Dotted lines around enemy vessels

[frogdog]

As I crank down on magnification on enemy DD in (say) Scrapa Flow, I get concentric dotted lines. Are these visual range distances...or what?

[_alphaBeta_]

Usually goes like this starting with the largest ring:

1. Visual range
2. Hydrophone range
3. Radar range (if applicable)
4. ASDIC (if applicable)

[frogdog]

Thanks. As a follow up (as they say at White House news conferences) do the rings reflect existing weather/light conditions or are they general regardless?