This proposal introduces an innovative sensor to advance ground collision avoidance for UAS platforms by providing real-time height maps for hazard anomaly detection. This sensor will also provide enhanced vision to overcome reduced visibility in fog, drizzle and light rain and the detection of hazards/obstacles on runways for landing and takeoff applications. Specifically, this effort will build upon a developing synthetic vision system for landing piloted aircraft to: 1) customize the design and feasibility for targeted unpiloted autonomous systems (UAS), and 2) incorporate interferometry for terrain mapping and hazard detection. Dubbed "PathIn", the proposed sensor is comprised of a Ka-band digitally beamformed (DBF) radar interferometer that will provide a real-time data interface for ground-collision avoidance systems. The proposed effort is aligned with the effort to integrate UAS into the National Airspace (NAS). The Phase II will realize a prototype of the PathIn sensor, leveraging our extensive radar, interferometry and DBF experience and key technology capabilities. In particular a FPGA-based digital receiver system will be extended for real-time beamforming and interferometry. At the end of the Phase II, a technology readiness level of 5 will be achieved.