GPR 용어 사전
| 용어 | 일반 기호 | 일반적인 단위 | 설명 |
|---|---|---|---|
| 3 dB 대역폭 | MHz 또는 GHz | GPR 신호의 진폭이 (최대 진폭 / √2)와 같은 값을 초과하는 주파수 스펙트럼의 범위 | |
| 3D 보기 | 시간 또는 깊이 또는 시간 차원을 가진 표면 영역을 표시할 때 사용되는 용어. 데이터는 복셀(작은 큐브 모양의 볼륨)로 나누어지고 데이터 값은 3D 볼륨의 교차 단면 슬라이스 또는 가변 투명도를 렌더링하는 도구로 표시됩니다. | ||
| 6 dB 대역폭 | MHz 또는 GHz | GPR 신호의 진폭이 (최대 진폭 / 2)와 같은 값을 초과하는 주파수 스펙트럼의 범위 | |
| 수집 모드 | GPR 추적 수집을 시작하는 방법을 설명하는 용어. 일반적인 방법은 다음과 같습니다: 거리 - 추적 수집은 공간 위치(일반적으로 등간격의 단계)에서 발생하며 위치는 오도미터 또는 기타 거리 측정 장치에서 결정됩니다. 자유 실행 - 추적은 시스템이 허용하는 한 빠르게 연속적으로 수집됩니다. 시간 - 추적 수집은 이전 추적 수집 완료 후 정의된 시간 간격 또는 지연 시간에 의해 제어됩니다. 외부 트리거 - 추적 수집은 수동 버튼 누르기 또는 전자 입력 신호와 같은 외부 트리거에 의해 제어됩니다. | ||
| 집합체 | 혼합에 사용되는 모든 경질의 비활성 광물 재료. 모래, 자갈, 부순 돌, 또는 슬래그가 포함됩니다. 주로 콘크리트나 아스팔트 생성에 사용되는 재료입니다. | ||
| 공기 파동 | GPR 시스템은 송신기에서 모든 방향으로 이동하는 전자기 주파수 에너지를 방출하고 수신기는 모든 방향에서 이를 수신합니다. GPR은 지하 신호를 감지하는 데 사용됩니다. 지면 위를 이동하며 지면 위의 물체에서 반사되는 GPR 신호는 원하지 않는 일관된 잡음 신호인 공기 파동을 생성합니다. | ||
| 안테나 | 전기 신호를 전파되는 전자기파로 변환하는 장치. GPR에서는 보통 송신 안테나와 수신 안테나가 있습니다. 송수신 전자 장치와 결합되면 변환기라는 용어가 사용됩니다 (변환기 참조). | ||
| 안테나 분리 | GPR은 보통 송신과 수신을 위해 별도의 안테나를 사용합니다. 안테나들의 물리적 중심 간의 선형 거리를 안테나 분리라고 합니다. | ||
| 배열 | 송신 안테나와 수신 안테나가 여러 개 배치되어 있으며 각 요소의 고정된 공간 위치가 정의된 고급 GPR 시스템에서 사용되는 용어입니다. | ||
| 감쇠 | α | 네퍼 또는 dB/m | 전파되는 신호의 진폭이 매체 내에서 에너지 소산에 의해 감소하는 현상을 나타내는 용어입니다. GPR에서는 감쇠가 일반적으로 매체의 전기 전도도와 관련이 있습니다. |
| 자동 이득 제어 | AGC | GPR 신호의 진폭을 평등하게 하기 위해 신호 강도에 반비례하는 이득을 적용하는 이득 함수. 이 유형의 이득은 반사 이벤트의 연속성을 정의하는 데 가장 유용합니다. | |
| 평균 주파수 스펙트럼 | AFS | GPR 데이터 파일 또는 구간 내에서 모든 진폭 스펙트럼을 계산하고 평균화하는 과정을 설명하는 용어입니다. 이 플롯은 신호의 주파수 내용을 보여주므로 주파수 필터링 매개변수를 결정하는 데 자주 사용됩니다. 예를 들어 밴드패스 필터를 적용할 수 있습니다. | |
| 평균 트레이스 진폭 | ATA | 전체 GPR 라인에 대해 평균 정류 신호 진폭을 표시하는 플롯입니다. 이 플롯은 GPR 신호 진폭이 얼마나 빠르게 감쇠되는지 표시하고 주변 소음 수준을 평가하는 강력한 방법으로 입증되었습니다. 또한 GPR 신호 침투의 최대 깊이를 추정하는 데 도움이 됩니다. | |
| 배경 평균 빼기 | BAS | GPR 데이터 세트의 모든 트레이스의 평균을 계산한 후, 이 평균 트레이스를 데이터 세트의 모든 트레이스에서 빼는 과정입니다. 대부분은 GPR 이미지에서 일정한 밴드로 나타나는 일관된 시스템 소음을 억제하기 위해 품질이 낮은 GPR 데이터에서 사용됩니다. 이 과정은 지점 목표로부터 나온 하이퍼볼라와 같은 약한 공간적 변화를 더 잘 볼 수 있도록 하며, GPR 라인에 공통으로 나타나는 시간 상수 응답을 제거합니다. 또한, 시간 제로에서 보이는 직접 공기 및 직접 지면 파동(송신 펄스)을 제거하는 데 사용됩니다. | |
| 배경 빼기 | BSUB | 이 과정은 배경 평균 빼기와 유사하지만, 개별 처리된 트레이스를 중심으로 한 국소적인 트레이스 집합에 대한 실행 평균을 사용하여 배경 평균 트레이스를 구하고 빼는 방법입니다. 이 과정은 지점 목표에서 나온 하이퍼볼라와 같은 국소적인 이벤트를 강화하고 수평 또는 천천히 변하는 이벤트를 억제합니다. 이는 평탄하게 놓인 국소 이벤트를 제거하는 데 매우 유용할 수 있습니다. 또한, 시간 제로에서 보이는 직접 공기 및 직접 지면 파동(송신 펄스)을 억제하는 데 사용됩니다. | |
| 밴드패스 필터 | 주어진 GPR 데이터에서 주파수 범위를 유지하고 다른 모든 주파수를 억제하는 과정입니다. GPR은 초광대역 기록 장치로, GPR 송신기가 생성하지 않은 노이즈 신호를 포함할 수 있습니다. 유지할 주파수와 억제할 주파수를 신중하게 선택하면 GPR 이미지의 해석 가능성을 향상시킬 수 있습니다. 밴드패스 필터링은 주로 푸리에 분석과 스펙트럼 가중치를 통해 이루어지지만, 적절한 시간 필터 임펄스 응답과 함께 GPR 신호의 시간 컨볼루션을 통해서도 수행될 수 있습니다. | ||
| 대역폭 | 주어진 장치가 신호를 송수신할 때 특정 진폭 또는 전력 이상으로 송수신하는 주파수 범위. | ||
| 중심 주파수 | 초광대역 장치에 대해 구체적으로 정의된 용어입니다. 신호 진폭(예: 3dB 대역폭)에 대한 상한선과 하한선이 정의됩니다. 상한선과 하한선의 평균값을 중심 주파수로 정의합니다. 중심 주파수는 GPR 시스템에서 스펙트럼 진폭이 최대가 되는 주파수와 매우 근접한 경우가 많습니다. 그 결과, 최대 주파수와 중심 주파수 용어는 종종 교환하여 사용되지만, 이는 정확히 맞지 않습니다. | ||
| 채널 | 단일 TX-RX 안테나 쌍에서 생성된 GPR 신호를 설명하는 데 사용되는 용어로, 고정된 주파수, 분리, 방향성 등과 같은 매개변수를 가집니다. (배열 요소 정의도 참조하십시오.) | ||
| 색상 바 | 색상 팔레트를 표시하는 색상의 바로, 일반적으로 색상 이미지에서 특정 색상으로 표시된 데이터 값 범위(일반적으로 GPR 신호 진폭)를 표시하는 레이블이 붙어 있습니다. | ||
| 색상 팔레트 | 데이터 값을 색상에 매핑하는 과정을 설명하는 용어입니다. 색상 테이블이라고도 합니다. GPR에서 주로 교차 단면도, 깊이 또는 시간 슬라이스 이미지, 3D 이미지 생성 시 데이터 속성(예: 진폭)을 색상에 할당하는 데 사용됩니다. | ||
| 공통 중간점 | CMP | 공통 중간점(CMP)은 송신기와 수신기 안테나 위치가 변하지만 중간점이 일정하게 유지되도록 이동하는 GPR 조사 유형입니다. | |
| 공통 오프셋 반사 구성 | COR | 위치에서 위치로 이동하는 고정된 안테나 기하학으로 데이터를 수집할 때 사용되는 용어입니다. 대부분 송신기와 수신기 안테나의 방향과 분리가 고정됩니다. 또한 라인 프로파일링을 참조하십시오. | |
| 동시 수신기 운영 | 여러 수신기가 동시에 데이터 샘플을 획득할 때 사용되는 용어입니다. 데이터 수집은 모든 수신기가 송신기 펄스 발사 후 동시에 데이터를 수집하도록 동기화됩니다. 개별 수신기의 타이밍 정확도는 성공적인 데이터 수집을 위해 수십 피코초 수준이어야 합니다. 이는 역사적인 다중 수신기 운영에 비해 GPR 데이터 수집 속도를 크게 향상시킵니다. | ||
