Abstract: An automatic clutter detecting and mapping system in which the area being mapped is broken up into clutter mapping quantum areas with corresponding storage cells including reject codes for automatically rejecting clutter returns which may occur in intermittent or fading clutter occurring a small percentage of the time for example. For each clutter mapping cell a clutter count and a reject code are stored in a main memory and in a first mode which is searching for clutter the clutter count is incremented by eight in response to an input targert but is not decremented in the absence of a received target from that clutter mapping area. In any clutter mapping cell when the clutter count reaches a threshold within a selected number of scan periods, the reject code is set to the amplitude corresponding to the maximum amplitude target report received in that cell and provided by a temporary memory.