The "camera vs ultrasonic" debate is the single most common question we get from facility managers evaluating a Parking Guidance System. Both work. Both have been deployed at scale. The right choice depends on three things: ceiling height, lighting variability, and what other use-cases you want to unlock from the same sensor.
Ultrasonic sensors are the workhorse of indoor PGS. They're cheap per-bay, they don't care about light, and they survive in dusty, exhaust-heavy environments. They're also dead simple — emit a ping, measure return time, infer presence. That simplicity is also their weakness: they only know whether a bay is occupied. They can't tell you which car, when it arrived, or whether it has a valid permit.
Camera-based bay monitoring trades cost for context. Each camera covers 4–8 bays and runs on-device computer vision to detect occupancy. The same camera can also read license plates (ANPR), flag double-parking, support automated valet routing, and feed analytics about dwell time. The price-per-bay is higher, and the system is more sensitive to lighting changes — which is why most rollouts blend both sensor types.
Our standard recommendation: ultrasonic for tier-1 lots where you just need occupancy guidance, camera-based for anywhere you also want a security or analytics outcome.