A method for calibrating a pressure-sensing altitude sensor of an aircraft while the aircraft is in flight. The method includes the steps of obtaining a set of reference atmospheric pressures as a function of height above a base station by affixing a reference pressure sensor to a balloon. As the balloon is released into the atmosphere, the reference sensor continuously measures the atmospheric pressures and transmits the data back to the base station while a ground-based radar disposed adjacent the base station measures the height of the balloon. An aircraft flying in a vicinity of the base station can calibrate its pressure-sensing altitude sensors by measuring the atmospheric pressure outside the aircraft and its geometric height relative to the base station and then comparing the pressure measurements with corresponding reference pressure values at a geometric height that is substantially that same as the geometric height of the aircraft.
CROSS REFERENCE
This application claims the benefit of a prior-filed co-pending provisional. application, Ser. No. 60/042,422, that was filed on Mar. 27, 1997.
Some embodiments of the invention provide a location-determination system that includes a number of transmitters and at least one receiver. Based on a reference signal received by the receiver, this location-determination system identifies an estimated location of the receiver within a region. In some embodiments, the system selects one or more locations within the region. For each particular selected location, the system calculates a metric value that quantifies the similarity between the received signal and the signal that the receiver could expect to receive at the particular location, in the absence or presence of interference. Based on the calculated metric value or values, the system identifies the estimated location of the receiver.
Disclosed is a communication device and method for estimating a more accurate vertical position or altitude of a communication device using atmospheric pressure measurements. In one embodiment, a first communication device comprises a pressure sensor for measuring local atmospheric pressure at the first communication device and a transceiver for communicating with a second communication device, wherein the transceiver may be operable to receive barometric calibration information for calibrating a local atmospheric pressure measured at the first communication device and/or to transmit the measured local atmospheric pressure to the second communication device. The first communication device may further comprise a processor for estimating an altitude using the measured local atmospheric pressure and received barometric calibration information.
A turbulence analysis system comprises a communication interface and a processing system. The communication interface receives time variance metrics for a plurality of satellite signals. The time variance metrics correspond to variances in signal transfer times for individual satellite signals. The processing system determines position metrics for the individual satellite signals. The position metrics correspond to geometric signal paths in a three-dimensional area for the individual satellite signals. The processing system processes the position metrics and the time variance metrics for the satellite signals to allocate atmospheric turbulence values to the three-dimensional area to produce an atmospheric turbulence map indicating the atmospheric turbulence values in the three dimensional area. The communication interface transfers the atmospheric turbulence map.
A portable, handheld electronic navigation device includes an altimeter and a GPS unit. An internal memory stores cartographic data, for displaying the cartographic data on a display of the navigation device. Accordingly, the device is capable of displaying cartographic data surrounding a location of the unit as determined by GPS and altitude information as determined by the barometric altimeter and GPS. The device provides an enhancement of the calibration and hence the accuracy of barometric altimeter measurements with the aid of derived altitudes from a GPS. The device is able to determine the need for calibration and perform the subsequent computations necessary to facilitate the calibration. Furthermore, the device is able to determine a correction quantity that should be applied to barometric altitude readings, thereby allowing the device to be calibrated while in motion. Both of these features ultimately result in a more accurate determination of altitude. In accordance with an aspect of the invention, the altimeter of the navigation device may be calibrated with altitude information entered by a user, with altitude information obtained from the cartographic, with altitude information derived from GPS or with any combinations thereof.
A portable, handheld electronic navigation device includes an altimeter and a GPS unit. An internal memory stores cartographic data, for displaying the cartographic data on a display of the navigation device. Accordingly, the device is capable of displaying cartographic data surrounding a location of the unit as determined by GPS and altitude information as determined by the barometric altimeter and GPS. The device provides an enhancement of the calibration and hence the accuracy of barometric altimeter measurements with the aid of derived altitudes from a GPS. The device is able to determine the need for calibration and perform the subsequent computations necessary to facilitate the calibration. Furthermore, the device is able to determine a correction quantity that should be applied to barometric altitude readings, thereby allowing the device to be calibrated while in motion. Both of these features ultimately result in a more accurate determination of altitude. In accordance with an aspect of the invention, the altimeter of the navigation device may be calibrated with altitude information entered by a user, with altitude information obtained from the cartographic, with altitude information derived from GPS or with any combinations thereof.
