To be able to calibrate properly, your calibration station should meet a few requirements. Therefore, Martin arranged an inspection appointment with TÜV-Rheinland to get our calibration station in Gelsenkirchen (Germany) reviewed by a certified inspector. I’m summarizing all the relevant information in this blog article.
Currently, there are no official requirements for a calibration station available from inspection organisations and vehicle manufacturers. Nevertheless, there is an official guideline for a Headlight Alignment Space available in Germany which can be used as a basis. This type of ground condition check for radar and camera calibration is still rarely requested by the inspection organisations, but we recommend doing it.
The requirements for a Headlight Alignment Space are very demanding and ideally suited as a basis for static calibration. However, calibrating ADAS requires more space than adjusting the headlights. The vehicle manufacturers set different distances to the target board as a prerequisite. For example, for VAG vehicles, the distance between the front wheel hub and the target is usually 150 cm, in case of Subaru/Honda/Toyota a distance up to 4 meters is needed. Many calibrations can be performed very well within a room length of 8-10 meters but remember that the length of the vehicle must also be taken into account.
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It is important that the available space is as flat and straight as possible. This can be checked with a ground laser scanner. For this purpose, the values from the official guideline for headlight alignment can be used: The maximum inclination of the installation surface may be +/- 1.5% rectified. In addition, a maximum unevenness of 11 mm is permitted over a length of 8 meters. This means that the height difference may not exceed +/- 5.5 mm between two measuring points. The tolerance of unevenness is staggered and is not constant at 11 mm for all room lengths. The corresponding graduation can be found in the official guideline for headlight alignment.
Our calibration station for a passenger car was measured by TÜV-Rheinland with the help of a floor laser and is approved to be used for ADAS calibration now. The result is recorded in the test report: "This is specifically a set-up area for driver assistance systems. The measurement for the Headlight Alignment Space installation area isn’t necessary." As we aren’t adjusting headlights, the test of the headlight testing machine itself isn’t required. But if you want to calibrate matrix headlights as well, you will need an officially tested Headlight Alignment Space.
How to get the best calibration conditions
To adapt the premises, there are two common solutions: The most flexible solution is the use of track plates that can be adjusted with millimetre precision – regardless of the ground. The slightly more expensive solution is to level the ground itself.
The lighting conditions at the calibration station also play an important role. It is helpful to be able to control the ambient lighting in the room yourself. Fluorescent tubes with older starter systems or poorer quality LED bulbs can cause problems with camera calibration. This is because of our European power grid using 50 hertz alternating voltage.
If the exposure time of the camera deviates greatly from the 50 Hertz, a horizontal flicker occurs in the image acquisition and may lead to incorrect detection of the target. In such cases, you can try to brighten or darken the room so that the camera uses different exposure times. The problem can also be lessened with the use of halogen or incandescent lamps.
Some manufacturers offer mobile calibration systems that enable static calibration directly at the customer's site. However, these systems are intended for fleet customers rather than individual customers, as the local conditions are already known in advance.
What does this mean for you?
Remember that the ground and ambient light play an important role when you calibrate statically. In the case of mobile operations, you should find out the conditions on site first and consider whether a calibration in a controllable environment make more sense.