What it means
A traditional Doppler radar measures speed but not position, so with several vehicles in view it can be hard to tell which one was speeding. A 4D imaging radar measures speed, distance, angle and elevation for many targets at once, so each speed can be tied to a lane and a vehicle. The camera then supplies the plate read and the image.
How it applies in India
The Department of Consumer Affairs notified rules for radar equipment for the measurement of vehicle speed under the Legal Metrology (General) Rules, 2011, in force from 1 July 2025. PIB's release says all radar-based speed measurement equipment must be verified and stamped by Legal Metrology authorities, and that the rules draw on the international standard OIML R 91. Rule 167A of the Central Motor Vehicles Rules covers the use of speed cameras and speed guns for challans. For a project, ask for the Legal Metrology stamping, test reports at the road's speed range, and the lane attribution method. Stellarview VSDS pairs a 4D Doppler radar with a Recon camera.