Evaluation of Environmental Effects on GPS Navigation Systems

In this paper the development of a foam column scattering code is proposed, suitable for indoor and outdoor simulations, and accounting for interactions between support columns, ground and target. To specify the geometry, the code will use a graphical interface with CAD modeling of the columns, target, and ground. This CAD input removes the user from the inconveniences associated wiuth geometry inputs, which for complicated geometries are impossible to type in manually. A library of airframe CAD files has already been developed at Wright Labs and will be used by this code. To solve for the scattering, a hybrid computation is proposed. At low frequencies the column can be examined macroscopically by assuming it to be made of a homogeneous material, while at high frequencies it is modeled as a radom collection of individial scatterers. According to foam manufacturers, these scatterers take the shape of regular polyhedrons. By analyzing the scattering from individial scatterers, the entire collection can be statistically summed. Once the electromagnetic solution is obtained, it can be visualized with ray tracing, SAR imaging, time domain, and frequency domain information desplayed on target overlays. Also, measurements will be made for comparison, at both indoor and outdoor facilities.