The present invention discloses a method for determining an inverse of gravity correlation time. During data processing on gravity measurement of moving bases, a gravity anomaly is considered as a stationary random process in a time domain, and is described with a second-order Gauss Markov model, a third-order Gauss Markov model or an m.sup.th-order Gauss Markov model, and the inverse of gravity correlation time is an important parameter of the gravity-anomaly model, and according to a gravity sensor root mean square error, a Global Navigation Satellite System (GNSS) height root mean square error, an a priori gravity root mean square, and a gravity filter cutoff frequency during the gravity measurement of the moving bases, an inverse of gravity correlation time of the second-order, third-order or m.sup.th-order Gauss Markov model is determined. According to the method for determining an inverse of gravity correlation time provided in the present invention, a forward and backward Kalman filter during data processing on gravity measurement of moving bases can be adjusted, to obtain a high-precision and high-wavelength-resolution gravity anomaly value.

An aerial-and-ground data combined gravity conversion methodincludes the following steps: calculate the first estimated ground gravity by the Runge-Kutta format 1, and calculate the first error between the first estimated ground gravity and the measured ground gravity; calculate the second estimated ground gravity by the Runge-Kutta format 2, and calculate the second error between the second estimated ground gravity and the measured ground gravity; and select the smaller one from the first and second errors, use the corresponding Runge-Kutta format as the Runge-Kutta format for gravity conversion, and finish the gravity data conversion using the mentioned Runge-Kutta format.

Exemplary practice of the present invention provides an air vehicle and at least one interferometric double-path fiber optic sensor connected with the air vehicle. Each fiber optic sensor includes a pair of optical fibers, viz., an optical sensing fiber and an optical reference fiber, in a parallel and propinquus relationship. The paired optical fibers of each fiber optic sensor are attached to the air vehicle either (i) circumferentially around the fuselage or (ii) lengthwise along the fuselage or (iii) span-wise along the wings and across the fuselage, and are configured whereby the sensing fiber is exposed to the atmosphere and the reference fiber is not. Each fiber optic sensor senses atmospheric infrasound but does not sense atmospheric wind noise, which is negated by incoherency associated with design lengthiness of the optical fiber pair. Noise and strain due to temperature, vibration, and propulsion are neutralized via interferometric common mode rejection.

Provided is an aircraft 10 which has been configured for conducting airborne gravimetry surveys, comprising a gravimeter 14, a global navigation satellite system (GNSS) receiver 18 arranged in signal communication with the gravimeter 14, as well as a Doppler lidar system 20 arranged in signal communication with the gravimeter 14. The lidar system 20 is configured to determine a vertical velocity of the aircraft 10 at a predetermined time, with a time signal from the GNSS receiver 18 used to operatively synchronise both the gravimeter 14 and lidar system 20 measurements. In this manner, a gravitational acceleration measurement of the gravimeter 14 is differentially isolable from a kinematic acceleration derivable from the synchronous lidar measurement.

Provided is an aircraft 10 which has been configured for conducting airborne gravimetry surveys, comprising a gravimeter 14, a global navigation satellite system (GNSS) receiver 18 arranged in signal communication with the gravimeter 14, as well as a Doppler lidar system 20 arranged in signal communication with the gravimeter 14. The lidar system 20 is configured to determine a vertical velocity of the aircraft 10 at a predetermined time, with a time signal from the GNSS receiver 18 used to operatively synchronise both the gravimeter 14 and lidar system 20 measurements. In this manner, a gravitational acceleration measurement of the gravimeter 14 is differentially isolable from a kinematic acceleration derivable from the synchronous lidar measurement.

A gravimeter for measuring the gravitational field of the Earth without an inertial reference comprises accelerometer pairs disposed on a platform where the sensitive axis of each accelerometer is arranged on the platform to measure plumb gravity. At least one accelerometer pair is spatially configured to define a baseline therebetween. The gravimeter is positioned so that the baseline is maintained parallel to a linear survey path. Each accelerometer outputs a signal representative of the sum total of the accelerations detected, including accelerations due to gravity and kinematic accelerations of the host vehicle and mounting structure. A processor subtracts the accelerometer pair outputs for common-mode rejection determination of a down gravity gradient and combines with a direct plumb gravity measurement to obtain an enhanced gravity data output that is not subject to frequency limits attributed to the performance limitations of inertial reference devices.

A gravimeter for measuring the gravitational field of the Earth without an inertial reference comprises accelerometer pairs disposed on a platform where the sensitive axis of each accelerometer is arranged on the platform to measure plumb gravity. At least one accelerometer pair is spatially configured to define a baseline therebetween. The gravimeter is positioned so that the baseline is maintained parallel to a linear survey path. Each accelerometer outputs a signal representative of the sum total of the accelerations detected, including accelerations due to gravity and kinematic accelerations of the host vehicle and mounting structure. A processor subtracts the accelerometer pair outputs for common-mode rejection determination of a down gravity gradient and combines with a direct plumb gravity measurement to obtain an enhanced gravity data output that is not subject to frequency limits attributed to the performance limitations of inertial reference devices.

Various embodiments described herein provide for a balloon-borne aeroseismometer that can detect infrasonic signals and concurrent vibrations caused by the infrasonic signals. Through a set of motion sensors that can detect acceleration in three planes, the aeroseismometer can determine the direction of vibration and thus determine a travel path of the infrasonic signal relative to the aeroseismometer. The aeroseismometer can also translate the direction of the source from a reference frame of the aeroseismometer to an external reference frame, such as a planetary coordinate system, in order to identify potential locations of a source of the infrasonic signals.

Various embodiments described herein provide for a balloon-borne aeroseismometer that can detect infrasonic signals and concurrent vibrations caused by the infrasonic signals. Through a set of motion sensors that can detect acceleration in three planes, the aeroseismometer can determine the direction of vibration and thus determine a travel path of the infrasonic signal relative to the aeroseismometer. The aeroseismometer can also translate the direction of the source from a reference frame of the aeroseismometer to an external reference frame, such as a planetary coordinate system, in order to identify potential locations of a source of the infrasonic signals.

Examples disclosed herein involve a computing system configured to (i) obtain (a) a first set of sensor data captured by a first sensor system of a first vehicle that indicates the first vehicle's movement and location with a first degree of accuracy and (b) a second set of sensor data captured by a second sensor system of a second vehicle that indicates the second vehicle's movement and location with a second degree of accuracy that differs from the first degree of accuracy, (ii) based on the first set of sensor data, derive a first trajectory for the first vehicle that is defined in terms of a source-agnostic coordinate frame, (iii) based on the second set of sensor data, derive a second trajectory for the second vehicle that is defined in terms of the source-agnostic coordinate frame, and (iv) store the first and second trajectories in a database of source-agnostic trajectories.