Introduction and History Electromagnetic Wave Propagation
Velocity Wavelength Attenuation Dispersion
Rocks, Soils and Fluids: Electrical Properties Magnetic Properties
Environmental Influences Heterogeneity, Anisotropy and Scale Radar Equation
Scattering Polarization Fresnel Reflection Snell Angle Stokes-Mueller Matrices Poincare Sphere
Antennas Coupling Near / Far Fields Waveguides Multipathing Resonance
Survey Design Contrast Geometry Resolution Depth of Investigation Orientation
Interferences
![[Under Construction]](images/undercon.gif){kind=small}
Clutter
Metal
Side Scatter
Overhead Wires
Radiofrequency Noise
GPR Interference
The following is an illustration of one portion of the problem. A GSSI 500 MHz center frequency (in air) short pulse antenna is setup in a 6 m by 6 m by 3 m high underground room without walls in the interior of a large building. This is done to reduce the signal levels from the cell repeaters to an analog cell phone to investigate the interference both ways between the cell phone and the radar system. With the radar off, the cell phone indicates a signal strength in the room about 1/6 of that outside the building, and has no trouble obtaining service. With the radar on and the antenna properly coupled to the linoleum tile covered concrete floor, the cell phone can not acquire service within about 1 m of the radar antenna, but once having acquired service outside that range, has no trouble keeping it right up to the cell phone touching the antenna. There is no noticable change in the quality of the conversation up to contact. Note that the cell phone is operating at a frequency near 900 MHz and the radar antenna coupled to the concrete has a -3dB bandwidth of roughly 300 to 700 MHz. With the radar operating and the antenna stationary, the data in the figure below are obtained. On the left the cell phone is on, obtaining service, but not being used (in standby). On the right, the cell phone is turned off. In the middle, the cell phone is being used to communicate a voice conversation. The data at the position of the horizontal line across the bottom of the image are plotted across the top of the figure, clearly showing the change in noise amplitude levels with cell phone operation. Under the conditions on the right, the radar can map the thickness of the concrete, see the rebar in the concrete, and see the sewer pipe beneath the floor. On the left, the radiofrequency noise masks the sewer pipe so it cannot be found. In the middle, the active cell phone conversation makes rebar detection marginal and concrete thickness determination is not possible.
Data Acquisition Data Processing Modeling Interpretation Uncertainty
Applications: Noninvasive Surface Borehole Airborne Satellite and Space