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## Main Question or Discussion Point

Hi,

I am interested in using an accelerometer to calculate the speed of a car. The accelerometer is a triaxial one and gives 3 values of acceleration; x y and z. These can be assumed to be accurate as i have already worked on the calibration of these values so that they come out in gs. Is there a way to calculate the acceleration of the device independent of its alignment to the motion of acceleration?

For example, the accelerometer would be mounted to the dashboard of the car, but as the car accelerates the rear axle of the car dips and therefore the angle of the vector has changed. This is fine to calculate, if it werent for gravity. I cant understand how to remove the acceleration due to gravity when the exact alignment of the sensor is un known. Does anyone have any ideas?

I am interested in using an accelerometer to calculate the speed of a car. The accelerometer is a triaxial one and gives 3 values of acceleration; x y and z. These can be assumed to be accurate as i have already worked on the calibration of these values so that they come out in gs. Is there a way to calculate the acceleration of the device independent of its alignment to the motion of acceleration?

For example, the accelerometer would be mounted to the dashboard of the car, but as the car accelerates the rear axle of the car dips and therefore the angle of the vector has changed. This is fine to calculate, if it werent for gravity. I cant understand how to remove the acceleration due to gravity when the exact alignment of the sensor is un known. Does anyone have any ideas?