WO2008117081A2 - Terrain correction systems - Google Patents
Terrain correction systems Download PDFInfo
- Publication number
- WO2008117081A2 WO2008117081A2 PCT/GB2008/050113 GB2008050113W WO2008117081A2 WO 2008117081 A2 WO2008117081 A2 WO 2008117081A2 GB 2008050113 W GB2008050113 W GB 2008050113W WO 2008117081 A2 WO2008117081 A2 WO 2008117081A2
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- WO
- WIPO (PCT)
- Prior art keywords
- data
- potential field
- time
- terrain
- field
- Prior art date
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- 238000012937 correction Methods 0.000 title claims abstract description 43
- 238000005259 measurement Methods 0.000 claims abstract description 55
- 238000000034 method Methods 0.000 claims abstract description 41
- 230000005484 gravity Effects 0.000 claims abstract description 21
- 238000012545 processing Methods 0.000 claims abstract description 20
- 238000013507 mapping Methods 0.000 claims abstract description 16
- 230000006870 function Effects 0.000 claims description 10
- 230000004044 response Effects 0.000 claims description 9
- 238000004364 calculation method Methods 0.000 claims description 6
- 238000001914 filtration Methods 0.000 claims description 6
- 230000000694 effects Effects 0.000 abstract description 3
- 238000004590 computer program Methods 0.000 abstract description 2
- 230000001133 acceleration Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000003384 imaging method Methods 0.000 description 2
- 230000003278 mimic effect Effects 0.000 description 2
- 238000012876 topography Methods 0.000 description 2
- 230000004075 alteration Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 230000004907 flux Effects 0.000 description 1
- 238000005755 formation reaction Methods 0.000 description 1
- 229910052500 inorganic mineral Inorganic materials 0.000 description 1
- 230000010354 integration Effects 0.000 description 1
- 238000007620 mathematical function Methods 0.000 description 1
- 239000011707 mineral Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 230000000149 penetrating effect Effects 0.000 description 1
- 239000011435 rock Substances 0.000 description 1
- 238000005070 sampling Methods 0.000 description 1
- 238000012732 spatial analysis Methods 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
- G01V7/00—Measuring gravitational fields or waves; Gravimetric prospecting or detecting
- G01V7/16—Measuring gravitational fields or waves; Gravimetric prospecting or detecting specially adapted for use on moving platforms, e.g. ship, aircraft
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F17/00—Digital computing or data processing equipment or methods, specially adapted for specific functions
- G06F17/10—Complex mathematical operations
- G06F17/14—Fourier, Walsh or analogous domain transformations, e.g. Laplace, Hilbert, Karhunen-Loeve, transforms
Definitions
- This invention relates to methods, apparatus and computer program code for processing data from potential field surveys to correct for the effects of underlying terrain.
- Embodiments of the techniques are particularly useful for processing data from airborne surveys, in particular gravity field surveys.
- a potential field survey is performed by measuring potential field data which, for a gravity survey, may comprise one or more of gravimeter data (measuring gravity field) or gravity gradiometer data (measuring gravity field gradient), vector magnetometer data, true magnetic gradiometer data, and other types of data well-known to those skilled in the art.
- a common aim of a geophysical potential field survey is to search for signatures which potentially indicate valuable mineral deposits.
- airborne potential field surveys such as gravity surveys are flown on a grid pattern.
- the grid is defined by orthogonal sets of parallel lines (flight paths) on a two-dimensional surface which is draped over the underlying terrain.
- the draped surface is constrained by the closest the aircraft is permitted to fly to the ground and the maximum rate of climb/descent of the aircraft.
- a terrain correction is generally applied, compensating for surface height variations.
- Surface data may be purchased in the form of digital terrain elevation data or determined from (D)GPS ((Differential) Global Position System) and/or airborne techniques such as LIDAR (Laser Imaging Detection and Ranging) and SAR (synthetic aperture radar). Aircraft acceleration, attitude, angular rate and angular acceleration data may also be used to correct the output data of the potential field instrumentation.
- D digital terrain elevation data
- LIDAR Laser Imaging Detection and Ranging
- SAR synthetic aperture radar
- One problem arises where the terrain changes rapidly so that spatial aliasing can arise, more particularly where the terrain has peaks or other variations on a length scale which is less than the distance between the survey (flight) lines.