| 전도도 | σ | milliSiemens/meter 또는 mS/m 또는 millimhos/m (역사적) | 재료가 전류를 전도하는 능력입니다. 등방성 재료에서 이는 저항률의 역수입니다. 때때로 특정 전도도라고도 불립니다. |
| 단면도 | 인접한 공간 측정 위치에서의 여러 트레이스를 나란히 표시하여 얻은 이미지입니다. | ||
| 데시벨 | dB | 비율을 20 log10 형식으로 표현하는 데 사용되는 단위입니다. 10의 비율은 20 데시벨에 해당합니다. | |
| 깊이 가변 이득 | 깊이에 따라 변화하는 곱셈 인자에 적용되는 용어입니다. 목적은 깊이에 따른 신호 진폭의 상대적 변화를 변경하는 것입니다. 또한 시간 가변 이득을 참조하십시오. | ||
| 깊이 또는 단면 이미지 | GPR 데이터 트레이스를 나란히 플로팅하여 지면 이미지를 만들 때 사용되는 용어이며, 수직 축은 깊이를 나타내며, 이는 신호 이동 시간을 깊이로 변환하여 얻은 값입니다. 이 용어는 종종 깊이 단면 또는 단면으로 축약됩니다. | ||
| 깊이 슬라이스(이미지) | 데이터 볼륨을 통해 슬라이스를 렌더링하여 색상 또는 등고선 표시로 얻은 이미지를 설명하는 용어입니다. 일반적으로 컴퓨터 프로세스를 통해 생성됩니다. 이 용어는 일반적으로 깊이 슬라이스로 축약됩니다. | ||
| 디와우 | GPR 데이터에서 매우 낮은 주파수 성분을 제거하는 과정입니다. 이러한 저주파 성분은 유도 현상 또는 가능한 기기 동적 범위 제한과 관련이 있습니다. GPR 트레이스의 기준선이 천천히 위아래로 진동하는 현상은 GPR 초기에는 "와우"라고 불렸습니다. 이 효과를 제거하는 과정을 "디와우"라고 부르게 되었습니다. | ||
| dielectric constant | K | See dielectric permittivity. | |
| dielectric permittivity | K | A fundamental physical property that describes the electrical polarizability of a material. Free space or vacuum has a permittivity of 8.89 x10-12 Fd/m. Most often the term is applied to the relative dielectric permittivity where the material permittivity is divided by the free space permittivity. Most natural materials have a relative permittivity in the range of 1 -80 in the radio frequency range. The dielectric permittivity is often referred to as relative permittivity or dielectric constant. | |
| display unit | The term applied to a device that controls, records and displays the GPR data. This device is sometimes a personal computer (PC) but can also be a custom-built, fit-for-purpose computer system (see digital video logger DVL). | ||
| distance measuring instrument | DMI | A device for accurately measuring elapsed distances along a survey line or transect. The term is common in roadway surveys to measure longitudinal distance from an intersection or other visible geographic location. See also odometer. In GPR applications the output of the device may be used to trigger the acquisition of GPR at fixed distance (step) intervals. | |
| DynaQ | DynaQ | is an advanced, GPRLine-patented technology that dynamically adjusts stacking as system movement speed varies. Stacking is a means of improving signal to noise so being able to adapt the stacking to sensor movement speed creates a dynamic quality data acquisition technique. | |
| electromagnetic | EM | is the term applied to methods which use electric and magnetic fields to transmit signals or make sensing observations. The term is a general one that encompasses the whole field of science involved in electric and magnetic fields – particularly when the fields are time varying and therefore coupled. | |
| envelope | formed from a pair of traces that uniquely bracket the extremes of an oscillatory signal. The signal is assumed to have a zero average or base line, so the upper and lower traces are identical but of opposite sign. The envelope is obtained by using the method referred to as the Hilbert transform to calculate the positive and negative traces; the positive bounding trace is normally referred to as ‘the envelope’. The envelope does not have the oscillatory nature of the original signal. The envelope is more indicate of the data resolution. Enveloping can also simplify the GPR section display making it easier to interpret. Creating depth slices of the envelope is a powerful way of displaying GPR data that cover an area. | ||
