For ultrasonic or other mapping systems which use PPI scan, it is desirable to convert the data to a raster scan format for, say, T.V. display. This may be achieved by conversion in a frame store. It is here proposed to time the PPI scan so that points interrogated by the effective receiving beam lie also on line of a cartesian matrix in the mapped region which correspond to the raster lines of the display thus the conversion is directly achieved.




