What is actually on the car
Modern driver assistance is a set of separate sensors, each with its own aim and its own calibration requirement.
The forward camera. Behind the windshield, near the mirror. Reads lane markings, traffic signs, vehicles and pedestrians. Drives lane keeping, automatic emergency braking and traffic sign recognition.
The forward radar. Usually behind the grille or in the bumper. Measures distance and closing speed. Drives adaptive cruise and much of the braking intervention.
Blind-spot radars. In the rear bumper corners, one each side.
Surround-view cameras. In the grille, the tailgate and both mirrors.
Ultrasonic sensors. In the bumpers, for parking.
The steering angle sensor. In the steering column. Not a driver-assistance sensor exactly, but every system that predicts where the car is going reads it.
What puts one out
- Windshield replacement. The camera is mounted to a bracket bonded to the glass. New glass means a new bracket position, measured in fractions of a millimetre.
- Front bumper removal or replacement. The radar is behind it, and its bracket goes with it.
- Rear bumper work. Blind-spot radars.
- Mirror replacement. Surround-view and, on some vehicles, blind-spot cameras.
- Suspension work that changes ride height. Springs, struts, air suspension, a levelling kit, or a load-carrying conversion. The sensors aim relative to the road, and the vehicle's attitude has changed.
- Wheel alignment. Thrust angle is the reference for anything predicting the path ahead.
- Any collision, however light, in the area of a sensor.
- Sometimes a battery replacement or a module software update, depending on the manufacturer.
Static and dynamic
Static calibration happens in a bay with the vehicle stationary. Targets — printed patterns on frames — are set at manufacturer-specified distances, heights and lateral offsets from the vehicle's centreline, and the scan tool runs a routine while the camera or radar looks at them.
It has real requirements and they are not suggestions:
- A level floor, within a tolerance the manufacturer specifies. Not "flat enough".
- Space around the vehicle, often several metres in front and to the sides.
- Controlled lighting, with no strong reflections and no direct sunlight through the target area.
- Correct tyre pressures, correct ride height, and the vehicle unloaded — no tools in the boot, and sometimes a specified fuel level.
- The vehicle's thrust angle known, which usually means an alignment first.
Dynamic calibration is a drive. The scan tool puts the module into a learn mode and the vehicle is driven at a specified speed range, on a road with clear lane markings, for a set distance or until the module reports completion.
Its requirements are about the road: clear markings, adequate light, no heavy rain, no heavy traffic, and enough continuous distance at the specified speed.
Many vehicles need both, in a specified order. Skipping the static half because the dynamic half completed is not a shortcut; they calibrate different things.
Why an aimed camera matters more than it sounds
A camera looking one degree low is not obviously wrong. The picture is sharp, the lane markings are visible, and nothing about it looks like a fault.
But the system converts image position into distance, and it does that using a fixed assumption about where the camera is pointing. One degree of error at a hundred metres is roughly 1.7 metres. That is the difference between a vehicle in your lane and a vehicle in the next one.
The consequence is not usually a crash. It is a system that brakes for a car that is not there, or fails to see one that is, and an owner who turns the whole thing off because it is unreliable.
Glass, and the part that surprises people
The forward camera looks through the windshield, so the glass is part of the optical path. What matters is not only that the glass is the right shape:
- The bracket must be the correct one, in the correct position, bonded to the correct tolerance.
- The optical wedge and thickness in the camera's viewing area affect refraction.
- Acoustic and infrared-reflective interlayers and heating elements can sit in the viewing area, and there is usually a specified clear zone.
- Distortion within the automotive standard is still distortion, and a camera calibrated on one piece of glass may not calibrate on another that is nominally equivalent.
Glass supplied for a vehicle with a camera should be specified for the camera, not merely for the vehicle.
What a proper job looks like
- Pre-scan the vehicle and record every module and every stored code before any work begins.
- Carry out the repair.
- Confirm the prerequisites: tyre pressures, ride height, fuel and load state, alignment and thrust angle.
- Run the manufacturer's procedure — static, dynamic, or both in the specified order.
- Post-scan and record. Compare against the pre-scan.
- Road test, and confirm the system behaves.
- Document what was calibrated, by whom, and against which procedure.
That documentation is the part garages skip and the part that matters if anything is ever questioned. A calibration nobody recorded is a calibration nobody can prove happened.
Questions people ask
- No warning light came on. Do I still need calibration?
- Yes. A camera aimed a degree low still produces a valid picture and the system has no way to know the picture is wrong. At a hundred metres, one degree is nearly two metres of lateral error. The absence of a fault code is not evidence of correct aim.
- Does a wheel alignment need an ADAS calibration?
- If the thrust angle changed, yes for anything that references the vehicle's direction of travel — which includes the forward camera and radar on most systems, and the steering angle sensor on all of them. An alignment that only adjusted toe within a small range is a judgement call; the manufacturer's procedure decides it, not the technician's preference.
- Can an aftermarket windshield stop a calibration from completing?
- It can. The camera looks through the glass, and the optical properties of the glass in that area — thickness, wedge angle, distortion, and any coating or heating element — are part of the system. Glass that is dimensionally correct but optically different can fail calibration with no other fault present.