| falling weight deflectometer | FWD | A non-destructive testing device that is used to perform structural testing for pavement rehabilitation projects, research, and pavement structure failure detection. It is used for conventional and deep-strength flexible, composite and rigid pavement structures. The FWD applies a dynamic load to the pavement surface, similar in magnitude and duration to that of a single heavy moving wheel load. The response of the pavement system is measured in terms of vertical deformation, or deflection, using seismometers. | |
| file size | bytes | The actual or physical limit on the amount of data stored in a computer file. | |
| first break time | Time of onset of the direct air signal at the GPR receiver, referenced to the start time of trace recoding. When plotting GPR data this time offset establishes the zero point on the time scale axis. In practice, this offset time on a GPR trace is determined by sensing when the receiver signal rises above a defined level for the first time from start of recording. | ||
| frequency | f | Hz, MHz, GHz | is the term applied when a signal is repetitive at regular intervals of time. Frequency measures the number of repetitions that occur in a time interval such as pulse per second or cycles per second. (Frequency can also be used in other contexts such as spatial frequency which indicates a signal that repeats with distance or length such as cycles per meter). The term is also used to indicate the center or peak frequency of a GPR antenna response although it is somewhat a mis-use of the term. |
| Fresnel zone | For a reflection from a surface, there is a finite area on the surface for which signals travelling from the source to the receiver are indistinguishable based on the time of travel or length of travel path. This area is defined to be the Fresnel zone or zone of influence. The Fresnel zone is defined by differences in path length being a faction of the wavelength when the signal is sinusoidal excitation. The zone of influence is the same concept but expressed in terms of differences in travel time being less than a fraction of the pulse-width of an impulsive transient signal. | ||
| gain | Process of amplifying signals to match recording device or the dynamic range of the display. See time gain. | ||
| global positioning system | GPS | GPS is a satellite-based approach to obtaining georeferenced coordinates. The satellites transit a defined timing signal and the GPR receiver, usually on or near the Earth’s surface, records the signals from many satellites and uses the signals to triangulate the best estimate of the receiver location in 3D space with reference to a standard earth geoid shape. The result is normally latitude and longitude and elevation as well as a very precise time. | |
| GPS Files | When GPS is used with GPR, the GPS receiver data is recorded in a data file and recorded information tied to the GPR data. When the GPS record is available and synced to the GPR data, Latitude and Longitude, UTM coordinates, and GPS elevation can be provided for every GPR trace in a data set. A GPS file is created by attaching a GPS system to the GPR system during data collection. GPS files contain lines of standard GPS positional output text (called NMEA strings) and the associated GPR trace number. When the GPS file is attached, latitude, longitude, and GPS elevations for every GPR trace can be saved into the GPR file. | ||
| GPZ | .gpz | A .gpz file is a GPRLine standard data file for GPR data recording and interchange. The .gpz is used with the PC-based GPR software called EKKO_Project. The .gpz file contains a wide variety of data files including GPS files and .dt1 GPR data files as well as proprietary data from GPRLine instruments and auxiliary sensors. | |
