A seismic node for collecting seismic data, the seismic node including a base configured to define a chamber having an open face; a main electronic board having a processor, the main electronic board being placed inside the chamber; a battery pack configured to supply electrical power to the main electronic board and placed inside the chamber; and a digital cover that attaches to the open side of the base to seal the chamber, and a sensor device located inside the chamber and attached to a wall of the base to form a digital field unit, or an analog cover that attaches to the open side of the base to seal the chamber, and an analog sensor electrically attached to the analog cover to form an analog field unit.

Provided herein is a method for separating Loran sky and ground waves based on a Levenberg-Marquart algorithm, including: (1) collecting a plurality of Loran sky-ground wave signals followed by normalization to obtain a normalized signal; (2) preprocessing the normalized signal by inverse Fourier transform method to obtain an initialization parameter; (3) establishing a mathematical model for the Loran sky-ground wave signals in time domain; and (4) solving parameters of the mathematical model using the Levenberg-Marquart algorithm to separate the Loran sky and ground waves.

Provided herein is a method for separating Loran sky and ground waves based on a Levenberg-Marquart algorithm, including: (1) collecting a plurality of Loran sky-ground wave signals followed by normalization to obtain a normalized signal; (2) preprocessing the normalized signal by inverse Fourier transform method to obtain an initialization parameter; (3) establishing a mathematical model for the Loran sky-ground wave signals in time domain; and (4) solving parameters of the mathematical model using the Levenberg-Marquart algorithm to separate the Loran sky and ground waves.

A method for the determining a position of at least one measurement object equipped with a mobile station having a receiver includes employing at least four reference objects having a base station and a transmitter, wherein a first reference object of the at least four reference objects has a mobile station with a receiver and simultaneously acts as a measurement object. The base station and the mobile station are structurally combined. The reference objects initially have a known position that can change. The transmitters of the base stations transmit signals and the mobile stations receive signals. The method additionally includes emitting, by at least two transmitters of base stations, periodic signals of different frequencies at mutually defined time intervals, wherein these frequencies are closely adjacent.

A method for the determining a position of at least one measurement object equipped with a mobile station having a receiver includes employing at least four reference objects having a base station and a transmitter, wherein a first reference object of the at least four reference objects has a mobile station with a receiver and simultaneously acts as a measurement object. The base station and the mobile station are structurally combined. The reference objects initially have a known position that can change. The transmitters of the base stations transmit signals and the mobile stations receive signals. The method additionally includes emitting, by at least two transmitters of base stations, periodic signals of different frequencies at mutually defined time intervals, wherein these frequencies are closely adjacent.

The modulation includes in amplifying the microwave signal phase shifted by a given angle into a first sinusoidal signal, in order to obtain a first amplified signal; and in amplifying the microwave signal phase shifted by the given angle increased by into a second sinusoidal signal phase shifted by with respect to the first signal, in order to obtain a second amplified signal phase shifted by with respect to the first amplified signal; the modulated microwave signal being the sum of the first amplified signal and the second amplified signal.

The modulation includes in amplifying the microwave signal phase shifted by a given angle into a first sinusoidal signal, in order to obtain a first amplified signal; and in amplifying the microwave signal phase shifted by the given angle increased by into a second sinusoidal signal phase shifted by with respect to the first signal, in order to obtain a second amplified signal phase shifted by with respect to the first amplified signal; the modulated microwave signal being the sum of the first amplified signal and the second amplified signal.

The modulation includes in amplifying the microwave signal phase shifted by a given angle into a first sinusoidal signal, in order to obtain a first amplified signal; and in amplifying the microwave signal phase shifted by the given angle increased by into a second sinusoidal signal phase shifted by with respect to the first signal, in order to obtain a second amplified signal phase shifted by with respect to the first amplified signal; the modulated microwave signal being the sum of the first amplified signal and the second amplified signal.

The modulation includes in amplifying the microwave signal phase shifted by a given angle into a first sinusoidal signal, in order to obtain a first amplified signal; and in amplifying the microwave signal phase shifted by the given angle increased by into a second sinusoidal signal phase shifted by with respect to the first signal, in order to obtain a second amplified signal phase shifted by with respect to the first amplified signal; the modulated microwave signal being the sum of the first amplified signal and the second amplified signal.

A method for the determining a position of at least one measurement object equipped with a mobile station having a receiver includes employing at least four reference objects having a base station and a transmitter, wherein a first reference object of the at least four reference objects has a mobile station with a receiver and simultaneously acts as a measurement object. The base station and the mobile station are structurally combined. The reference objects initially have a known position that can change. The transmitters of the base stations transmit signals and the mobile stations receive signals. The method additionally includes emitting, by at least two transmitters of base stations, periodic signals of different frequencies at mutually defined time intervals, wherein these frequencies are closely adjacent.