Георадар ( GPR ) - это геофизический метод, который использует радиолокационные импульсы для изображения недр. Это неинтрузивный метод исследования недр для исследования подземных коммуникаций, таких как бетон, асфальт, металлы, трубы, кабели или кладка. [1] В этом неразрушающем методе используется электромагнитное излучение в микроволновом диапазоне ( частоты UHF / VHF ) радиочастотного спектра., и обнаруживает отраженные сигналы от подземных структур. Георадар может применяться в различных средах, включая камни, почву, лед, пресную воду, тротуары и конструкции. В правильных условиях практикующие врачи могут использовать георадар для обнаружения подземных объектов, изменений свойств материала, пустот и трещин. [2]
В георадаре используются высокочастотные (обычно поляризованные) радиоволны, обычно в диапазоне от 10 МГц до 2,6 ГГц. Передатчик и антенна георадара излучают электромагнитную энергию в землю. Когда энергия встречает заглубленный объект или границу между материалами, имеющими разную диэлектрическую проницаемость , она может отражаться, преломляться или рассеиваться обратно на поверхность. Приемная антенна может записывать изменения в обратном сигнале. Используемые принципы аналогичны сейсмологии , за исключением того, что методы георадара реализуют электромагнитную энергию, а не акустическую энергию, и энергия может отражаться на границах, где изменяются подземные электрические свойства, а не подземные механические свойства, как в случае с сейсмической энергией.
Электропроводность земли, передаваемый центр частоты , а мощность излучения все может ограничить эффективный диапазон глубины исследования GPR. Увеличение электропроводности ослабляет введенную электромагнитную волну, и, таким образом, глубина проникновения уменьшается. Из-за частотно-зависимых механизмов затухания более высокие частоты не проникают так далеко, как более низкие частоты. Однако более высокие частоты могут обеспечить улучшенное разрешение . Таким образом, рабочая частота всегда является компромиссом между разрешением и проникновением. Оптимальная глубина подземного проникновения достигается во льдах, где глубина проникновения может достигать нескольких тысяч метров (до коренных пород в Гренландии) при низких частотах георадара. Сухие песчаные почвы или массивные сухие материалы, такие как гранит , известняк и бетон, имеют тенденцию быть резистивными, а не проводящими, а глубина проникновения может достигать 15 метров (49 футов). Однако во влажных или глинистых почвах и материалах с высокой электропроводностью проникновение может составлять всего несколько сантиметров.
Антенны георадаров обычно соприкасаются с землей для обеспечения максимальной мощности сигнала; тем не менее, антенны георадара, запускаемые с воздуха, могут использоваться и над землей.
Георадиолокация между скважинами была разработана в области гидрогеофизики как ценное средство оценки наличия и количества почвенной воды .
История
The first patent for a system designed to use continuous-wave radar to locate buried objects was submitted by Gotthelf Leimbach and Heinrich Löwy in 1910, six years after the first patent for radar itself (patent DE 237 944). A patent for a system using radar pulses rather than a continuous wave was filed in 1926 by Dr. Hülsenbeck (DE 489 434), leading to improved depth resolution. A glacier's depth was measured using ground penetrating radar in 1929 by W. Stern.[3]
Further developments in the field remained sparse until the 1970s, when military applications began driving research. Commercial applications followed and the first affordable consumer equipment was sold in 1975.[3]
In 1972 the Apollo 17 mission carried a ground penetrating radar called ALSE (Apollo Lunar Sounder Experiment) in orbit around the Moon. It was able to record depth information up to 1.3 km and recorded the results on film due to the lack of suitable computer storage at the time.[4]
Applications
GPR has many applications in a number of fields. In the Earth sciences it is used to study bedrock, soils, groundwater, and ice. It is of some utility in prospecting for gold nuggets and for diamonds in alluvial gravel beds, by finding natural traps in buried stream beds that have the potential for accumulating heavier particles.[5] The Chinese lunar rover Yutu has a GPR on its underside to investigate the soil and crust of the Moon.
Engineering applications include nondestructive testing (NDT) of structures and pavements, locating buried structures and utility lines, and studying soils and bedrock. In environmental remediation, GPR is used to define landfills, contaminant plumes, and other remediation sites, while in archaeology it is used for mapping archaeological features and cemeteries. GPR is used in law enforcement for locating clandestine graves and buried evidence. Military uses include detection of mines, unexploded ordnance, and tunnels.
