Time-of-Flight (LIDAR)
Definition
A measurement principle where the device emits short laser pulses and times how long each pulse takes to return. Multiple pulses over a fraction of a second give distance vs time, and the slope is speed.
- Principle
- Timing how long each laser pulse takes to return
- Output
- Distance versus time from multiple pulses per fraction of a second
- Derived value
- Speed, from the slope of distance over time
- Domain
- Traffic speed enforcement devices
Common questions
How does LIDAR speed measurement differ from radar?+
Radar measures speed directly from the Doppler shift of a reflected radio wave, while LIDAR calculates speed indirectly from a series of distance measurements over time. LIDAR's tighter beam also lets an operator target one vehicle more precisely in traffic.
What can make a LIDAR speed reading unreliable in court?+
Common challenges include operator aiming error at long range where the beam has widened enough to catch more than one vehicle, inadequate device calibration records, and unverified line-of-sight obstructions during the measurement window.
Related terms
- ANPR
- Automatic Number Plate Recognition. A camera plus OCR pipeline that reads vehicle number plates at speed and logs the plate, timestamp, and...
- Calibration Cycle
- The periodic re-certification of a speed-measurement device against a traceable reference, usually annually for radar guns and every six months for LIDAR....
- Cosine Error
- The under-reading of true speed that occurs when the radar or LIDAR beam is not perfectly aligned with the vehicle's direction of...
- Doppler Effect
- The change in observed frequency when the source and the observer move relative to each other. A radar gun emits a known...
- FASTag-ANPR Fusion
- Indian highway tolling pairs RFID FASTag reads with ANPR cameras at every electronic toll gantry, creating a national vehicle-position log that investigators...