| Grid | A square or rectilinear set of straight lines which cover an area. Acquiring data on a grid means acquiring data along each line forming the grid. Acquiring data on a grid at regular spatial steps is the optimal way to obtain a data set suitable for advance signal processing, such as the creation of 3D volume renderings and depth or time slice images. Conventional notation is to use a first quadrant Cartesian coordinate system with X and Y axes. | ||
| Grid Resolution | is the term used to describe the XY spatial resolution attained in a grid and is controlled by the largest line or trace spacing. | ||
| grid size | term used to describe a real extent of a rectilinear grid (i.e. 5m x 10m, 20ft x 50ft., 24″ x 24″, 600 mm x 600mm). | ||
| grid survey | is the term to describe the process of acquiring data on a grid over an area with the end goal to create 3D, depth or time slice images. | ||
| ground-penetrating radar | GPR | Ground penetrating radar is a geophysical method for mapping subsurface structure using electromagnetic energy. There are several deployment methods, but all approaches involve a transmitter creating radio frequency signals typically in the 1 to 5000 MHz frequency range and a receiver which detects similar signals. The goal is to measure the impulse response or the transfer function of the surrounding medium with the view of reconstructing the material property structure. In its simplest form, a GPR system with a transmitter and receiver are moved over the ground surface and reflections returning from subsurface objects are detected, recorded and displayed to the user. | |
| herring bone effect | Term applied to distortion in a map image derived from a grid survey when there are measurement system errors. The effect is most pronounced when data are collected in alternating directions along grid lines with an improperly calibrated odometer. In the case of GPS or similar positioning techniques, the systematic positioning error can be created by a finite temporal response lag so that the measured response is delayed with respect to the device (GPR system) position. | ||
| horizontal stretch | A term used to describe stretching the horizontal (position) axis of a cross-section image. If GPR data positioning is distorted, this is a means of regularizing the spatial position so that distance is a linear-axes on a GPR cross section image. Sometimes the process is referred to as rubber banding or rubber sheeting since the effect is to stretch or squeeze the spatial axis of the data is achieve uniform spatial presentation. | ||
| hyperbola | Characteristic inverted “U” GPR response from a point target. (Mathematical form of the position-travel time response from a point target). The apex of the hyperbola (top of the inverted U) represents the location of the GPR system’s closest approach to the object. | ||
| hyperbola velocity estimate | A point source GPR refection appears as a hyperbola in the cross-section image. One of the parameters controlling the shape of the hyperbola is the ground velocity. Hyperbolic fitting enables the ground velocity and target depth to be estimated. | ||
| hyperbolic fitting | Process of fitting a hyperbolic shape to a local GPR response in the space-time domain. The fitting process yields a velocity estimate for the material (media) above the target and a depth estimate of the target. | ||
| lateral resolution length | The minimum lateral separation between two objects required so a GPR clearly detects two side-by side responses. | ||
| Line Profiling or Common-offset profiling | is the term to describe collecting data along one or more GPR lines for immediate site assessment using cross-section images. A series of lines can be used to help define site conditions prior to a grid survey. Also see Common Offset Reflection (COR). | ||
