A system for determining a combined velocity rotation compensation and sculling compensation in an inertial navigation system includes: gyroscopes configured to provide a measured angular rotation rate with components from three orthogonal axes; accelerometers configured to provide a measured specific force with components from three orthogonal axes; and a processor configured to calculate a first combined velocity rotation compensation and sculling compensation at a single computational rate, the processor configured to: calculate a first cross product of an instantaneous angular rotation rate and a change in the measured specific force during a first interval; and sum the first cross product with a second cross product of a fraction of the change in the specific force during the second interval and the change in the measured angular rate during the first interval; where the first and second intervals are each one cycle of the single computational rate.