Pioneers in side scan sonar: Julius Hageman and the shadowgraph

The concept of the side scan sonar was developed during the early 1950s at the U.S. Navy Mine Defense Laboratory, Panama City Florida—now known as the Naval Surface Warfare Center Panama City Division. In technical reports and laboratory notebooks, Dr. Julius Hageman, a German scientist who relocated to the Laboratory after World War II and worked there until his death in 1964, outlined the proposed “short-range high-definition mine location sonar” that would eventually become the C-MK-1 mine classification sonar system, more commonly known as “Shadowgraph.” Hageman’s patent for the concept (US Patent 4,197,591) was first disclosed in 1958, but remained classified until finally issued in 1980. The Shadowgraph was contracted by the U.S. Navy in 1957 and towed primarily from Oceangoing Mine Sweepers. It was operated as an undersea search and survey tool for more than 25 years before decommissioning in 1991. The Shadowgraph was a 1.5 MHz dual-sided side scan sonar, with range of 100 feet, and imaging resolution of approximately 3 in. square at a range of 75 feet. During its service life, it located numerous lost objects and aircraft on the sea floor and to this day has influenced the development of commercial and military sonars.