| Line | is the term used to identify the location of a single GPR data set. A line is normally straight, and data are recorded from the start to the end of the line. | ||
| Lowpass Filter | removes frequencies above a cut-off frequency – useful for removing high frequency noise in GPR data. The filter can be a zero-phase or causal type filter. It can be applied in the frequency domain via Fourier methods or in the time domain by convolution. | ||
| magnetic permeability | u | A fundamental physical property that describes the magnetic polarizability of a material. Free space or vacuum has a permittivity of 12.57 x10-7 H/m. Most often the term is applied to the relative permeability where the material permeability is divided by the free space permittivity. Most natural materials have a relative permeability. For most materials relative permeability is in the range of 1 +/- .00001 in the radio frequency range. For this reason, permeability has no impact on GPR signals. | |
| Megahertz | MHz | A measure of frequency equal to 1 million repetitions per second. See frequency. | |
| microsecond | microsecond =10-6s = 1000ns; occasional unit of GPR time. | ||
| Migration | The process of collapsing the response of a point target back to the source point. Common term in reflection seismic and similar to synthetic aperture image reconstruction. Can be visualized by thinking of the signal on a hyperbolic response being summed and placed at the apex of the hyperbola. | ||
| multiplex: | the process of creating a single stream of data obtained from a multiplicity of receivers or detectors. (The sequencing is normally fixed- i.e. for four channels named 1, 2, 3, and 4, the sequence of the samples in this serial stream might be … 1a, 3a, 2a, 4a, 1b, 3b, 2b, 4b, 1c, 3c, 2c, 4c, where a, b, c refers to each cycle of selected channels…) | ||
| multi-polarization configuration (multi-polarization): | Describes a multi-channel GPR configuration where there is more than one polarization of the antenna elements. The terminology will take on two forms namely, one when single lines are being surveyed in which case the PR-BD, PL-BD, PR-EF, PL-EF, X-POL terms are used whereas if an area is being covered we will have the XX, XY, YX, YY terminology being used. Refer to the pulseEKKO manual for more details. | ||
| nanosecond | ns | ns | 10-9s (One Billionth of a second) |
| odometer calibration value | ticks/m | Odometers and distance measuring indicators (DMI) are based on encoders that generate a defined number of electrical signals (normally referred to as ticks) per revolution of the encoder. When attached to a wheel, the wheel diameter dictates the distance travelled per revolution. To calculate an accurate measure of distance travelled, an “odometer calibration” is required which is usually attained by measuring the number of ticks that are observed when the wheel traverses a known distance. Calibration is the result of this measurement process converted to a value for the number of measured ticks per unit distance such as ticks/m. | |
| penetration depth | The maximum depth for buried targets for which reflected signals can be detected. When a GPR pulse travels into the ground, it decreases in amplitude because of geometrical spreading of the energy and absorption of the energy by the medium. At some point the signal amplitude gets so small that it is no longer detectable. The depth that the signal amplitude falls below detectability defines the penetration depth or depth of exploration. | ||
| picosecond | ps | A picosecond is 10−12 seconds (one trillionth of a second). | |
