WO2015176080A9

WO2015176080A9 - Borehole location identification

Info

Publication number: WO2015176080A9
Application number: PCT/ZA2015/000034
Authority: WO
Inventors: Craig Charles Schlenter
Original assignee: Detnet South Africa (Pty) Limited
Priority date: 2014-05-15
Filing date: 2015-05-12
Publication date: 2016-07-14
Also published as: AU2015101869A4; AU2015258825A1; WO2015176080A2; ZA201602946B; AU2015101869A6; WO2015176080A3

Abstract

in a blasting system positional data for a borehole or detonator generated by the use of a remote reference source is corrected by applying thereto a correction factor, determined by comparing absolute positional information of a reference location to positional information of the reference location generated by the use of the remote reference source.

Description

BOREHOLE LOCATION IDENTIFICATION

BACKGROUND OF THE INVENTION

[0001] This invention relates generally to a blasting system and more particularly to the accurate identification of the geographical position of boreholes in a blasting system. [0002] A GNSS (global navigation satellite system) can be used to establish the geographical position of each borehole in a plurality of boreholes in a blasting system, with a fair degree of accuracy. Nonetheless, the accuracy of GNSS data is subject to extraneous factors such as meteorological conditions, ephemeris and clock errors, and the like. Typically the accuracy of GNSS positional data may be subject to a variation or tolerance of several meters. [0003] Electronic detonators can execute timing intervals, used to determine or control a blasting pattern, with an accuracy of the order of milliseconds or better. The benefit of this degree of timing accuracy is however negated, to some extent, by the relatively inaccurate positional data if such data is used to establish blast timing i.e. the time instant at which a detonator is ignited. [0004] Various techniques have been proposed to address positional data errors which are attributable to operating factors associated through the use of a GNSS. In US 7156023 a feed transmitter supplies correction data over a transmission link to a device which provides data on the position of each borehole in a blasting system. The correction data presumably could be provided using the RTCM standard. The provision of this type of transmission link can however be cumbersome. [0005] An object of the present invention, in one respect, is to eliminate the need for a real time transmission link to supply correction data of the kind referred to.

SUMMARY OF THE INVENTION

[0006] The invention provides a method of establishing positional data for each borehole in a plurality of boreholes in a blasting system, wherein each borehole is respectively associated with at least one detonator, the method including the steps of:

1 . establishing a base station with known geographical positional information,

2. at the base station over a given time interval recording, as a function of time, GNSS information which is derived at least from a GNSS receiver,

3. over said given time interval, or a subset thereof, utilising a data logger to log, as a function of time, GNSS information for each of a plurality of boreholes in the blasting system, and a unique identity for each borehole or for each detonator, and

4. using the geographical positional information, referred to in step (1 ), the GNSS information recorded in step (2) and the GNSS information logged in step (3) to derive corrected positional information for each borehole or detonator.

The term "GNSS information" as used herein may include any information derivable from a GNSS system, as indicated in step (2) and additionally or alternatively, derived from a related data source or system component including but not limited to any combination of the following sources of information:

· information relating to a clock or an oscillator in an earth-based device;

• information relating to a clock of a satellite-based device;

• information relating to the phase of a transmission signal from a satellite-based device; • GNSS ephemeris information;

• information about errors in data transmitted from a satellite-based device derived from a SBAS (satellite based augmentation system) or other sources including internet accessible GNSS correction data;

· positional information; and

• any data available in the following GNSS related standards;

o RINEX - receiver independent exchange format;

o RTCM - Radio Technical Commission for Maritime Services;

o SBAS - satellite based augmentation system; and

o WAAS - wide area augmentation system.

[0007] A benefit of the invention lies in the fact that the base station need not be in direct communication, real time or otherwise, with the data logger. However, the GNSS information recorded at the base station is recorded over at least the time interval during which the data logger is used to record GNSS information relating to borehole or detonator positions. In step (4) the data from steps (1 ), (2) and (3), are used to derive the borehole or detonator positional information using time as a common reference.

