The Earth's gravitational field has long been used to provide a reference from which to estimate absolute roll and pitch attitudes. Absolute yaw attitudes, or headings, may be derived from the Earth's magnetic field. Conventionally, an accelerometer or fluid level is used to measure instantaneous absolute roll and pitch relative to a gravitationally defined “down” vector, but these types of measurements quickly become noisy and unreliable in the presence of non-gravitational accelerations.
Theoretically, gyroscopes may be used to measure changes in orientation over time, and these changes can be integrated to provide estimations of roll and pitch attitudes, but actual low drift gyroscopes (e.g., that can measure relative orientations accurately over long periods of time) can be extremely expensive, are typically relatively fragile, and can become unreliable when subjected to sustained and/or abrupt non-gravitational accelerations. Thus, there is a need for an improved methodology to provide accurate and reliable attitude estimations using inexpensive sensors, particularly in the context of monitored mobile structures that are subject to sustained and/or abrupt non-gravitational accelerations.