Wow. This developement caught me totally off-guard. Last time I checked, it was not possible for some reason to make the sub-icon disappear on the nav map. Now I've read about it twice, the first time thinking I must have misunderstood when someone mentioned it.
Thanks a lot dertien for providing the invisible sub icon here, now I can't see it I can see it's true lol. I used to print out the in-game patrol charts back in SHI and do manual navigation, it was great fun! Printing out was easy though since the PTO in SHI was divided up in several single maps and some people over at Subsowespac, namely George Southrey, already did plenty of the required research.
Check this site for nostalgia:
http://www.subsowespac.org/tactics/navigation.shtml
Printing out proper maps for SHIII would mean a lot more hassle I think, but now with the sub icon gone we have all the tools neccessary.
BTW, I'm still on Vanilla SHIII and still unsure about installing GWX or NYGM. Do you know whether they both feature more readable gauges (mainly compass), which would be mandatory for manual navigation, or would I have to d/l those seperately anyway?