[0008] Algorithms used to correct the data are described inter alia in the manual for the RTKLIB software library from www.rtklib.com. While the details may be complex, in simple terms the known location of the base station enables the determination of errors associated with the range data received from each satellite. This in turn allows correction data to be derived to compensate for these errors. The correction data may in turn be used to adjust the range data recorded on the data logger thus allowing the calculation of a more accurate position than would be available without the correction data. Additional data from other sources such as atmospheric models, internet based correction data or SBAS and the like, may be used to correct for atmospheric related errors, and satellite position errors, to remove faulty satellite data, and the like. [0009] The invention further extends to a method of generating positional data for a borehole or of a detonator in a blasting system wherein positional data for the borehole or for the detonator, generated by the use of a remote reference source is corrected by applying thereto a correction factor, determined by comparing absolute positional information of a reference location to positional information of the reference location generated by the use of the remote reference source.

BRIEF DESCRIPTION OF THE DRAWING

[0010] The invention is further described by way of example with reference to the accompanying drawing which is a schematic representation of one manner in which the method of the invention can be implemented. DESCRIPTION OF PREFERRED EMBODIMENT

[0011] The accompanying drawing illustrates part of a blasting system 10 which includes a plurality of boreholes 12A, 12B, 12C ... 12N formed in a body of rock 14. At least one detonator 16A, 16B ... 16N is placed in each respective borehole. This is exemplary only and non-limiting for, depending on requirement, two or more detonators can be placed in a single borehole. Each borehole is filled, as is known in the art, with explosive material 18. [0012] In this example the detonators 16 are interconnected by means of respective branch lines 20A, 20B ... 20N to a main harness 24. In use a blasting machine 26 is connected to the harness 24. A plurality of blasting machines and harnesses may be used if required.

[0013] A base station 30 is established near the blasting system 10 at a suitable site. The geographical position of the base station is accurately given by means of positional data 32 determined and validated in a plurality of ways known in the art. A plurality of base stations may be used if desired.

[0014] The base station includes a data recorder 34.

[0015] A processor 40 is used in the implementation of the method of the invention. The processor may be mobile, associated with the base station, associated with the blasting machine, associated with the data recorder 34 or be installed at a control location. The invention is not limited in this respect. In one embodiment the processor 40 is provided in conjunction with a hand-held data logger 42 which is used by an operator 44.

[0016] The recorder 34 has the capability of logging GNSS information received from at least one GNSS data source 46 or derived from local information such as an internal clock associated with a GNSS receiver, on a time basis. The recorder 34 may also log information from other data sources such as internet-based GNSS data correction sources.

[0017] In practice the operator 44 goes to each of the boreholes 12A, 12B in any suitable sequence. Each borehole or detonator has a unique identity 50A, 50B ... 50N associated with it. The operator is required to position the logger 42 as close as is possible to each borehole or detonator, in turn. When the logger is at a borehole 12K the respective identity data 50K is logged and, substantially simultaneously, GNSS data from the data source 46 is logged to record the geographical position of the borehole 12K as determined by the data source. This is done on a time basis.

[0018] Additional GNSS data may be logged, if desired, as the operator 44 moves between the boreholes 12 in order to track the movement of the operator between the boreholes. The identity data 50K may be associated with a particular detonator and not with a borehole in which the detonator is positioned. It is possible for the identity data to be assigned automatically, sequentially or otherwise, to the detonators by the data logger if required. For boreholes with multiple detonators, the data logger may also record information about the depth of the detonator in the borehole derived through suitable means such as user input or stored internally in the detonator at the time of manufacture, based for example on the detonator harness length or the length of a branch line to the detonator. The detonators may of course simply be numbered sequentially in a borehole according to a given convention e.g. detonator 1 may be at the bottom of a borehole, detonator 2 may be the first higher up detonator from detonator 1 , and so on.

[0019] The operator logs the borehole or detonator position, in the aforementioned manner, during a known time interval and, during that same time interval the recorder 34 operates automatically without requiring real-time communication with the data logger 42.