- a method of processing potential field measurement data from a moving platform potential field survey for mapping a field comprising: inputting said measured potential field data, said measured potential field data comprising data defining a time series of potential field measurements captured by a potential field measurement instrument mounted on a moving platform, each of said measurements having associated data defining positions of said measurements as a function of time; inputting terrain data defining a spatial variation of terrain surveyed by said potential field survey; determining time-domain correction data to be applied to said measured potential field data in the time-domain, said determining using said terrain data and said associated data defining positions of said measurements as a function of time; and adjusting said measured potential field data defining said time series of potential field measurements using said time-domain correction data to provide terrain corrected measured potential field data for said mapping of said field.
- the method is implemented off-line, after collection of the potential field data using the moving platform.
- the correction is however performed in the time- domain by means of a forward calculation from data in a terrain model database to the time series of measurement locations.
- the determining of the time-domain correction data includes compensating for a bandwidth of the potential field measuring instrument.
- this comprises filtering the time-domain correction data using a filter matched to the response, for example an impulse response, of the instrument.
- This may comprise, for example, integrating measurements over an integration time interval dependent upon a response of the potential field measurement instrument.
- the time-domain correction data comprises a set of calculated values of the measured potential field due to the terrain at three-dimensional positions in space along survey lines of the potential field survey. However in general these positions will not correspond to the actual recorded measurement positions. Instead preferably positions of the moving platform at regularly spaced intervals in time (and thus depend upon the speed of the moving platform).
- the time-domain correction data comprises an effective component of the field measurement instrument data forward calculated from the terrain data at three- dimensional positions in space x(t), y(t), z(t) at substantially regularly spaced time intervals.
- This contribution to the potential field due to the terrain as a function of position in space of the moving platform at regular time intervals may then be subtracted from the actual potential field measurements to leave a signal of interest for further data processing, in particular due to underlying geological formations.
- Either or both of the actual, measured signal and terrain correction signal may optionally be extrapolated and/or interpolated so that corresponding data points substantially align for performing the correction.
- the method further comprises determining a set of field mapping parameters mapping the field using the adjusted measured potential field data.
- the moving platform comprises an aircraft and the survey comprises an airborne potential field survey, but the techniques we describe may also be applied to marine or land-based potential field surveys from a water or land craft.
- the invention further provides processor control code to implement the above-described methods, in particular on a data carrier such as a disk, CD- or DVD-ROM, programmed memory such as read-only memory (Firmware), or on a data carrier such as an optical or electrical signal carrier.
- Code (and/or data) to implement embodiments of the invention may comprise source, object or executable code in a conventional programming language (interpreted or compiled) such as C, or assembly code, code for setting up or controlling an ASIC (Application Specific Integrated Circuit) or FPGA (Field Programmable Gate Array), or code for a hardware description language such as Verilog (Trade Mark) or VHDL (Very high speed integrated circuit Hardware Description Language).
- code and/or data may be distributed between a plurality of coupled components in communication with, one another, for example distributed across a network.
- the invention further provides a data processing system configured to implement embodiments of the above-described methods.
- a data processing system for processing potential field measurement data from a moving platform potential field survey for mapping a field
- the system comprising: data memory for storing measured potential field data, said measured potential field data comprising data defining a time series of potential field measurements captured by a potential field measurement instrument mounted on a moving platform, each of said measurements having associated data defining positions of said measurements as a function of time, and for storing terrain data defining a spatial variation of terrain surveyed by said potential field survey; and program memory storing processor control code; and a processor coupled to said data memory and to said program memory to load and implement said control code, said code comprising code to: input said measured potential field data and said associated data for said measurements; input said terrain data; determine time-domain correction data to be applied to said measured potential field data in the time-domain using said terrain data and said associated data defining positions of said measurements as a function of time; and adjust said measured potential field data defining said time series of potential field measurements using said time- domain correction data to provide terrain corrected measured potential
- the code also comprises code to adjust the correction data by means of a matching filter to mimic a response of the measurement instrument.
- Figure 1 shows, schematically, a graph of height against distance illustrating a section of terrain under a flight line of an airborne potential field survey.
- Figure 2a shows, schematically, variation of gravity gradient component G zz with time based on a forward calculation from the terrain model of Figure 1 at regularly spaced time intervals and Figure 2b shows the adjusted forward calculated data after filtering in the time domain using a filter to match the response of the measurement system;
- Figure 3 illustrates the difference between the time domain terrain correction data before and after the filtering stage
- Figure 4 shows, schematically, a flow diagram of a procedure for implementing an embodiment of a method according to the invention.
