Positioning correction system and method for single and multi-channel ground penetrating radar

• US 20090109081A1
• Filed: 10/30/2008
• Published: 04/30/2009
• Est. Priority Date: 10/30/2007
• Status: Active Grant

• Current Assignee: Underground Imaging Technologies, Inc. (Caterpillar Incorporated)
• Original Assignee: Underground Imaging Technologies, Inc. (Caterpillar Incorporated)
• Inventors: Sjostrom, Keith J., Ryerson, Kenneth J., Hanson, David
• Granted Patent: US 7,612,704 B2
• Time in Patent Office: Days
• US Class Current: 342/22
• CPC Class Codes: G01S 13/885 for ground probing prospecting or detecting using electromagnetic waves G01V3/12
• CPC Class Codes: G01V 3/12 operating with electromagnetic waves operating with millimetre waves G01V8/005

Abstract

A mobile geophysical instrument produces geophysical data sets each associated with a position computed by use of a position sensor. A variable time delay results between a time when data for each geophysical data set is collected and a time when a position associated with each geophysical data set is recorded. A module receives distance transducer data and includes circuitry configured to generate a module signal based on trigger signals from the distance transducer and a calibration value. A data acquisition system (DAS) receives geophysical data sets from the geophysical instrument, positioning data from the positioning sensor, and the module signals. The DAS generates a DAS timestamp in response to each module signal and associates the DAS timestamp with each geophysical data set and a position associated with the geophysical data set, so as to substantially eliminate the variable time delay.

Claims

1. A system, comprising:

a mobile ground penetrating radar (GPR) system, comprising;

an apparatus configured for movement over terrain;

a GPR sensor mounted to the apparatus and configured to produce GPR scan data;

a positioning sensor supported by the apparatus;

a wheel encoder supported by the apparatus and configured to generate trigger signals for initiating GRP sensor scans; and

a processor coupled to memory and supported by the apparatus, the processor coupled to the GPR sensor, the positioning sensor, and the wheel encoder, the processor configured to execute program instructions stored in the memory for collecting data for each GPR scan and recording position data for each GPR scan;

wherein a variable time delay results between a time when the GPR scan data is collected and a time when the position data associated with the GPR scan data is recorded;

an encoder capture module (ECM) adapted for attachment to the apparatus, the ECM comprising;

an input adapted to receive the trigger signals generated by the wheel encoder;

circuitry coupled to the input and configured to generate an ECM signal based on each trigger signal and a calibration value; and

an output; and

a data acquisition system coupled to the output of the ECM and configured to receive GPR scan data from the GPR sensor, positioning data from the positioning sensor, and the ECM signals from the ECM, the data acquisition system configured to generate a DAS timestamp in response to each ECM signal and to associate the DAS timestamp with the GPR scan and the GPS position associated with the GRP scan, so as to substantially eliminate the variable time delay.

2. The system of claim 1, wherein a distance between GPR scans as computed from the GPS position data is not the same as that which can be computed using the wheel encoder due to the variable time delay.

3. The system of claim 1, wherein the variable time delay is unpredictable with respect to when the variable time delay occurs.

4. The system of claim 1, wherein the variable time delay is uncorrectable by way of introduction of a constant time offset applied between the time when data for each GPR scan is collected by the processor and the time when the position associated with each GPR scan is recorded by the processor.

5. The system of claim 1, wherein the ECM comprises a controller and a counter.

6. The system of claim 5, wherein the counter comprises a quadrature cycle counter.

7. The system of claim 1, wherein the calibration value is indicative of a predetermined relationship between a number of wheel encoder ticks and a known distance.

8. The system of claim 1, wherein communication between the ECM and the DAS is bidirectional, and the calibration value is transmitted by the DAS to the ECM.

9. The system of claim 1, wherein the DAS is configured to generate a position marker file comprising data of each GPR scan and a timestamp associated with the data of each GPR scan.

