Method and apparatus for correcting timing function in nodal seismic data acquisition unit

Abstract

The invention relates to a method and an apparatus for correcting a timing function in a nodal seismic data acquisition unit. A wireless seismic data acquisition unit comprises a wireless receiver providing access to a common remote time reference shared by a plurality of wireless seismic data acquisition units in a seismic system. The receiver is capable of replicating a local version of a remote time epoch to which a seismic sensor analog-to-digital converter is synchronized. The receiver is capable of replicating a local version of remote common time reference for the purpose of time stamping local node events. The receiver is capable of being placed in a low power, non-operational state over periods of time during which the seismic data acquisition unit continues to record seismic data, and therefore unit battery power is conserved. The system implements a method to correct the local time clock based on intermittent access to the common remote time reference. The method corrects the local time clock via a voltage controlled oscillator to solve environmentally induced timing errors. The invention further provides a method of correcting drift in the local time clock.

Description

[0001] This application is a divisional application of the application number 200880112633.4, the application date is November 4, 2008, and the invention title is "Method and device for correcting timing function in node seismic data acquisition unit". [0002] Cross References to Related Applications [0003] This application claims U.S. Provisional Patent Application No. 60 / 994,711 filed September 21, 2007 (21.09.2007) and U.S. Non-Provisional Patent Application No. 11 / 977,580, which are entitled "Method and Apparatus for Correcting the timing function in a Nodal Seismic Data Acquisition Unit," which are hereby incorporated by reference. technical field [0004] The present invention relates to the field of seismic exploration. More particularly, the present invention relates to methods and apparatus for the control and correction of time bases used in distributed nodal seismic acquisition systems. Background technique [0005] Seismic exploration generally utilizes a s...

AI Technical Summary

Problems solved by technology

However, as the number of seismic sensors connected to an acquisition unit approaches one, the percentage of the unit's total power budget used to maintain wireless synchronization becomes more important, and power becomes the limiting factor in managing the deployment length of a seismic acquisition unit

[0017] Second, wireless access to an external time reference 20 will be significantly more difficult for nodal acquisition seismic units compared to centralized base unit receivers (e.g. recording trucks)

Although these GPS-trained time bases typically allow some limited control over the incidence of the control loop, resulting in some reduction in distortion caused by changes in the VCO operating frequency, this reduction in incidence is greatly dramatically increases the time intervals during which corrections are made and the GPS receiver must remain in a state of high power consumption

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