| point stacking | Term used to describe stacking (averaging of repetitive observations) at a single time point. Often done when using a Digital Equivalent Time Sampling (DETS) receiver. Stacking is carried out sequentially for all the points in a GPR trace. | ||
| Points per Trace (N): | N | the number of sample points in a GPR trace. | |
| Power Cable Detector | PCD | A sensor that detects the alternating current in electrical cables using the magnetic field intensity produced. The sensor is normally attuned to detect the magnetic fields that oscillate at 50 or 60 Hz which are the standard oscillation rate for power lines carrying electric current. | |
| pulse repetition frequency | PRF | kHz, MHz | acronym for pulse repetition frequency. For a GPR system, it is the number of times the transmitter emits a pulse in a second. |
| pulse repetition period | PRP | ms, us | acronym for the pulse repetition period. For a GPR system, this is the time interval between transmitter firings and is equal to 1/PRF. |
| pulser voltage: | volts | the peak amplitude of the voltage pulse applied to a GPR transmitting antenna. Impulsive GPRs are characterized by this voltage. This is a simple alternative means of defining the energy available to be emitted. Energy is stored in a source power supply and released when the transmitter is triggered. The GPR signal at a distance is directly proportional to the peak voltage. | |
| radio wave | Electromagnetic fields that travel through a material as waves. Radio signals which are commonly in the frequency range of 1 MHz to 1,000 MHz and electromagnetic waves in this frequency range are generally referred to as radio waves. (Electromagnetic signals in the 10, 000 MHz range are similarly referred to as microwaves. Light waves are just higher frequency electromagnetic waves.) | ||
| range resolution length | The minimum radial distance separation between two objects required so a GPR clearly detects two vertical responses. | ||
| receiver | Rx | General term for electronics device used to detect electromagnetic field strength and translate the signals into electrical voltages or currents to be recorded or displayed. Modern receivers generally convert the signals into digital values (numbers) for recording and display. | |
| reflection coefficient | normally named “Fresnel reflection coefficient”. Quantifies GPR signal reflection amplitude from a flat interface between two materials. | ||
| reflectivity | measure of signal amplitude returned by a target. | ||
| relative permittivity | K | See dielectric permittivity. | |
| resolution | The minimum separation of two objects before their individual responses merge into a single response. | ||
| ringing | Impulsive GPR signals can give rise to reverberating responses that oscillate for a much longer time than the GPR pulse or wavelet. Such a response is referred to as a “ringing” response or “ringing” for short. | ||
| sample point | Signal amplitude measured at specific point in time. | ||
| sample time interval | the time between success sample points on a trace which is usually a constant fixed value and is selected to assure that the Nyquist sampling criteria are met. | ||
| signal amplitude | The value assigned to amplitude of the radio wave signal at a point in time. | ||
| Signal-to-noise ratio | The ratio of GPR signal amplitude to the average noise amplitude. A large ratio results in a larger penetration depth or the ability to detect weaker signals. | ||
| Slice | Describes the GPR data in a time or depth slice when the data is displayed as a computer-generated image. | ||