- a field in particular a gravity field
- this is not limited to a vector field but includes scalar and tensor fields, a potential field and any derivatives deriving from the potential field.
- Potential field data includes, but is not limited to, gravimeter data, gravity gradiometer data, vector magnetometer data and true magnetic gradiometer data. Elements and representations of a potential field may be derived from a scalar quantity.
- this shows an example survey flight line above terrain, in which the arrow shows the direction of flight.
- Figure 2b shows forward calculated Gzz in the time domain and Figure 2b shows the forward calculated Gzz after filtering to instrument bandwidth.
- Figure 3 shows the difference between the curves of Figures 2a and 2b, showing the alteration of the terrain correction due to the filtering. Time-domain correction techniques
- the terrain correction By performing a terrain correction early on in the processing sequence, when the data is still represented in the time domain, one can ultimately produce a better map of the underlying geology because the terrain correction can be matched more closely to the data that was actually recorded by the instrument. In particular, the time domain correction will correctly remove high frequency terrain signals which would otherwise be aliased in spatial analysis. Also, by performing the correction in the same domain as the measurement system, the actual transfer function of the measurement instrument can be incorporated into the correction data. This means that the terrain correction is removing the effect the terrain has on the recorded measurement data rather than removing the terrain signal itself. This is important especially for airborne surveys flown at low altitude over highly variable terrain since the bandwidth of the measurement system can significantly alter the high frequency terrain signals.
- Figure 4 shows a flow diagram of steps involved in a preferred dynamic terrain correction; this procedure may be implemented in software on a carrier such as a disk, or in a computer system, as schematically illustrated.
- the geometry of a 3D model of the terrain is constructed using available topography and bathymetry data.
- the assignment of density values within the model is guided by information originating from rocks types, well data or surface penetrating imaging techniques.
- the resolution of the model should be adequate to accurately recreate the surveyed potential field data from the terrain.
- the model has an extent which goes beyond the boundaries of the survey by a sufficient distance to render the contribution from terrain outside of the model negligible.
- the terrain model is used to predict (forward calculate) the contribution that the terrain made to the total signal over the duration of the survey at a series of regular time intervals
- i is an integer and ⁇ f is the calculation sampling time. At is chosen so that the resolution of the calculated terrain signal exceeds the measurement bandwidth of the instrument. For example, if the bandwidth is 0.5 Hz, the calculation sample time should be less than 1 second.
- the terrain signal is calculated using the principle of superposition where the model is discretised into a set of finite volumes each of which having known mathematical functions to forward calculate the gravity field at a given set of field locations.
- the field points for these calculations are the locations (x(t), y ⁇ t), z( ⁇ ) and possibly the orientations (pitch, roll, yaw) of the instrument interpolated to the time series of equation (1).
- the time series terrain forward calculated data is modified by means of a filter that is designed to mimic the response of the actual measurement.
- the design of this filter is accomplished by incorporating knowledge of the instrument bandwidth and its impulse response.
- An appropriate filter to perform this is a finite impulse response filter mathematically represented by a vector of filter coefficients.
- the filtered forward calculated terrain data then results by simple convolution with the filter.
- bandwidth matched terrain correction data is then resampled onto the time series of the recorded measurements and subtracted from them yielding a new set of raw measurement data ready for subsequent processing.
- the techniques are not restricted to processing gravity data but may also be employed, for example, in processing magnetic field data.
- the measured potential field data may thus be obtained by measuring magnetic field and/or a flux density vector and/or its magnitude, for example using a measurement made with a magnetic gradiometer. If equivalent source elements are used they may then have, for example, a surface current density or a pole strength.