Borehole radars utilizing GPR are used to map the structures from a borehole in underground mining applications. Modern directional borehole radar systems are able to produce three-dimensional images from measurements in a single borehole.[6]
One of the other main applications for ground-penetrating radars is for locating underground utilities. Standard electromagnetic induction utility locating tools require utilities to be conductive. These tools are ineffective for locating plastic conduits or concrete storm and sanitary sewers. Since GPR detects variations in dielectric properties in the subsurface, it can be highly effective for locating non-conductive utilities.
GPR was often used on the Channel 4 television programme Time Team which used the technology to determine a suitable area for examination by means of excavations. In 1992 GPR was used to recover £150,000 in cash that kidnapper Michael Sams received as a ransom for an estate agent he had kidnapped after Sams buried the money in a field.[7]
Archaeology
Ground penetrating radar survey is one method used in archaeological geophysics. GPR can be used to detect and map subsurface archaeological artifacts, features, and patterning.[8]
The concept of radar is familiar to most people. With ground penetrating radar, the radar signal – an electromagnetic pulse – is directed into the ground (it is important to not get GPR surveys confused with electromagnetic surveys, a recent survey of an Iron Age hillfort in Hampshire recently revealed the discrepancies between Magnetometry, EM and GPR surveys over the same area). Subsurface objects and stratigraphy (layering) will cause reflections that are picked up by a receiver. The travel time of the reflected signal indicates the depth. Data may be plotted as profiles, as planview maps isolating specific depths, or as three-dimensional models.
GPR can be a powerful tool in favorable conditions (uniform sandy soils are ideal). Like other geophysical methods used in archaeology (and unlike excavation) it can locate artifacts and map features without any risk of damaging them. Among methods used in archaeological geophysics, it is unique both in its ability to detect some small objects at relatively great depths, and in its ability to distinguish the depth of anomaly sources.
The principal disadvantage of GPR is that it is severely limited by less-than-ideal environmental conditions. Fine-grained sediments (clays and silts) are often problematic because their high electrical conductivity causes loss of signal strength; rocky or heterogeneous sediments scatter the GPR signal, weakening the useful signal while increasing extraneous noise.
In the field of cultural heritage GPR with high frequency antenna is also used for investigating historical masonry structures, detecting cracks and decay patterns of columns and detachment of frescoes.[9]
Military
Military applications of ground-penetrating radar include detection of unexploded ordnance and detecting tunnels. In military applications and other common GPR applications, practitioners often use GPR in conjunction with other available geophysical techniques such as electrical resistivity and electromagnetic induction methods.
In May 2020, the U.S. military ordered ground-penetrating radar system from Chemring Sensors and Electronics Systems (CSES), to detect improvised explosive devices (IEDs) buried in roadways, in $200.2 million deal.[10]
Vehicle localization
A recent novel approach to vehicle localization using prior map based images from ground penetrating radar has been demonstrated. Termed "Localizing Ground Penetrating Radar" (LGPR), centimeter level accuracies at speeds up to 60 mph have been demonstrated.[11] Closed-loop operation was first demonstrated in 2012 for autonomous vehicle steering and fielded for military operation in 2013.[11] Highway speed centimeter-level localization during a night-time snow-storm was demonstrated in 2016.[12][13]
Three-dimensional imaging
Individual lines of GPR data represent a sectional (profile) view of the subsurface. Multiple lines of data systematically collected over an area may be used to construct three-dimensional or tomographic images. Data may be presented as three-dimensional blocks, or as horizontal or vertical slices. Horizontal slices (known as "depth slices" or "time slices") are essentially planview maps isolating specific depths. Time-slicing has become standard practice in archaeological applications, because horizontal patterning is often the most important indicator of cultural activities.[14]
Limitations
The most significant performance limitation of GPR is in high-conductivity materials such as clay soils and soils that are salt contaminated. Performance is also limited by signal scattering in heterogeneous conditions (e.g. rocky soils).
Other disadvantages of currently available GPR systems include:
- Interpretation of radar-grams is generally non-intuitive to the novice.
- Considerable expertise is necessary to effectively design, conduct, and interpret GPR surveys.
- Relatively high energy consumption can be problematic for extensive field surveys.
Radar is sensitive to changes in material composition, detecting changes requires movement. When looking through stationary items using surface-penetrating or ground-penetrating radar, the equipment needs to be moved in order for the radar to examine the specified area by looking for differences in material composition. While it can identify items such as pipes, voids, and soil, it cannot identify the specific materials, such as gold and precious gems. It can however, be useful in providing subsurface mapping of potential gem-bearing pockets, or "vugs." The readings can be confused by moisture in the ground, and they can't separate gem-bearing pockets from the non-gem-bearing ones.[15]
When determining depth capabilities, the frequency range of the antenna dictates the size of the antenna and the depth capability. The grid spacing which is scanned is based on the size of the targets that need to be identified and the results required. Typical grid spacings can be 1 meter, 3 ft, 5 ft, 10 ft, 20 ft for ground surveys, and for walls and floors 1 inch–1 ft.
