Abstract: A method for sonic analyzation on-line and in real time or off-line in post processing of a topographic representation of a seafloor to provide the latitude and longitude of an object producing a corresponding anomaly appearance identified in a topographic respresentation generated from a side scan sonar tow fish includes in the on-line, real time analyzation the steps of sequentially touching the tip of a sonic digitizer stylus to a point on the line representation of the seafloor laterally opposite the appearance of the anomaly; to the leading edge and the trailing edge of the anomaly and to the tip of an acoustic shadow of the anomaly appearance; and, if length is desired, to the top and bottom edges of the anomaly appearance. A computer includes a set of instructions to calculate the desired information and is coupled to a host computer associated with a vessel which tows the sonar tow fish along a course covering an area of interest of the seafloor.