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- Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- General Physics & Mathematics (AREA)
- Mathematical Physics (AREA)
- Ocean & Marine Engineering (AREA)
- Aviation & Aerospace Engineering (AREA)
- Geophysics (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Data Mining & Analysis (AREA)
- Theoretical Computer Science (AREA)
- Mathematical Optimization (AREA)
- Computational Mathematics (AREA)
- Mathematical Analysis (AREA)
- Pure & Applied Mathematics (AREA)
- Databases & Information Systems (AREA)
- Software Systems (AREA)
- General Engineering & Computer Science (AREA)
- Algebra (AREA)
- Geophysics And Detection Of Objects (AREA)
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Abstract
Description
Claims
Priority Applications (5)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US12/449,823 US8359162B2 (en) | 2007-03-23 | 2008-02-21 | Terrain correction systems |
RU2009139072/28A RU2468394C2 (en) | 2007-03-23 | 2008-02-21 | System for adjusting surface topography |
CA002680776A CA2680776A1 (en) | 2007-03-23 | 2008-02-21 | Terrain correction systems |
CN2008800090354A CN101636669B (en) | 2007-03-23 | 2008-02-21 | Terrain correction systems |
AU2008231589A AU2008231589B2 (en) | 2007-03-23 | 2008-02-21 | Terrain correction systems |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB0705605.4 | 2007-03-23 | ||
GB0705605A GB2447699B (en) | 2007-03-23 | 2007-03-23 | Terrain correction systems |
Publications (2)
Publication Number | Publication Date |
---|---|
WO2008117081A2 true WO2008117081A2 (en) | 2008-10-02 |
WO2008117081A3 WO2008117081A3 (en) | 2009-01-08 |
Family
ID=38024709
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/GB2008/050113 WO2008117081A2 (en) | 2007-03-23 | 2008-02-21 | Terrain correction systems |
Country Status (8)
Country | Link |
---|---|
US (1) | US8359162B2 (en) |
CN (1) | CN101636669B (en) |
AU (1) | AU2008231589B2 (en) |
CA (1) | CA2680776A1 (en) |
GB (1) | GB2447699B (en) |
RU (1) | RU2468394C2 (en) |
WO (1) | WO2008117081A2 (en) |
ZA (1) | ZA200905517B (en) |
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2010130967A1 (en) * | 2009-05-15 | 2010-11-18 | Arkex Limited | Geophysical data processing systems |
WO2011098821A2 (en) | 2010-02-12 | 2011-08-18 | Arkex Limited | Geophysical data processing systems |
WO2011148174A2 (en) | 2010-05-28 | 2011-12-01 | Arkex Limited | Processing geophysical data |
WO2012017223A1 (en) | 2010-08-04 | 2012-02-09 | Arkex Limited | Systems and methods for processing geophysical data |
WO2012127210A2 (en) | 2011-03-21 | 2012-09-27 | Arkex Limited | Gravity gradiometer survey techniques |
Families Citing this family (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB2451807B (en) | 2007-08-02 | 2012-01-18 | Arkex Ltd | Geophysical data processing systems |
US9964653B2 (en) | 2011-12-21 | 2018-05-08 | Technoimaging, Llc | Method of terrain correction for potential field geophysical survey data |
CA2881673C (en) | 2012-09-25 | 2020-08-25 | Technological Resources Pty. Limited | A method of processing gravity gradient data |
CN105487129B (en) * | 2016-01-06 | 2017-09-26 | 吉林大学 | A kind of air-ground time domain electromagnetic data altitude correction method |
CN110967778B (en) * | 2019-10-24 | 2021-08-10 | 西北大学 | Dynamic coordinate system polyhedral subdivision gravity grid distribution correction method |
CN113433596B (en) * | 2021-06-25 | 2022-09-16 | 中国船舶重工集团公司第七0七研究所 | Gravity gradient dynamic measurement filtering method based on spatial domain |
CN113985490B (en) * | 2021-09-22 | 2023-05-05 | 中国人民解放军战略支援部队信息工程大学 | Method and device for carrying out surface gravity simulation by utilizing terrain and crust density data |
Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2003032015A1 (en) * | 2001-10-11 | 2003-04-17 | Bhp Billiton Innovation Pty Ltd | Airborne geophysical measurements |
US20060036367A1 (en) * | 2004-08-11 | 2006-02-16 | Bell Geospace Inc. | Method and system for processing geophysical survey data |
