In non-limiting examples of the present disclosure, systems and methods for dynamically updating contour maps are provided. A first water level for a body of water may be determined by a computing device. A location within the body of water may be identified. A second water level relating to the identified location within the body of water may be determined, and the second water level and the first water level may be compared. Upon comparing the first and second water levels, a contour map for the body of water may be automatically updated.

Disclosed are a method and system for evaluating sonar self-noise at a ship design stage. The method includes: building a ship structure full-scale geometric simulation model; acquiring loss factors and sonar transducer space outfitting acoustic absorption coefficient material parameters; acquiring mechanical excitation, hydrodynamic excitation, and propeller excitation; inputting the loss factors and the sonar transducer space outfitting acoustic absorption coefficient material parameters into an established statistical energy evaluation model, and applying a mechanical excitation to a face plate of foundation of the built ship structure full-scale geometric simulation model, applying a hydrodynamic excitation to the surface of a ship hull, and applying a propeller excitation to a stern shaft to perform calculation of sonar self-noise of a ship to obtain total spectral density level of the sonar self-noise; and evaluating spectral density level calculation results by index requirements. The method is applicable in risk evaluation of sonar self-noise indexes.

Disclosed are a method and system for evaluating sonar self-noise at a ship design stage. The method includes: building a ship structure full-scale geometric simulation model; acquiring loss factors and sonar transducer space outfitting acoustic absorption coefficient material parameters; acquiring mechanical excitation, hydrodynamic excitation, and propeller excitation; inputting the loss factors and the sonar transducer space outfitting acoustic absorption coefficient material parameters into an established statistical energy evaluation model, and applying a mechanical excitation to a face plate of foundation of the built ship structure full-scale geometric simulation model, applying a hydrodynamic excitation to the surface of a ship hull, and applying a propeller excitation to a stern shaft to perform calculation of sonar self-noise of a ship to obtain total spectral density level of the sonar self-noise; and evaluating spectral density level calculation results by index requirements. The method is applicable in risk evaluation of sonar self-noise indexes.

A method for estimating a range of a moving target includes emitting, from a target, a first ultrasound signal T, wherein the first ultrasound signal T is generated based on a first differential Zadoff-Chu sequence x; receiving, at a receiver, a second ultrasound signal R, which corresponds to the first ultrasound signal T, wherein the second ultrasound signal R includes a second differential Zadoff-Chu sequence y; applying a maximum likelihood estimator to the first ultrasound signal T and the second ultrasound signal R to calculate an initial time of flight estimate tau.sub.corr; and calculating an initial range estimate d.sub.corr of the target by multiplying the initial time of flight estimate tau.sub.corr with a speed of sound c. A differential Zadoff-Chu sequence is different from a Zadoff-Chu sequence.

Embodiments of the present invention provide a navigation system which, on the one hand, is arranged on sides of the underwater vehicle/AUV and, on the other hand, includes a surface transmitter as a counterpart. The two units communicate with each other such that the surface transmitter emits its signal directed to the position of the underwater vehicle and/or that the surface transmitter follows the underwater vehicle to improve the position determination capability.

Embodiments of the present invention provide a navigation system which, on the one hand, is arranged on sides of the underwater vehicle/AUV and, on the other hand, includes a surface transmitter as a counterpart. The two units communicate with each other such that the surface transmitter emits its signal directed to the position of the underwater vehicle and/or that the surface transmitter follows the underwater vehicle to improve the position determination capability.

Methods and systems for the efficient determination of the direction of multiple signal sources in both near and far field using hierarchical combinations of sets of raw input signals to convert spatial input to angular output. Each increasing hierarchical combination increases angular resolution, improving image quality with low computational expenditure.

Techniques are described herein for displacing liquid away from a signal path of sonic signals in a signal anemometer. A sonic anemometer may include a membrane positioned between a sonic transducer and the open environment. The membrane may be formed of a hydrophobic material that repels the liquid. The membrane may also include a plurality of pores that impede the flow of liquid through the membrane but enables sonic signals to pass through the membrane. The sonic anemometer may also include a reflector that displaces liquid away from the signal path of the sonic anemometer. The reflector may include one or more pores that wick liquid away from the signal path.

A method for filtering in ranging of a UAV is provided, which is based on a characteristic that velocities of the UAV change continuously during a moving process. A current velocity of the UAV is obtained via seeking difference of distances measured by the sensor, then a variance of continuous velocities is calculated and it is determined whether a current distance is valid according to the variance. The general process of the method is as follows. First, initial distances measured by the sonar sensor are acquired, secondly, it is determined whether a new distance is valid according to the initial distances, if the new distance satisfies a curtain condition, the new distance is considered to be valid and the initial distances are updated; if the new distance does not satisfy the curtain condition, a distance is estimated and used as the current distance and the initial distances are maintained.

A system includes a processor configured to access a train schedule to determine active train crossings along an original route, based on a predicted vehicle-arrival time at a given crossing. The processor is also configured to determine that a driver identity has an avoidance parameter associated therewith and determine a new route avoiding active train crossings, if possible, responsive to the avoidance parameter and determination of at least one active train crossing along the original route.