A technique facilitates seismic exploration by identifying time differences between clocks employed during the seismic exploration. According to an embodiment, a seismic signal is output from a source and has an incident wave and a reflected wave. The seismic signal is received by at least one receiver which outputs data to a control system. The control system is employed to compare a symmetry of the propagation of the incident wave and the reflected wave. The symmetry data is then used to determine a temporal change of the time base of the at least one receiver.

A wireless seismic data acquisition unit with a wireless receiver providing access to a common remote time reference shared by wireless seismic data acquisition units in a seismic system. The receiver can replicate local version of remote time epoch to which a seismic sensor analog-to-digital converter is synchronized. The receiver can replicate local version of remote common time reference to time stamp local node events. The receiver can be placed in a low power, non-operational state over periods of time during which the unit continues to record seismic data, thus conserving unit battery power. The system corrects the local time clock based on intermittent access to the common remote time reference. The system corrects the local time clock via a voltage controlled oscillator to account for environmentally induced timing errors.

A system and method for estimating clock drift in underwater instruments is provided. The method can include transmitting a signal from a source to a plurality of underwater receivers or a single receiver. Upon recovery of the underwater receivers, an initial sampling frequency value can be used to generate received data waveforms from data stored on each underwater device. The generated received waveforms can be used to generate a channel estimate for each receiver, and the channel estimates can be used to provide an estimate of the source motion during the transmission. The estimated source motion can then be used to estimate the clock drift.

Method for time drift measurement of at least one slave clock in at least one seismic node, wherein the time drift measurement is performed in the at least one seismic node. The seismic node is configured for receiving a master clock signal and obtaining a time drift between the slave clock and the master clock signal.

A wireless seismic data acquisition unit with a wireless receiver providing access to a common remote time reference shared by wireless seismic data acquisition units in a seismic system. The receiver can replicate local version of remote time epoch to which a seismic sensor analog-to-digital converter is synchronized. The receiver can replicate local version of remote common time reference to time stamp local node events. The receiver can be placed in a low power, non-operational state over periods of time during which the unit continues to record seismic data, thus conserving unit battery power. The system corrects the local time clock based on intermittent access to the common remote time reference. The system corrects the local time clock via a voltage controlled oscillator to account for environmentally induced timing errors. The system provides a more stable method of correcting drift in the local time clock.

In some embodiments, an apparatus and a system, as well as a method and an article, may operate to receive a derived clock signal downhole, the derived clock signal being derived from a surface clock signal (associated with a surface clock), such that the frequency of the derived clock signal is less than the frequency of the surface clock signal. Further activity may include measuring the frequency of the derived clock signal in terms of an uncorrected downhole clock frequency (associated with a downhole clock) to provide a measured frequency equivalent, and correcting time measurements made using the downhole clock, based on the measured frequency equivalent, or based on an actual frequency of the downhole clock determined according to the measured frequency equivalent. Additional apparatus, systems, and methods are described.

Disclosed is a method for determining skew measurements for clock errors in an autonomous seismic node. A parabolic fit may be used to estimate the clock drift of an ocean bottom seismic node during node deployment. A temperature and/or frequency trend and a real-time temperature measurement may be used to compute a temperature corrected parabolic trend. The temperature and/or frequency trend may be measured in a laboratory on a node by node basis or it may be a single trend that is suitable for all nodes. The method may include measuring clock skew prior to node deployment and after node recovery, correcting the pre and post deployment skew measurements based on a temperature and/or frequency trend and/or to a constant reference temperature, and/or computing a parabolic trend of the skew measurements of the clock based on the temperature corrected pre and post deployment skew measurements.

A System including multiple data acquisition units. A data acquisition unit includes a housing whose interior volume is defined by an outer wall, a top part and a bottom part; the housing includes a geolocation unit for processing a time synchronisation signal, a data communication unit for enabling wireless data communication with an external gateway device, a processing unit, a geophone assembly in the housing to sense vibration received via a sensing probe, extending from the bottom part of the housing, and/or the housing and to generate output signals to the processing unit, and a power supply unit to supply power to the geolocation unit, the data communication unit and the processing unit; a geolocation antenna and a data communication antenna extending from the top part of the housing; the processing unit processes the output signals from the geophone assembly to determine an occurrence of a seismic event.

A method and apparatus may include activating, by a network node, power of a global-positioning-system receiver or power of an active antenna of the global-positioning-system receiver. The apparatus uses the global-positioning-system receiver to perform synchronization of the apparatus. The method may include receiving at least one measurement, wherein the at least one measurement includes real-time, predictive, or historic data. The method may also include determining a holdover duration based on the at least one measurement. The holdover duration corresponds to a length of time where the power of the global-positioning-system receiver or the power of the active antenna is to be turned off. The method may also include deactivating the power of the global-positioning-system receiver or the power of the active antenna for the holdover duration.

Respective embodiments disclosed herein include methods and apparatuses (1) for surveying a mine bench or other material body using at least seismic data obtained via geophone and measurement module data synchronized via a wireless link; (2) for generating hyperspectral panoramic imaging data of a blast hole or other borehole; or (3) for allowing a neural network to facilitate a differential blast design that targets a first bench part more weakly than the differential blast design targets a second bench part (along the same mine bench) at least partly based on data indicative of a much higher concentration of a valuable material in the second bench part than in the first.