Family Cites Families (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4724390A (en) * | 1986-03-24 | 1988-02-09 | Rauscher Elizabeth A | Non-superconducting apparatus for detecting magnetic and electromagnetic fields |
US5112126A (en) * | 1990-07-27 | 1992-05-12 | Chevron Research & Technology Company | Apparatuses and methods for making geophysical measurements useful in determining the deflection of the vertical |
US6614144B2 (en) | 2001-10-04 | 2003-09-02 | Force International, Corp. | Multilayer piezoelectric transformer |
RU2221263C1 (en) | 2002-07-01 | 2004-01-10 | Общество с ограниченной ответственностью Научно-производственное объединение "Петрогаз" | Method and device measuring gravitational field |
RU2254599C1 (en) * | 2003-11-04 | 2005-06-20 | Сорокин Владимир Николаевич | Method of predicting parameters of earthquake |
US7065449B2 (en) * | 2004-03-05 | 2006-06-20 | Bell Geospace, Inc. | Method and system for evaluating geophysical survey data |
US8437960B2 (en) * | 2005-07-27 | 2013-05-07 | Arkex Limited | Gravity survey data processing |
GB2435523B (en) * | 2006-01-25 | 2010-06-23 | Arkex Ltd | Terrain correction systems |
GB2446174B (en) | 2007-01-30 | 2011-07-13 | Arkex Ltd | Gravity survey data processing |
-
2007
- 2007-03-23 GB GB0705605A patent/GB2447699B/en not_active Expired - Fee Related
-
2008
- 2008-02-21 RU RU2009139072/28A patent/RU2468394C2/en not_active IP Right Cessation
- 2008-02-21 CN CN2008800090354A patent/CN101636669B/en not_active Expired - Fee Related
- 2008-02-21 US US12/449,823 patent/US8359162B2/en not_active Expired - Fee Related
- 2008-02-21 CA CA002680776A patent/CA2680776A1/en not_active Abandoned
- 2008-02-21 AU AU2008231589A patent/AU2008231589B2/en not_active Ceased
- 2008-02-21 WO PCT/GB2008/050113 patent/WO2008117081A2/en active Application Filing
- 2008-02-21 ZA ZA200905517A patent/ZA200905517B/en unknown
Patent Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2003032015A1 (en) * | 2001-10-11 | 2003-04-17 | Bhp Billiton Innovation Pty Ltd | Airborne geophysical measurements |
US20060036367A1 (en) * | 2004-08-11 | 2006-02-16 | Bell Geospace Inc. | Method and system for processing geophysical survey data |
Non-Patent Citations (3)
Title |
---|
HAMMER S: "Topographic and terrain correction for airborne gravity" GEOPHYSICS USA, vol. 39, no. 4, August 1974 (1974-08), pages 537-542, XP002502770 ISSN: 0016-8033 * |
LI Y C ET AL: "Improved gravimetric terrain corrections" GEOPHYSICAL JOURNAL INTERNATIONAL UK, vol. 119, no. 3, December 1994 (1994-12), pages 740-752, XP002502769 ISSN: 0956-540X * |
PERPARIM AMETI: "Downward continuation of geopotential in Switzerland"[Online] 2006, pages O-122, XP002502768 Darmstadt Retrieved from the Internet: URL:http://tuprints.ulb.tu-darmstadt.de/epda/000671/ameti_thesis.pdf> [retrieved on 2008-11-05] * |
Cited By (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2010130967A1 (en) * | 2009-05-15 | 2010-11-18 | Arkex Limited | Geophysical data processing systems |
CN102428393A (en) * | 2009-05-15 | 2012-04-25 | 阿克斯有限责任公司 | Geophysical data processing systems |
AU2009346196B2 (en) * | 2009-05-15 | 2014-04-24 | Arkex Limited | Geophysical data processing systems |
WO2011098821A2 (en) | 2010-02-12 | 2011-08-18 | Arkex Limited | Geophysical data processing systems |
WO2011148174A2 (en) | 2010-05-28 | 2011-12-01 | Arkex Limited | Processing geophysical data |
WO2012017223A1 (en) | 2010-08-04 | 2012-02-09 | Arkex Limited | Systems and methods for processing geophysical data |
WO2012127210A2 (en) | 2011-03-21 | 2012-09-27 | Arkex Limited | Gravity gradiometer survey techniques |
Also Published As
Publication number | Publication date |
---|---|
US20100094556A1 (en) | 2010-04-15 |
GB2447699A (en) | 2008-09-24 |
CN101636669A (en) | 2010-01-27 |
CN101636669B (en) | 2012-11-21 |
WO2008117081A3 (en) | 2009-01-08 |
RU2468394C2 (en) | 2012-11-27 |
ZA200905517B (en) | 2010-10-27 |
RU2009139072A (en) | 2011-04-27 |
US8359162B2 (en) | 2013-01-22 |
GB2447699B (en) | 2011-07-13 |
CA2680776A1 (en) | 2008-10-02 |
GB0705605D0 (en) | 2007-05-02 |
AU2008231589A1 (en) | 2008-10-02 |
AU2008231589B2 (en) | 2013-02-21 |
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