Thank you for you more scientific analysis, tex
.
I checked again in a training mission. A ship is sitting at 1000 yards, another one at 2000. The range indicator of the active sonar device both time shows the 1000 and 2000 yards respectively.
I agree that the pong needs twice the sound travelling time to the target but the sonar indicator is set to include this already. If it shows 4000 yards it means that the ship is 4000 yards away but the sound had to travel of course a distance of 8000 yards.
Weird thing though, that the stadimeter was absolutely sure about the distance of 2000 and 1000 yards to the ships while the active sonar was absolutely sure that those were 1800 and 900 yards away. (Probably the stadimeter's fault because RFB fiddled with the mast heights but who knows...).