US Radar Inc. website has lots of great information about how GPR works.
GPR simulation software.
GprMax is a free Ground Penetrating Radar (GPR) simulator.
GPRSim.net is a basic GPR time domain simulation tool.
Data processing and visualization software.
The Visualization Toolkit (VTK) is an open-source, freely available software system
for 3D computer graphics, modeling, image processing, volume rendering, scientific visualization, and information visualization.
ParaView is an open-source, multi-platform data analysis and visualization application.