Hi Maybe my math/stat is very poor. I'm having trouble manipulating the standard deviation. Here's the thing. I have radar mounted on a car. For each detection, the radar returns these variables. - relative distance between the object/host vehicle in forward direction (in vehicle body-fixed coordinates) - standard deviation of the relative forward distance - relative distance between the object/host vehicle in left/right direction (in vehicle body-fixed coordinates) - standard deviation of the relative left/right distance I'm trying to do coordinate transform of the above data, so that I get relative distance/standard deviation in global coordinates (North, South, East, West) Distance is easy since it only requires to rotate the axis by the amount of angle between the vehicle body-fixed axis and the global axis. How about standard deviation? How do I transform the standard deviation from the vehicle body-fixed axis to global axis?