Hi Ugur,
The imuSensor, gpsSensor, and insSensor objects are stochastic noise sensor models. This means that they use random processes to approximate the noise in various sensors. The level of acceptable approximation depends on your use case.
For the imuSensor object, there is a loadparams function that allows you to set the sensor parameters based on a JSON-file. There is an example JSON-file with a generic low-cost 6-axis and 9-axis IMU.
For the gpsSensor and insSensor objects, the parameters can be set based on your specific GPS and INS datasheets.
Thanks,
Ryan