An interactive tool has been developed for visualizing and creating scaled battlefield based scenarios for use in a simulation testbed to develop and test distributed data fusion and ad-hoc networking algorithms. This paper discuses the design requirements and implementation issues for developing such a tool. Two main design goals were to enable design of complex scenarios in an intuitive and easy fashion, and provide a complete set of decision support utilities. The tool, called SceneGen, supports 3D visualization for creating scenarios and overcoming challenges including geospatial (GIS and Terrain) data management, entity information management and waypoint/path specification. The scenario generator includes a number of sensor and target models and provides database support to manage different fusion and network algorithms. This tool was implemented and tested successfully with several sample scenarios.