I want to use it in my real car for daily use to measure yaw angle when needed.
Is is ok to only calibrate it once at first then use it every day when driving without any problem? if not, how often should I recalibrate it?
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Most accelerometers and gyroscopes need little if any calibration. Consult the manufactures specification sheets. If any calibration is made and correction values found, then it is assumed those values may be used in the future for the same accelerometer / gyroscope.
This analog.com document goes into gyroscope calibration details.
Deriving the angle of the car (the "yaw") at any given moment will likely be problematic. Errors from integrating the gyroscope's axis which is perpendicular to the ground will accumulate over time. Which is the main problem when using dead reckoning.
Consider using a magnetometer & accelerometer along with the gyroscope in order to mitigate the accumulated errors from only using the gyroscope.