Local Clock Frequency Gauging for Seismic Data Acquisition

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Solution Overview

Problem

Wireless seismic data acquisition networks face challenges in maintaining accurate temporal synchronization and minimizing energy consumption due to the need for expensive and energy-intensive oscillator synchronization with satellite-based positioning systems.

Innovation Solution

A method and apparatus that utilize a low-cost oscillator with a TCXO, where the sampling frequency is gauged by a satellite-based positioning system, allowing for accurate time-stamping and resampling of data to correct frequency errors, enabling accurate data acquisition while reducing the need for continuous satellite system usage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If an oscillator is permanently slaved to the satellite-based positioning system to ensure accurate sampling frequency, then temporal synchronization accuracy is improved, but energy consumption increases and autonomy is reduced

Engineering Contradiction:

Improvetemporal synchronization accuracyVSAvoidenergy consumption

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The patent applies preliminary action by performing frequency gauging of the local oscillator against the satellite-based positioning system at specific moments (when GPS is available) before actual data acquisition. The gauging results (frequency error measurements) are stored and used to correct sampling timestamps during offline processing, eliminating the need for continuous GPS operation while maintaining temporal accuracy.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent creates a copy of the reference time frequency information by measuring and storing the frequency error between the local oscillator and GPS time during gauging periods. This copied frequency error data is then applied to correct sampling timestamps during offline processing, replacing the need for continuous real-time GPS synchronization and reducing energy consumption.

Inventive Principle:

Principle #26Copying

2Use of energy by moving object

If a high-stability oscillator is used to maintain accurate sampling frequency without continuous GPS synchronization, then energy consumption is reduced, but temporal synchronization accuracy deteriorates

Engineering Contradiction:

Improveenergy consumptionVSAvoidtemporal synchronization accuracy

Core Design Contradiction:

Use of energy by moving objectVSMeasurement precision

Solution Approach 1:

The patent replaces the mechanical/physical continuous synchronization system (permanent GPS connection and closed-loop PLL/VCXO) with a computational approach. Frequency gauging is performed intermittently when GPS is available, and the measured frequency error is used in offline timestamp correction algorithms, substituting continuous physical synchronization with periodic measurement and computational correction.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent performs preliminary frequency gauging and error measurement when GPS signals are available, storing these calibration data for later use. This preliminary action allows the system to operate independently of continuous GPS while maintaining accuracy through pre-acquired reference information.

Inventive Principle:

Principle #10Preliminary action

3Duration of action of stationary object

If the satellite-based positioning system is turned off to reduce energy consumption, then autonomy is improved, but the ability to maintain accurate sampling frequency is worsened

Engineering Contradiction:

Improveautonomy durationVSAvoidsampling frequency accuracy

Core Design Contradiction:

Duration of action of stationary objectVSMeasurement precision

Solution Approach 1:

The patent performs frequency gauging and error measurement in advance when GPS is available, storing these calibration parameters for later offline processing. This preliminary calibration enables the system to operate autonomously for extended periods without GPS while maintaining sampling frequency accuracy through computational correction of timestamps using the pre-acquired frequency error data.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS7548600B2Apparatus and method for compensating the drift of a local clock used as sampling frequency

Publication Date: 2009.06.16 SERCEL SAS

AI summary

The invention relates to an apparatus and a method for data acquisition, the apparatus being characterized in that it comprises an analog/digital converter (510) sampling at an imperfect frequency FE provided by a local clock (100) data acquired by a sensor (500) thus providing a series of sampled and dated data E[k], a time-stamping module (300) for measuring the frequency error of the local clock (100) by determining the sampling dates according to a universal time UTC(t), and a resampling module (400) for correcting the sampled and dated data E[k].