Key Words: Ground Penetrating Radar, Clandestine Burials, Geophysical Applications in Anthropology, Historic Cemeteries introduction and purpose
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| Operation of GPR GPR units today often consist of just a few components that are capable of being operated by a single user The antenna, the control unit, and the display, all powered by a battery. Often, these components can be loaded onto a cart or backpack for mobility. Many antennas used in GPR research today operate in bistatic mode two antennas are operated simultaneously with one acting as a transmitter and the other as a receiver. Another version of antenna type, known as monostatic, operates as both the transmitter and receiver after a pulse of radar energy the antenna automatically switches to act as a receiver. The display allows for real-time visualization, setting adjustment, and data storage. Survey wheels may also be attached to GPR units in a cart and can beset to collect location data to be integrated with GIS software (Conyers, 2004; Wardlaw, 2009; Gontz et al., 2011). GPR works by transmitting an electromagnetic pulse from the surface antenna into the ground which then propagates as a waveform. This wave will encounter variability in the electrical and magnetic subsurface matrix and so the physical and chemical properties of this matrix determine the speed at which the propagated wave is registered by the receiver as it returns to the surface. This two-way travel time is recorded in nanoseconds (ns), or one billionth of a second. Some of this energy will not return to the receiver due to certain chemical or physical properties in the subsurface. This is known as signal attenuation (Conyers, 2004; Conyers, 2012). The GPR unit will continue to emit radar energy and collect data as it is moved along a transect. This data will be displayed on the screen in real time depicting anomalies as they are encountered. These anomalies often appear as hyperbolas due to their detection by the receiver upon approach, while immediately over them, and upon moving beyond them (Figure 1). These D representations of a single transect are referred to as reflection profiles (Tischler, 2003; Schultz, 2003; Conyers, 2004). Download 0.69 Mb. Share with your friends:
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