| Spatial Filter | Spatial filters act on GPR data in the spatial (or positional) direction. These filters use adjacent traces during the filtering procedure and alter the shape of the trace through various mathematical manipulations designed to enhance or eliminate certain responses. For example, Background Subtraction is a spatial filter that removes flat-lying responses in the GPR data. | ||
| Spreading & Exponential Compensation Gain | SEC | SEC gain is a composite of a linear time gain and an exponential time gain which attempts to compensate for the spherical spreading losses and the exponential ohmic dissipation of energy with depth in the GPR Line. | |
| stacking | term used to describe recording many repetitions of a signal and computing the average value. | ||
| stacks | The number of repeated measurements averaged to get a resulting measurement. | ||
| station interval | Spatial distance between observation points along a survey traverse line or mesh points on a grid. | ||
| step size | See station interval. | ||
| system performance | Q | Measure of system exploration depth indicated by the ratio of transmitter output power or voltage to receiver noise power or voltage. | |
| time gain | GPR signal amplitudes decrease rapidly in amplitude versus delay time after the transmit pulse is emitted. Time gain is the term applied to the operation of applying an amplification, which increases with time, to the signal, attempting to compensate for large differences in signal amplitude. This is a non-linear operation. See gain. | ||
| time sampling interval | delta-t or Δt) | ns or ps | The time interval between sample points on GPR trace; usually a constant interval. The interval is usually adjusted to match the GPR frequency of operation and often set automatically by the system based on GPR frequency. |
| Time Slice: | is the term to describe the data acquired between two times – top of time slice and bottom of time slice. Most often a grid survey has the maximum time subdivided into a number of time slices of equal thicknesses. | ||
| Time Window | ns | The maximum recording time selected for a GPR measurement. Normally set in the field during measurement but can be reduced when viewing processing data after acquisition. | |
| Topography Files | A topography file is a text file containing GPR line positions and the elevations at those positions. When a topography file is attached to a GPR line, elevations for every GPR position are interpolated saved into the elevation field of the GPR trace header. | ||
| trace | Sequence of sample points from a single GPR channel that indicate the time variation of signal amplitude. | ||
| Trace Plot | Process of plotting traces side-by-side to create an apparent cross section of the ground. Trace number, which is normally equivalent to horizontal position, increases in the horizontal direction while data points on the trace are plotted in the vertical direction representing increasing signal delay time or depth. | ||
| Trace Repetition Rate | traces/second | the number of GPR traces that can be collected in a given time interval normally determined as 1/ (PRP x Points per trace x stacks) + delay time)). | |
| Trace Stacking | term used to describe stacking (recording and averaging) of complete traces. | ||
| Trace Time Interval: | Time between acquisition of sequential traces in free run data acquisition mode. | ||
| transducer | Name used where GPR antenna, electronics, and shield are combined into one physical unit. | ||
| transmitter | Tx | General term used for electronics devices used to create propagating electromagnetic fields | |
| Transmitter Output Voltage: | Volts (V) | the peak output amplitude of the transmitter electronics that is fed to the antenna. | |