10. A system, comprising:

a mobile geophysical instrument configured for traversing along an above-ground path, a processor, a distance transducer configured to produce trigger signals, and a position sensor, the geophysical instrument configured to produce a plurality of geophysical data sets as the geophysical instrument traverses the above-ground path, wherein data for each geophysical data set is associated with a position computed by use of the position sensor, a variable time delay resulting between a time when data for each geophysical data set is collected by the processor and a time when a position associated with each geophysical data set is recorded by the processor;

a module adapted for attachment to the geophysical instrument, the module comprising;

an input adapted to receive the distance transducer data;

circuitry coupled to the input and configured to generate a module signal based on each trigger signal and a calibration value; and

an output; and

a data acquisition system (DAS) coupled to the output of the module and configured to receive geophysical data sets from the geophysical instrument, positioning data from the positioning sensor, and the module signals, the data acquisition system configured to generate a DAS timestamp in response to each module signal and to associate the DAS timestamp with each geophysical data set and a position associated with the geophysical data set, so as to substantially eliminate the variable time delay.

11. The system of claim 10, the geophysical instrument comprises a ground penetrating radar.

12. The system of claim 10, the distance transducer comprises a wheel encoder.

13. The system of claim 10, wherein the module comprises a controller and a quadrature cycle counter.

14. The system of claim 10, wherein the calibration value is indicative of a predetermined relationship between a number of distance transducer output intervals and a known distance.

15. The system of claim 10, wherein communication between the module and the DAS is bidirectional, and the calibration value is transmitted by the DAS to the module.

16. The system of claim 10, wherein the DAS is configured to generate a position marker file comprising data of each geophysical data set and its associated timestamp.

17. A module adapted for use with a system comprising a data acquisition system (DAS) and a mobile ground penetrating radar (GPR) system, the GPR system comprising a GPR sensor, a processor, a distance transducer configured to produce trigger signals, and a position sensor, the GPR system configured to produce scans of GPR data, wherein data for each GPR scan is associated with a position computed by use of the position sensor, a variable time delay resulting between a time each scan of GPR data is collected by the processor and a time a position associated with each scan of GPR data is recorded by the processor, and the DAS configured to receive GPR scan data from the GPR sensor, positioning data from the positioning sensor, and signals from the module, the DAS configured to generate a DAS timestamp based on each module signal and to associate the DAS timestamp with each GPR scan and a position associated with the GRP scan, the module comprising:

an input adapted to receive the trigger signals;

circuitry coupled to the input and configured to generate a module signal based on each trigger signal and a calibration value; and

an output that provides the module signal for use by the DAS to generate a DAS timestamp that can be associated with each GPR scan and a position associated with the GRP scan so as to substantially eliminate the variable time delay.

18. The module of claim 17, comprising a controller and a counter.

19. The module of claim 17, comprising a controller and a quadrature cycle counter.

20. A system, comprising:

a wheel encoder;

a time-based sensor;

a distance-based sensor coupled to the wheel encoder, wherein sensor readings from the distance-based sensor are made in response to trigger signals produced by the encoder wheel;

an encoder module configured to receive the trigger signals and generate encoder module signals using the trigger signals and a calibration value;

a computer clock time generator responsive to the encoder module signals and configured to assign a computer clock time to the sensor readings from the distance-based sensor and to sensor readings from the time-based sensor; and

a processor configured to merge the distance-based sensor readings with the time-based sensor readings based on synchrony between the respective computer clock times of the distance-based sensor readings with the time-based sensor readings, the processor configured to generate an output file comprising at least the distance-based sensor readings and their respective computer clock times.

21. The system of claim 20, wherein the processor is configured to produce a geospatial position for each encoder module signal.

22. The system of claim 20, wherein the distance-based sensor comprises a geophysical instrument and the time-based sensor comprises a position sensor.

23. The system of claim 20, wherein the distance-based sensor comprises a ground penetrating radar and the time-based sensor comprises a GPS sensor.

24. A method, comprising:

collecting a plurality of geophysical data sets in response to trigger signals produced by a distance transducer while a geophysical instrument traverses an above-ground path;

computing a position of the geophysical instrument while the geophysical instrument traverses the above-ground path;

associating, in response to the trigger signals, the geophysical data sets with computed positions, a variable time delay resulting between a time when data for each geophysical data set is collected and a time when the position associated with each geophysical data set is recorded;

producing an adjusted trigger signal based on each trigger signal and a calibration value;

generating a timestamp that can be associated with each geophysical data set and a position associated with the geophysical data set so as to substantially eliminate the variable time delay.