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Police officer questions
 
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PAUPERSUM
Peon
Dances With
Caltrops

P: 11/28/2023 14:42 EST
E: 11/28/2023 14:48 EST
    Consider how the following is an accurate observation: when a cop scans a vehicle with a speedometer there is no ruler (or some kind of line gauge) in between this device and the vehicle of theoretical measurement. PTA, what's your input? Does this fact leave room for uncertainty? Room for error...  
LuCuS
Super Regular
Scout Pole
Dancer

P: 11/28/2023 14:52 EST
    If it`s a laser gun you don`t stand a chance as they have all the metrics... distance and speed so it`s really hard to fight in court. Plus very often they take more than one reading.  
XenOz3r0xT
Super Regular
Shotgun Quick
Draw

P: 11/28/2023 15:37 EST
E: 11/28/2023 15:38 EST
   
PAUPERSUM wrote:
Consider how the following is an accurate observation: when a cop scans a vehicle with a speedometer there is no ruler (or some kind of line gauge) in between this device and the vehicle of theoretical measurement. PTA, what's your input? Does this fact leave room for uncertainty? Room for error...
This is the book I used for modern physics where we covered stuff like this. Your answer is in the first few chapters.
https://a.co/d/1LbXT6N
  
PAUPERSUM
Peon
Dances With
Caltrops

P: 11/28/2023 16:49 EST
E: 11/28/2023 17:21 EST
    I'll explore different libraries for this book, since I will not likely be purchasing anything today. Generally, I understand my own answers, just not decisive about every pertinent theoretical worldview at the moment. But, for now I'd conclude that we acknowledge room-for-error due to the type of technology in use. And this worldview applies to any internal speedometer of the vehicle itself, although such measurement could be more reliable than the police scanner, because its calibration renders the spatiality factor possibly less relevant. Maybe this is just my opinion for now.

Any kind of speedometer is more than likely based on some type of mathematical approach of breaking down numbers into even values. For example, 60mph (sixty miles per hour) is the aggregation of '1 mile per minute,' but multiplied by sixty. When the new-world device says you're traveling 70mph or something else (whatever your speed is), you really haven't covered the real distance in miles at the moment. Neither has one hour completed.
  
Ignorant_Florist
Daycare Manager
Pipebomb Monkey

P: 11/28/2023 17:37 EST
    All I'm going to say about this topic is this:

Lasers travel at the speed of light, which is a constant. The value of the vehicle being measured in MPH from a source traveling at the speed of light (when properly calibrated) can easily judge your speed to the point of being very difficult to argue in court.

TL:DR - Science, Bitch!
  
PAUPERSUM
Peon
Dances With
Caltrops

P: 11/28/2023 19:38 EST
E: 11/28/2023 19:53 EST
    The speed of light cannot predict the future. It cannot reveal the science of traveling at 100mph while you have been driving for less time and distance. How a device scans for the vehicle is one thing; but how the aggregate math is compounded is another. One other problem is the angle and perceived distance, and some other kind of environmental factor.

Now, an actual speedometer is an attempt at ascertaining milliseconds and millimeters. Then the numbers are multiplied until one hour is totaled out. Measuring distance in the context of a sun-dial makes more viable sense.

  
Ignorant_Florist
Daycare Manager
Pipebomb Monkey

P: 11/28/2023 20:43 EST
    Do you even Math?  
Prelude to Agony
Super Regular
Sniper Harassment
Duty

P: 11/28/2023 20:53 EST
   
PAUPERSUM wrote:
Consider how the following is an accurate observation: when a cop scans a vehicle with a speedometer there is no ruler (or some kind of line gauge) in between this device and the vehicle of theoretical measurement. PTA, what's your input? Does this fact leave room for uncertainty? Room for error...
Laser measures time and distance of the beam to go out and return to the device to calculate speed. You verify it at the beginning and ending of your shift, or the term you're using it. It's always used stationary. The best part of Lidar is you know with certainty which vehicle you're measuring.

Straight on is best, and there's a formula for how the speed is affected as you gravitate away from zero. IIRC, since it's been years since I've used one, it's to the benefit of the driver and will show a slower speed the wider the angle.

Radar also measures the time it takes the signal to bounce off of the vehicle and return to the device to calculate speed. It's best in stationary mode, but works moving and even same direction. It is also verified at the beginning and ending of the shift. These devices are verified using tuning forks (gauged for various speeds) and also in the moving mode, verifying the patrol speed to the speedometer in the vehicle, which is calibrated. There is an allowable 1 to 2 mph variance allowed in patrol speed, which can be larger at higher speed.

Verification of the calibrated speedometer is done using Lidar, but also using a time/distance method. Patrol moves at a constant speed, the time is started when it crosses the start line and stopped when it crosses the finish line of a known distance, usually 1/4 mile. Then math.

So, in essence, if I'm working moving radar, as long as the patrol window speed and the speedometer match, or is within tolerance, then the target speed is confirmed. In stationary mode, the target speed is the target speed, nothing more to say.

Stationary mode is nearly impossible to beat in court. Lidar is 100%, though the distance of reading can be argued as to the accuracy of the speed. 1000 feet or less is golden, anything over 1/4 mile is sketch from a court standpoint.

Be advised, changing anything from stock on your vehicle, mostly tire size, can affect the speed of your vehicle versus what your speedo says by +/- 5mph or more.

Does that answer your query?

  
PAUPERSUM
Peon
Dances With
Caltrops

P: 11/30/2023 15:04 EST
E: 11/30/2023 15:14 EST
    Well, it was your answer, which is something I requested. Nevertheless, are you telling me the laser measures time and distance, or is it the device generating the hypothetical laser that supposedly computes the measurement? I mean, human beings cannot read light or some kind of laser the same way a ruler or line-gauge is perceived. If you lay out measuring tape you can ascertain the measurement without any electronics. Just a thought...  
gg#4
Super Regular
Killer Scout

P: 11/30/2023 15:32 EST
E: 11/30/2023 15:43 EST
   
Prelude to Agony wrote:
Be advised, changing anything from stock on your vehicle, mostly tire size, can affect the speed of your vehicle versus what your speedo says by +/- 5mph or more.
Damn I never actually thought about that.

My car was designed for a 305/35 and I have 305/30s on them. So im actually going slower than my speedometer reads.

Cool calculator

https://tiresize.com/comparison/
So if I am going 90mph I am really going 86.1 if I compare 305/35-r19 to 305/30-r19
  
Prelude to Agony
Super Regular
Sniper Harassment
Duty

P: 11/30/2023 18:39 EST
    Yep...I have had peeps tell me their speed versus the speed I had them at and I always ask if they changed anything. Almost always it's the tires.   
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