[en] A prototype of a real-time radiation mapping system, Ranger, was developed to respond to an accident involving the release of plutonium for the Department of Energy's Accident Response Group. In 1987 Ranger demonstrated that it can provide an efficient method of monitoring large areas of land for radioactive contamination. With the experience gained from the operation of the prototype, the external computer and software are being upgraded in order to obtain a fully operational system. The new system uses the prototype's commercially available line-of-sight microwave system for determining position and the same radiation detection instruments. The data obtained from the radiation detection instrument(s) are linked back to the external computer along with the relative position of the measurement through the ranging system. The data are displayed on a gridded map as colored circles and permanently stored in real-time. The different colors represent different contamination levels. Contours can be drawn using the permanently stored data. 4 figs