The shipboard wave measurement system (SWMS) makes measurements as a function of time of vehicle position, range from the vehicle to the water's surface, and vehicle heave, pitch and roll to compute the height, direction, period and wavelength of the principal ocean wave component. Since the vehicle is moving, the wave heights measured are at different spatial locations, as well as at different times, and the observed wave height signal is Doppler shifted. The SWMS is composed of a positioning device, a timing device, a wave height estimator (WHE), a Doppler Integrator (DI) and a computer. The positioning device measures the vehicle's position, the timing device provides accurate time referencing for the vehicle position and wave height measurements. The wave height estimator measures range to the water's surface from the vehicle and vehicle vertical acceleration, pitch and roll and generates wave height at specific instants of time. The Doppler integrator receives the time referenced wave height signal from storage and generates the frequency and height of the principal wave component, both as a function of time. Wave direction, period and wavelength are determined from the wave frequency and vehicle position data using a least-squares approach.
A method for determining heave and heave rate for a vessel is described. The vessel includes an inertial navigation system (INS), and sensors for the INS being located at a point A of the vessel, the vessel having a zero heave reference point B, and the described method provides heave and heave rate at a point C of the vessel. The method includes determining reference coordinates for points A, B, and C of the vessel, generating a velocity signal representative of a velocity at a point on the vessel, generating a heave rate signal based upon the velocity signal, and generating a heave based upon the heave rate signal.
An altitude measuring system and method for aircraft is provided. The altitude measuring system includes altitude sensors for providing data to an altitude processing unit. The altitude processing unit spatially averages each output to determine a mean altitude. Pitch and roll are accounted for by correction. A method of determining aircraft altitude from a plurality of altitude sensors includes receiving altitude sensor data from each sensor and spatially averaging the altitude sensor outputs to determine aircraft altitude. A method of estimating the maximum height of an ocean surface includes receiving a plurality of altitude sensor data and determining a mathematical description of the ocean surface from the sensor data. The maximum probable wave height of the ocean surface is estimated from the mathematical description. From the maximum wave height, a cruise altitude may be determined.
