Meaning of the four circles on ships

[greybeard_52]

When I click with mouse on warships sporting on F5 map, four circles appear (indeed the smallest one misses a slice toward the stern). Could you please mention their respective meaning?

[trickytrevor46]

The 1st half circle represents the sonar dead zone of around 400 to 500 Mtrs in front of ship due too the coning of the sonar, which is the best time too speed up underwater and try and turn from his track. The uncompleted circle at the rear is its sonar dead zone directly behind the ship because of propeller noise from same. the further circle is the viewing range from same ship hope this helps..Happy Hunting ....SNAFU

[greybeard_52]

Thank you!