Fine or no fine?

[Pancakes]

Somebody correct me if I'm wrong but as I understand it the doppler effect can only show you how fast an object is moving relative to you, not it's absolute speed. The speed of the vehicle changes the emitted and received frequency.

Yeah dude, the units "brain" would say that the objects to the extreme left and right must be the side of the road or that the big flat think it sees infront is the road (or that it might see 100 objects, 40 cars, and 60 houses, trees, signs some road etc and assume all those things doing the same speed are doing 0km/h) and will use the relative speed compared to whatever that thing is it is programmed to see as the surroundings as the police vehicle speed then the target actual speed is easily calculated. IE, Cop car is doing 95km/h compared to all the not moving things around it and the target is doing 20km/h away from the cop car the target is doing 115km/h.

Did you even read any bit of the stacks of information about this in the thread?

[Pancakes]

A CD is designed as a laser reflector, so having CDs all over the car will make it easier to give the cop's laser a target. I'm sure that the HP appreciate the help.

I think laser uses the same system that they use for measuring how close the moon is etc, if you have a laser and lens at one point and turn it on it takes a set amount of time for the light to travel and hit an object (and twice that time before someone at the same place as the laser see's it). So all you need to do is have a pulsed laser and timer, if the thing the laser is hitting is getting closer at a set rate every 100th of a second (or whatever the pulse rate is for a laser gun) it must be getting closer at that speed. I haven't included that maths cos the speed of light and all that is boring.

[Patrick]

should I get on to calling his C/O like u suggest. Also I've heard he is the C/O !!

Yes, and ask for his supervisor, a Senior Sergeant or his Sergeant (I don't think he has been promoted yet... he is a Senior Constable.)

I recall hearing that at the time of the introduction of instant fines for infringment offences, a number Ministry of Handsports traffic cops quit in protest, which ironically left only those with dubious consciences.

They then became meter maids...

Police Radar units have two target speeds...

Not bad... sounds like that....

First off, although a metallic surface is a good reflector of radar, it is by no means necassary.... In the case of Desert road... it reflects off the road in front....

I heard cats eyes can reflect a signal too... there are lots of those on the Desert..

In heavy rain it is VERY difficult for the police to use there radar equipment because or rain clutter.. or the radar reflecting back off the rain drops..

Unless it is stationary. But if heavy rain, even stationary won't work.

So do the nz police radars, every shift they are used, and fill in the log book after testing is complete.

Once a day.... three shifts in a day, but only once a day...

Really. Very interesting, as I have a letter dated yesterday that states precisely the opposite. So who's wrong?

Radar or laser? Radar needs to be tested daily, that day if used that day....

[Renegade]

Once a day.... three shifts in a day, but only once a day...[/B]

Radar or laser? Radar needs to be tested daily, that day if used that day....

The log book is there, might as well test the device, be it radar or laser, at least that way you can stand up in court and say "i tested it and it was working fine", cant rely on other people.

[Max Preload]

Somebody correct me if I'm wrong but as I understand it the doppler effect can only show you how fast an object is moving relative to you, not it's absolute speed. The speed of the vehicle changes the emitted and received frequency.

The reason for the low reading may have been what is referred to as the COSINE effect (the adjacent side of the vector triangle is registered speed - finally all those hours of high school trigonometry pays off lol) because the target direction is not accounted for in the mircowave units, so unless you're moving directly towards the unit your speed will register low (advantage target!).

Perhaps I could have explained that better. Yes, only your speed towards the patrol (or more correctly the source of the microwave) is calculated with the doppler effect.

[Max Preload]

I recall hearing that at the time of the introduction of instant fines for infringment offences, a number Ministry of Handsports traffic cops quit in protest, which ironically left only those with dubious consciences.

They then became meter maids...

I suddenly have so much more respect for meter maids.

[swbarnett]

Did you even read any bit of the stacks of information about this in the thread?

Yes, I did. I read it to mean a single object, not an aggregate of multiple. Thanks for the reply, this makes sense.

Perhaps I could have explained that better. Yes, only your speed towards the patrol (or more correctly the source of the microwave) is calculated with the doppler effect.

Are you saying that the radar is not used to calculate the speed of the source vehicle? i.e what pancakes said about the majority of objects being stationary?

[Max Preload]

Are you saying that the radar is not used to calculate the speed of the source vehicle? i.e what pancakes said about the majority of objects being stationary?

No - that's not what I'm saying. I'm sure that the patrol vehicle display is from the microwave unit, not a mechanical input. What I'm saying is that your relative speed towards the patrol is what is displayed. That is to say if travelling at a direction of 45 deg to the patrol doing 100km/h it will only register 71km/h (cosine effect) because that is your closing speed directly towards the patrol.

[scumdog]

No - that's not what I'm saying. I'm sure that the patrol vehicle display is from the microwave unit, not a mechanical input. What I'm saying is that your relative speed towards the patrol is what is displayed. That is to say if travelling at a direction of 45 deg to the patrol doing 100km/h it will only register 71km/h (cosine effect) because that is your closing speed directly towards the patrol.

We're well aware of the cosine effect.

What it means then is that should you get 'pinged' coming around the corner towards the cop and are exceeding the speed limit then the reading MAY be slower than your actual speed, ergo you're on a 'win' in that situation since your ticket will be for a lesser speed than you were actually doing.

[Max Preload]

We're well aware of the cosine effect.

Clearly not everyone is. You assume to much.

[swbarnett]

No - that's not what I'm saying. I'm sure that the patrol vehicle display is from the microwave unit, not a mechanical input. What I'm saying is that your relative speed towards the patrol is what is displayed. That is to say if travelling at a direction of 45 deg to the patrol doing 100km/h it will only register 71km/h (cosine effect) because that is your closing speed directly towards the patrol.

Now that I rethink it your original statement can be read this way and that's probably what you meant. All make sense now. Thanks.

[Patrick]

I suddenly have so much more respect for meter maids.

Nah, they hated that and came back as HP... with a vengance...