| Two-dimensional (2D) array: | GPR array elements can be distributed over a flat surface to form a two-dimensional array of elements. (Note in some rare cases arrays may also be 3D) | ||
| Universal Transverse Mercator (UTM) | UTM | UTM is a geographic coordinate system that uses a 2-dimensional Cartesian coordinate system to give locations on the surface of the Earth. It is a horizontal position representation, i.e. it is used to identify locations on the Earth independently of vertical position but differs from the traditional method of latitude and longitude in several respects. | |
| UTM Letter | Each UTM zone is segmented into 20 latitude bands. Each latitude band is 8 degrees high and is lettered starting from “C” at 80°S, increasing up the English alphabet until “X”, omitting the letters “I” and “O” (because of their similarity to the numerals one and zero). The last latitude band, “X”, is extended an extra 4 degrees, so it ends at 84°N latitude, thus covering the northernmost land on Earth. Latitude bands “A” and “B” do exist, as do bands “Y” and “Z”. They cover the western and eastern sides of the Antarctic and Arctic regions respectively. | ||
| UTM Zone | The UTM system divides the Earth between 80°S and 84°N latitude into 60 zones, each 6° of longitude in width. | ||
| UTM Zone Number | Zone 1 covers longitude 180° to 174° W; zone numbering increases eastward to zone 60 that covers longitude 174 to 180 East. | ||
| velocity | v | m/ns or m/us | is the term used to characterize the speed at which GPR signals travel in a media. Velocity is a critical parameter when creating depth slice images and estimating depths of targets since velocity is used to convert travel-time to depth. |
| Vertical Filter | Applies a running average filter vertically (down-the-trace) to a GPR trace plot. The signal is averaged by replacing the data value at a given point by the average data value over a window centered about that point. Its primary purpose is to reduce random or high frequency noise by acting as a low pass temporal filter. | ||
| wavelet or EM pulse | Impulsive GPRs emit an oscillatory electromagnetic pulse which is short in time and space and is often referred to as a wavelet. | ||
| X Line Spacing: | the term used to refer to the spacing between X lines when a grid is covered by equispaced X lines. | ||
| X Line: | A line oriented in the X direction. (i.e. Y = constant while X position varies). This is a GPRLine convention when collecting GPR data in a grid. | ||
| X Slice: | time or depth slice image created from X lines in a grid. | ||
| XY Axes: | X and Y are the names given to the two orthogonal directions of a grid. When positioned at the specific corner of the grid which is selected to be the origin of the coordinate system and facing diagonally across the grid, the positive X direction runs to the right along the edge of the grid and the positive Y direction runs straight ahead. | ||
| XY Slice: | time or depth slice image created from combining both X and Y lines in a grid. | ||
| Y Line Spacing: | the term used to refer to the spacing between Y lines when a grid is covered by equispaced Y lines. | ||
| Y Line: | A line oriented in the Y direction. (i.e. X = constant while Y position varies). This is a GPRLine convention when collecting GPR data in a grid. | ||
| Y Slice: | time or depth slice image created from Y lines in a grid. | ||
| zero time | The time of first emission of signal by the transmitter. This time should be equated to the first break time unless the transmitter receiver separation is zero. | ||
| zone of influence | The size of an area on a reflecting feature that can be uniquely resolved. (See Fresnel zone definition and lateral resolution length). |