LiDaR accuracy.

Gotubabe · Guest

I understand that LiDAR is supposed to be very accurate. But how accurate are mulitiple guns if used side-by-side? Can one gun read a beam that originated from the other? Is it possible for the gun to KNOW that the beam it receives is the beam that it produced if there are several guns being used simultaneously? I don't know the technology backwards-and-forwards but I don't see how a "pulse" of light can be uniquely 'tagged' or ID'd. Unless each beam's pulse IS infact unique.
Is this the case or can one gun 'confuse' the other?

A knowledgable response is greatly appreciated.

CopRadar · Joined: 27 Jun 2006 Posts: 12

If 2 or more lidar guns transmit at the same rate (pulses per second) and have the same pulse width, and are both pointed in roughly the same direction the lidars WILL interfer with each other.

Pulse rate and width vary from model to model. Sometimes the same model may be programmed with a different pulse rate/width from the factroy installed version.

A lidar looks for a specific pulse rate (pulses per second) and pulse width, however the lidar will have to process out pulse echoes that do not match the expected parameters.

If the pulse rate and/or pulse width are different the lidars may or may not interfer with each other. Basically sometimes the lidars will interfer and sometimes they will not. Sometimes false speed reading can be displayed depending on a number of variables. In any case both lidars maximum detection range will be reduced.
_________________
Best Regards,
Donald Sawicki
Radar Specialist
www.radarguns.com

Gotubabe · Guest

Thanks for the reply.

To clarify my question: Can/will a pulse from one gun return to another and display an actual speed value or would it be an error or nothing at all.

I guess the idea sistuation would be a speed enforcement where two or more officers are side-by-side, targeting oncoming vehicles in lanes side-by-side.

Also on a side note: I understand that the 'cone'/beam can be up to 18" in diameter. If a motorcycle which is less than 16" wide is targeted; can the pulse 'bleed' past the motorcycle (on either side), hit the headlight of a following car behind it and return to the gun and track the speed of the car behind the motorcycle? (I know...) But Is this possible?

Thanks again for your response.

CopRadar · Joined: 27 Jun 2006 Posts: 12

Lidars (depending on model) must receive (and transmit) tens to several hundreds of pulses to make ONE speed measurement. A few stray pulses will make little if any difference.

Two lidars operating next to each other trying to measure targets in different traffic lanes at the same time could (but not always) produce a false speed reading. The circumstances to predict a false speed reading involve a number of variables, not all variables are known and some change with situation (such as exact time each lidar transmits, sample start/stop periods, range of targets, etc.).

Two lidars should not be operating next to each due to the uncertainty of the accuracy and reliability of any speed measurements.

Lidar beam coverage depends on beamwidth and target range. Most lidars have a beamwidth between 3 and 4 milliradians (0.17 to 0.23 degrees). A 16 inch beam spread would occur at a range of 444 feet for a 3 mR beam and 333 feet for a 4 mR beam.

Yes is is possible for a lidar (or microwave radar) to measure the speed of a larger vehicle behind (more distant from lidar) than a closer smaller vehicle.
_________________
Best Regards,
Donald Sawicki
Radar Specialist
www.radarguns.com