Patent ID: 8666694

Claim:
An inertial device for determining an initial condition inertial reference frame for a body, the inertial device comprising: at least one inertial measurement unit (IMU) configured to provide rotation information along at least one axis; one or more processing devices coupled to the at least one IMU; one or more memory devices coupled to the one or more processing devices, wherein the one or more memory devices include instructions which, when executed by the one or more memory devices, cause the one or more processing devices to: receive rotation information from the IMU along at least one axis, the rotation information starting at a first time; estimate a rate profile for the body from a second time that is prior to the first time, to the first time, based on a model spin-up characteristic for the body corresponding to a time prior to the first time through at least the first time; integrate across the rate profile to determine an accumulated rotational angle for the body from the second time to the first time; and send an indication of the accumulated rotation angle for later use.