[0020] Once the positions of all of the boreholes or detonators have been logged by the operator, at any appropriate time thereafter, the data from the recorder 34 is retrieved.

[0021] In the processor 40 a programme is executed to analyse the recorded data 34 and to apply the data 32 which is accepted as correctly identifying the position of the base station, to determine those errors in the data held in the recorder 34 which are attributable to variations in the accuracy of the data obtainable from the data source 46. A table 60 of corrections, applicable to the data in the recorder 34, on a time basis, is generated by the programme.

[0022] Data 62 from the data logger 42 is also held on a time scale but linked, in respect of each borehole or detonator, to the unique identity of that borehole or the identities of the detonators associated with the respective borehole. Correction factors available from the table 60 are applied to the data 62 by a correlator 64, using time as a common factor. The correlation process produces a table 66 of corrected borehole data which consists of corrected geographical or positional data of each borehole linked to the unique identifier of that borehole or the identity of each of the detonators associated with the respective borehole.

[0023] In carrying out the aforementioned process it is assumed that variations which could affect the accuracy of the data logged by the logger 42, affect, substantially to the same extent, the accuracy of the data 32 retained in the recorder 34. As the true geographical position of the base station 30 is known the error in the data 32 in the recorder 34 can be determined. It is taken that the same degree of error manifests itself in the data 62 in the data logger 42.

[0024] The corrected positional data 66 is available for subsequent use (step 70) e.g. in determining time delays in the individual detonators. These delays can be programmed into the detonators 12 using the blasting machine 26 or any other appropriate mechanism. The corrected borehole data 66 may be displayed on a geographical map or on or in other suitable graphical representation, using an appropriate tool to aid with blast design for the blasting system 10. [0025] Additional corrections may be applied to the data 32, the borehole data 62, the corrected data 60 or the corrected borehole data 66, based on data derived from various sources e.g. atmospheric modelling, SBAS, WAAS and the like. Data deemed incorrect may be removed from processing e.g. a satellite may transmit an incorrect position and this may be ignored as is known in the art.

Claims

A method of establishing positional data for each borehole in a plurality of boreholes in a blasting system, wherein each borehole is respectively associated with at least one detonator, the method including the steps of: (1 ) establishing a base station with known geographical positional information,

(2) at the base station over a given time interval recording, as a function of time, GNSS information which is derived at least from a GNSS receiver,

(3) over said given time interval, or a subset thereof, utilising a data logger to log, as a function of time, GNSS information for each of a plurality of boreholes in the blasting system, and a unique identity for each borehole or for each detonator, and

(4) using the geographical positional information, referred to in step (1), the GNSS information recorded in step (2) and the GNSS information logged in step (3) to derive corrected positional information for each borehole or detonator.

A method according to claim 1 wherein the GNSS information includes information derived from at least one of the following sources of information:

information relating to a clock or an oscillator in an earth-based device;

information relating to a clock of a satellite-based device;

information relating to the phase of a transmission signal from a satellite-based device;

GNSS ephemeris information; information about errors in data transmitted from a satellite-based device derived from a SBAS (satellite based augmentation system) or other sources including internet accessible GNSS correction data;

positional information; and

any data available in the following GNSS related standards;

o RINEX - receiver independent exchange format;

o RTCM - Radio Technical Commission for Maritime Services;

o SBAS - satellite based augmentation system; and

o WAAS - wide area augmentation system.

A method according to claim 1 or 2 which includes the step of using the data logger to allocate said unique identity for each borehole or for each detonator.

A method according to claim 1 , 2 or 3 wherein the corrected positional data for each borehole or detonator is determined, at least in part, by establishing an error in the GNSS positional information for the base station, and using that error to correct the GNSS information, logged by the data logger, for such borehole or detonator.

A method of generating positional data for a borehole or of a detonator in a blasting system wherein positional data for the borehole or for the detonator, generated by the use of a remote reference source is corrected by applying thereto a correction factor, determined by comparing absolute positional information of a reference location to positional information of the reference location generated by the use of the remote reference source.