GPR用語集
| 用語 | 一般的なシンボル | 典型的な単位 | 説明 |
|---|---|---|---|
| 3 dB帯域幅 | MHz または GHz | GPR信号の振幅が（ピーク振幅 /√2）と等しい値を上回る周波数範囲。 | |
| 3Dビュー | 表面積をカバーするデータを表示する際に使われる用語で、第三の次元は時間または深度または時間である。データはボクセル（小さな立方体状の体積）に分けられ、データ値は体積レンダリングツールを使って表示され、断面スライスや3D体積の可変透過率がレンダリングされる。 | ||
| 6 dB帯域幅 | MHz または GHz | GPR信号の振幅が（ピーク振幅 /2）と等しい値を上回る周波数範囲。 | |
| 取得モード | GPRトレース取得を開始する方法を表す用語。一般的な方法は以下の通りです: 距離 – トレース収集は空間的な位置（通常は等間隔）で行い、位置はオドメーターやその他の距離測定装置で決定されます。フリーロン – トレースはシステムが許す限り、順次収集されます。時間 – トレース収集は、トレース間または前のトレース収集終了後の遅延時間を定義した時間間隔で制御されます。外部トリガー – トレース収集は、手動ボタン押下や電子入力信号などの外部トリガーによって制御されます。 | ||
| 集計 | 分級された破片で混合に使用される硬く、無害な鉱物材料。砂、砂利、砕石、スラグなどが含まれます。コンクリートやアスファルトの作成にしばしば使用される材料です。 | ||
| 空気波 | GPRシステムは、送信機から全方向に進む電波エネルギーを放射し、受信機で全方向から受信されます。GPRは地下の信号を検出するために使用されます。地上の物体から反射した、地面上を伝わるGPR信号は、空気波と呼ばれる望ましくない整合性のある雑音信号を引き起こします。 | ||
| アンテナ | 電気信号を伝播する電磁波に変換するための装置。GPRでは通常、送信アンテナと受信アンテナがあります。送信または受信の電子機器と組み合わせると、トランスデューサ（変換器）という用語が使用されます。（トランスデューサ参照） | ||
| アンテナの分離 | GPRは通常、送信と受信に別々のアンテナを使用します。アンテナの物理的中心間の直線距離は、アンテナの分離と呼ばれます。 | ||
| アレイ | 複数の送信および受信アンテナを含む高度なGPRシステムで使用される用語。各要素の空間的な位置が定義された空間領域に配置されます。 | ||
| 減衰 | α | ネパーまたは dB/m | メディア内でエネルギーが散逸することによって、伝播する信号の振幅が減少する現象を指します。GPRでは、減衰は通常、メディアの電気伝導率と関連しています。 |
| 自動利得制御 | AGC | 信号強度に反比例するゲインを適用することで、すべてのGPR信号の振幅を均等にするゲイン関数。これにより、反射イベントの連続性を定義するのに最も役立ちます。 | |
| 平均周波数スペクトル | AFS | GPRデータファイルまたはセクション内のトレースの振幅スペクトルを計算し、平均化するプロセスを説明するために使用される用語。プロットは信号の周波数内容を示し、バンドパスフィルターを適用するなど、周波数フィルタリングのパラメーターを決定するのに役立ちます。 | |
| 平均トレース振幅 | ATA | GPRライン全体の平均直流信号振幅を表示するプロット。このプロットは、GPR信号振幅がどれだけ速く減衰するかを表示する強力な方法であり、周囲のノイズレベルを評価して、GPR信号の最大深度を示す手がかりを提供します。 | |
| 背景平均差引 | BAS | GPRデータセット内のすべてのトレースの平均を計算し、この平均トレースをデータセット内のすべてのトレースから引くプロセス。主に、GPRデータの質が悪い場合に使用され、GPR画像に現れる定常的なバンドとして現れるシステムノイズを抑制します。このプロセスは、ポイントターゲットからのハイパボラなどの空間的に変動する弱いイベントを視覚的に際立たせるために使用されます。また、時間ゼロで表示される直接空気波および直接地面波（送信パルス）を除去するためにも使用されます。 | |
| 背景差引 | BSUB | このプロセスは背景平均差引と似ていますが、個別に処理されたトレースを中心とした局所的なトレースセットに対して実行され、引くべき平均背景トレースを取得します。このプロセスは、ポイントターゲットからのハイパボラのような局所的なイベントを強調し、水平方向またはゆっくりと変化するイベントを抑制します。局所的な平坦なイベントを除去するのに非常に役立ちます。また、時間ゼロで表示される直接空気波および直接地面波（送信パルス）を抑制するためにも使用されます。 | |
