Boeing-SVS (BSVS) has been developing a Passive Obstacle Detection System (PODS) under a Small Business Innovative Research (SBIR) contract with NAVAIR. This SBIR will provide image-processing algorithms for the detection of sub-pixel curvilinear features (i.e., power lines, poles, suspension cables, etc). These algorithms will be implemented in the SBIR to run on custom processor boards in real time. As part of the PODS development, BSVS has conducted a study to examine the feasibility of incorporating a passive ranging solution with the obstacle-detection algorithms. This passive ranging capability will not only provide discrimination between power lines and other naturally occurring linear features, but will also provide ranging information for other features in the image. Controlled Flight Into Terrain (CFIT) is a leading cause of both military and civil/commercial rotorcraft accidents. Ranging to other features could be invaluable in the detection of other obstacles within the flight path and therefore the prevention of CFIT accidents. The purpose of this paper is to review the PODS system (presented earlier) and discuss several methods for passive ranging and the performance expected from each of the methods.