Machinbird, I think that the past Pitot freezing events (interim report #2) tend to show that the false stall alarm rate is far higher than the false overspeed alarm rate ? beyond AndiKunzi's mechanism, maybe another one leading to (peaks of) overestimated AS was put forward some time ago (I don't remember who suggested this): when the heater eventually takes over a weakening ice crystals event, the accumulated ice in the Pitot tubes could melt then approach boiling temp creating bubbles/overpressure peaks on the analog to digital measurement device ?
HN39, if the ranges (or the different times of arrival of the pings) cannot be measured (only the directions of arrival), it relies on several triangulations from several different positions of the sub ? If a doppler (relative speed of the sub versus target) could be measured, it would provide some other angular clues.
Jeff