| バンドパスフィルター | 特定の周波数範囲をGPRデータに保持し、それ以外の周波数を抑制するプロセス。GPRは超広帯域録音装置であり、GPR送信機によって生成されないノイズ信号が含まれることがあります。保持および抑制する周波数の選定を慎重に行うことで、GPR画像の解釈可能性を高めることができます。バンドパスフィルタリングは主にフーリエ解析とスペクトル加重を使用して行われますが、適切な時間フィルタインパルス応答によるGPR信号の時間畳み込みによっても達成できます。 | ||
| 帯域幅 | 特定の機器が信号の振幅または出力が指定された値を超える範囲で信号を送信または検出する周波数の範囲。 | ||
| 中心周波数 | 超広帯域装置に特に定義された用語。信号振幅（例えば3dB帯域幅）に基づいた上限および下限のカットオフが定義されます。上限および下限のカットオフ周波数の平均が中心周波数として定義されます。多くの場合、中心周波数はGPRシステムのスペクトル振幅がピークになる周波数に非常に近いため、ピーク周波数と中心周波数はしばしば同義で使われますが、これは厳密には正しくありません。 | ||
| チャネル | 単一のTX-RXアンテナペアによって作成されたGPR信号を説明するための用語。これらには、周波数、分離、方向などの固定されたパラメーターがあります。（また、配列要素の定義も参照してください。） | ||
| カラーバー | 色の範囲を表示し、通常は特定の色が示すデータ値の範囲（通常はGPR信号振幅）を表示する色のバー。 | ||
| カラーパレット | データ値を色にマッピングするプロセスを指す用語。時にはカラーテーブルとも呼ばれます。最も一般的には、GPRで横断面、深度または時間スライス画像、および3D画像の作成時に、データ属性（例えば振幅）の値を色に割り当てるために使用されます。 | ||
| 共通中点 | CMP | 共通中点（CMP）は、送信機と受信機のアンテナ位置が変動しますが、移動方法が中点を一定に保つように行われるGPR調査タイプです。 | |
| 共通オフセット反射構成 | COR | データが固定されたアンテナジオメトリで収集され、位置から位置へと移動する際に使用される用語。通常、送信機と受信機のアンテナの向きや分離も固定されています。ラインプロファイリングも参照。 | |
| 同時受信機操作 | 複数の受信機が同時にデータサンプルを取得している際に使用される用語。データ取得は同期され、すべての受信機が単一の送信パルス放出後に同時にデータを取得します。各受信機のタイミング精度は、成功したデータ取得を達成するために10ピコ秒単位である必要があります。これにより、歴史的な多重受信機操作と比較して、GPRデータ取得が大幅に高速化されます。 | ||
| 導電率 | σ | ミリシーメンス/メートルまたはmS/mまたはミリモス/メートル（歴史的な単位） | 物質が電流を導く能力。各方位の物質において、これは抵抗率の逆数です。特定の導電率とも呼ばれます。 |
| 横断面 | 隣接する空間測定位置からのいくつかのトレースを並べて表示することによって得られる画像。 | ||
| デシベル | dB | 比率を表現するために使用される単位で、比率の20 log10に相当します。比率が10の場合は20デシベルに相当します。 | |
| 深度変動ゲイン | トレースが掛け算される深度によって変化する乗数的な要因を指す用語。その目的は深度に対する相対的な信号振幅を変更することです。時間変動ゲインも参照。 | ||
| 深度またはセクション画像 | GPRデータトレースを横に並べて地面の画像を作成する際に使用される用語で、縦軸は深度であり、通常は信号伝播時間を深度に変換することによって得られます。通常、この用語は深度セクションまたはセクションと短縮されます。 | ||
| 深度スライス（画像） | データの体積を通してスライスをレンダリングして色や等高線表示を作成することによって得られる画像を示すための用語。通常、コンピュータープロセスによって生成されます。この用語は通常「深度スライス」と短縮されます。 | ||
| デワウ | GPRデータから非常に低周波成分を除去するプロセス。この低周波データ成分は誘導現象や計器の動的範囲制限に関連している場合があります。GPRトレースのベースラインは、上下にゆっくりと揺れ動きます。GPRの初期には、この現象は「ワウ」と呼ばれていました。この効果の除去は「デワウ」と呼ばれるようになりました。 | ||
| 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). |