easier to see at range) the lake Muppet cannot see the beam on the target he only has a crosshair gun sight to use at arms length. The Muppet should have to declare the sea state, range and probably several separate readings from the target to sustain a conviction

4.) skip and reflections

If you talk to a Traffic patrol officer he will tell you the easiest thing to get a good reading from is a Kawasaki motorbike. This is because is has two great big headlamps close together that make a fantastic laser reflector. Boats on the hole don't have highly reflective headlamps or number plates at which to shine a laser and I am quite surprised they can get it to work at all. (The early trials with Radar gun's failed because there was nothing solid enough to reflect the radar energy apart from the engines rotating parts and this caused very spurious readings.)

I say this because I have tried to do it on a race boat for the filming of a Clarkson TV program. The attempt took place at the National water sports centre near Nottingham a couple of years ago and Mr Plod was in attendance. At no point could he get a reading off the boat as it was just too curved to reflect well. What instantaneous readings he could get were spurious and caused by reflections from the water, which brings me onto skip. The road unlike the multifaceted surface of the lake does not reflect and a laser device is designed around this fact. I'm not sure that the manufacturer of the device actually rates it's for the gathering of evidence on water against boats and we should try to find out who manufactures the device in order to clarify this situation. I will do this if someone will tell me who makes it and its model number. I have also tried to use a beam device to create a finish line but have had no success mainly because of skipping and the light beam being reflected from the surface to a point before the actual finish line. This would cause a false reading

5.) Covert speeding and stealth

Turn away from the device if you see it being used, paint the outfit matt black with no vertical shiny surface. As a driver, if you see the device being used against someone drive very close to the Muppet boat to unsettle it. Fit a mirror ball behind the windscreen and rotate it over twice a second (120 rpm) - this would be illegal on the road but no law preventing the use of such a device exists for the water as far as I am aware. Try the euro trucker's trick of putting a load of CD's along the bottom of the windscreen. Don't dive at stationary boats with uniformed Muppets on board. Don't worry if they are moving as they probably cannot use the device against you

6. sustainability

In order to sustain a conviction the Muppet will have to do the following

Log the water state, speed of their own craft including drift and probably wind speed and other weather information. Note the compass direction angle at which the reading was been taken. Note the direction of the target. Note the range to the target. Understand and demonstrate in court that they understand the limitations of the device. I believe this is why they have yet to use such evidence in court and Tony should ask why such evidence was not taken at the time of his activity. This would help in future cases when they actually get round to trying it on.

It is technically possible to create a device that measures the speed of a vessel from any point to any point and given enough money someone or some organisation could but in their current fiscal state I'd be surprised if they can afford to get the patrol team to work outside of their current patrol hours.

we should if I am correct in my assumptions publicise these limitations to put this particular fire out.

All this of course is not withstanding the fact that a beam of light shot from a moving object will travel a distance in the same time as one shot from a stationary object which is the fundamental building blocks of physics as we know today and the essence of why relative time travel is possible blah blah blah

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Apparently the water gestapo were two miles away though, how on earth can you guesstimate or form an opinion of speed wo miles away?

Now in the Sun , some photos of a french catermaran copying Donald Campbells flip at 110 MPH.

Big difference to Bluebird. It weighed two and a half tons, being powered by a Metro-Vickers turbo-jet engine generating 4000 horse-power!
The Catamaran in the pictures was in a situation they find themselves in regularly throughout the season.

Power is nothing without control!