The speed at which a radar signal travels is dependent upon the composition of the material being penetrated. The depth to a target is determined based on the amount of time it takes for the radar signal to reflect back to the unit’s antenna. Radar signals travel at different velocities through different types of materials. It is possible to use the depth to a known object to determine a specific velocity and then calibrate the depth calculations.
Power regulation
In 2005, the European Telecommunications Standards Institute introduced legislation to regulate GPR equipment and GPR operators to control excess emissions of electromagnetic radiation.[16] The European GPR association (EuroGPR) was formed as a trade association to represent and protect the legitimate use of GPR in Europe.
Similar technologies
Ground-penetrating radar uses a variety of technologies to generate the radar signal: these are impulse,[17] stepped frequency, frequency-modulated continuous-wave (FMCW), and noise. Systems on the market in 2009 also use Digital signal processing (DSP) to process the data during survey work rather than off-line.
A special kind of GPR uses unmodulated continuous-wave signals. This holographic subsurface radar differs from other GPR types in that it records plan-view subsurface holograms. Depth penetration of this kind of radar is rather small (20–30 cm), but lateral resolution is enough to discriminate different types of landmines in the soil, or cavities, defects, bugging devices, or other hidden objects in walls, floors, and structural elements.[18][19]
GPR is used on vehicles for close-in high-speed road survey and landmine detection as well as in stand-off mode.[definition needed]
In Pipe-Penetrating Radar (IPPR) and In Sewer GPR (ISGPR) are applications of GPR technologies applied in non-metallic-pipes where the signals are directed through pipe and conduit walls to detect pipe wall thickness and voids behind the pipe walls.[20][21][22]
Wall-penetrating radar can read through non-metallic structures as demonstrated for the first time by ASIO and Australian Police in 1984 while surveying an ex Russian Embassy in Canberra. Police showed how to watch people up to two rooms away laterally and through floors vertically, could see metal lumps that might be weapons; GPR can even act as a motion sensor for military guards and police.
SewerVUE Technology, an advanced pipe condition assessment company utilizes Pipe Penetrating Radar (PPR) as an in pipe GPR application to see remaining wall thickness, rebar cover, delamination, and detect the presence of voids developing outside the pipe.
The "Mineseeker Project" seeks to design a system to determine whether landmines are present in areas using ultra wideband synthetic aperture radar units mounted on blimps.
References
- ^ "How Ground Penetrating Radar Works". Tech27.
- ^ Daniels DJ (ed.) (2004). Ground Penetrating Radar (2nd ed.). Knoval (Institution of Engineering and Technology). pp. 1–4. ISBN 978-0-86341-360-5.CS1 maint: extra text: authors list (link)
- ^ a b "History of Ground Penetrating Radar Technology". Ingenieurbüro obonic. Archived from the original on 2 February 2017. Retrieved 13 February 2016.
- ^ "The Apollo Lunar Sounder Radar System" - Proceedings of the IEEE, June 1974
- ^ Wilson, M. G. C.; Henry, G.; Marshall, T. R. (2006). "A review of the alluvial diamond industry and the gravels of the North West Province, South Africa" (PDF). South African Journal of Geology. 109 (3): 301–314. doi:10.2113/gssajg.109.3.301. Archived (PDF) from the original on 5 July 2013. Retrieved 9 December 2012.
- ^ Hofinghoff, Jan-Florian (2013). "Resistive Loaded Antenna for Ground Penetrating Radar Inside a Bottom Hole Assembly". IEEE Transactions on Antennas and Propagation. 61 (12): 6201–6205. Bibcode:2013ITAP...61.6201H. doi:10.1109/TAP.2013.2283604. S2CID 43083872.
- ^ Birmingham Mail
- ^ Lowe, Kelsey M; Wallis, Lynley A.; Pardoe, Colin; Marwick, Benjamin; Clarkson, Christopher J; Manne, Tiina; Smith, M.A.; Fullagar, Richard (2014). "Ground-penetrating radar and burial practices in western Arnhem Land, Australia". Archaeology in Oceania. 49 (3): 148–157. doi:10.1002/arco.5039.
- ^ Masini, N; Persico, R; Rizzo, E (2010). "Some examples of GPR prospecting for monitoring of the monumental heritage". Journal of Geophysics and Engineering. 7 (2): 190. Bibcode:2010JGE.....7..190M. doi:10.1088/1742-2132/7/2/S05.
