Charla:

What else could depth sounding be used for? Nothing, just used for finding the depth at a given point on the sea bottom.

That old WWII fleet boat I rode (USS PIPER (SS-409) had a BQR-4 passive array
installed around its bow. It worked out great tracking Soviet "vessels"in the Faroe Islands "choke-point" during the cold war, in 1957-58.

When USS NAUTILUS (SSN-571) attempted her Arctic transit, she used a WWII
QLA forward-looking sonar system that was used on fleet boats in the Perouse Straight near Japan, for detecting mines. There was no other forward-searching sonar available. It was canted up at 8 degrees in order to detect overhead ice.

The "scrambled ping" was still a pin-point sounding, that could not be detected by others. The sea-bottom charts were presented similar to a topographic map, showing mounts, valleys and flat plains of the seabed. The charts were used just like a contour road map. They were very long charts and stored in a rolled-up manner. They were spread out atop lockers in the starboard upper level of the missile compartment for viewing. Charles Lindberg's son partipated in this effort in 1958 conducted by the Coast and Geodetic Survey group, now known as NOAA. This is all my 78-year old memory circuit can produce, sorry about that. Most of my bublehead boat-riders do not care to talk abut this stuff; you know "SILENT SERVICE"..........But this is all history!

I don't know what type sonar the later U-boats used, but they had no idea what this
"secure" FATHOMETER was all about. The U.S. Navy did experiment with the
sound equipment on U-2315 and U-3008, and I'm sure it advanced our capabilities.
"To the victor goes the spoils of war" The present spherical-array bow sonar installation on fast attack boats is remarkable. I cannot say much more than that at this time.

While riding a boomer on a deterrent patrol, our submerged speed was usually "all ahead standard" or 15 knots at 450 feet. There was no surface speed on a patrol.

The navigator's job on a NUKE boat is somewhat different than on a U-boat. He can
use SINS (ship's inertial navigation system), the transit satellite antenna, LORAN, GPS and if need be, dead-reckoning.........times have changed, and this is only the beginning!

Due to 5 years of constant research of arctic under-ice navigation, ending in 1999,
a "blueprint" of seasonal ice movements by scientists, has provided valuable data
for under-ice transits in the North polar regions. Up-looking sonar systems can locate "polyanas" (ice ponds) in the ice, where a submarine can surface to communicate or whatever. The depth soundings were recorded for posterity. The
ice-cap is continually moving in a circular mode.

Cheers,

ROBERT M.