- ^ "Army orders ground-penetrating radar system from CSES for detecting hidden IEDs in $200.2 million deal". Military & Aerospace Electronics. 13 May 2020.
- ^ a b Cornick, Matthew; Koechling, Jeffrey; Stanley, Byron; Zhang, Beijia (1 January 2016). "Localizing ground penetrating RADAR: A step toward robust autonomous ground vehicle localization". Journal of Field Robotics. 33 (1): 82–102. doi:10.1002/rob.21605. ISSN 1556-4967.
- ^ Enabling autonomous vehicles to drive in the snow with localizing ground penetrating radar (video). MIT Lincoln Laboratory. 24 June 2016. Archived from the original on 19 January 2017. Retrieved 31 May 2017 – via YouTube.
- ^ "MIT Lincoln Laboratory: News: Lincoln Laboratory demonstrates highly accurate vehicle localization under adverse weather conditions". www.ll.mit.edu. Archived from the original on 31 May 2017. Retrieved 31 May 2017.
- ^ Conyers, Lawrence B. And Dean Goodman 1997 Ground Penetrating Radar: An Introduction for Archaeologists. Walnut Creek, CA.: Altamira Press
- ^ "Gems and Technology – Vision Underground". The Ganoksin Project. Archived from the original on 22 February 2014. Retrieved 5 February 2014.
- ^ Electromagnetic compatibility and Radio spectrum Matters (ERM). Code of Practice in respect of the control, use and application of Ground Probing Radar (GPR) and Wall Probing Radar (WPR) systems and equipment. European Telecommunications Standards Institute. September 2009. ETSI EG 202 730 V1.1.1.
- ^ "An impulse generator for the ground penetrating radar" (PDF). Archived (PDF) from the original on 18 April 2015. Retrieved 25 March 2013.
- ^ Zhuravlev, A.V.; Ivashov, S.I.; Razevig, V.V.; Vasiliev, I.A.; Türk, A.S.; Kizilay, A. (2013). Holographic subsurface imaging radar for applications in civil engineering (PDF). IET International Radar Conference. Xi'an, China: IET. doi:10.1049/cp.2013.0111. Archived (PDF) from the original on 29 September 2013. Retrieved 26 September 2013.
- ^ Ivashov, S. I.; Razevig, V. V.; Vasiliev, I. A.; Zhuravlev, A. V.; Bechtel, T. D.; Capineri, L. (2011). "Holographic Subsurface Radar of RASCAN Type: Development and Application" (PDF). IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing. 4 (4): 763–778. Bibcode:2011IJSTA...4..763I. doi:10.1109/JSTARS.2011.2161755. S2CID 12663279. Archived (PDF) from the original on 29 September 2013. Retrieved 26 September 2013.
- ^ "Ground Penetrating Radar(GPR) Systems – Murphysurveys". www.murphysurveys.co.uk. Archived from the original on 10 September 2017. Retrieved 10 September 2017.
- ^ Ékes, C.; Neducza, B.; Takacs, P. (2014). Proceedings of the 15th International Conference on Ground Penetrating Radar. pp. 368–371. doi:10.1109/ICGPR.2014.6970448. ISBN 978-1-4799-6789-6. S2CID 22956188.
- ^ "International No-Dig Meets in Singapore - Trenchless Technology Magazine". Trenchless Technology Magazine. 30 December 2010. Retrieved 10 September 2017.
- Borchert, Olaf (2008). "Receiver Design for a Directional Borehole Radar System (dissertation)". University of Wuppertal.
Further reading
An overview of scientific and engineering applications can be found in:
- Jol, H. M., ed. (2008). Ground Penetrating Radar Theory and Applications. Elsevier.
- Persico, Raffaele (2014). Introduction to ground penetrating radar: inverse scattering and data processing. John Wiley & Sons.
A general overview of geophysical methods in archaeology can be found in the following works:
- Clark, Anthony J. (1996). Seeing Beneath the Soil. Prospecting Methods in Archaeology. London, United Kingdom: B.T. Batsford Ltd.
- Conyers, L. B. (2004). Ground-penetrating Radar for Archaeology. Walnut Creek, CA., United States: AltaMira Press Ltd.
- Gaffney, Chris; John Gater (2003). Revealing the Buried Past: Geophysics for Archaeologists. Stroud, United Kingdom: Tempus.
External links
- "EUROGPR – The European GPR regulatory body".
- "GprMax – GPR numerical simulator based on the FDTD method".
- "Short movie showing acquisition, processing and accuracy of GPR readings". Youtube.
- "FDTD Animation of sample GPR propagation". Youtube.
- "GPR Electromagnetic Emissions Safety Information". 17 May 2016.