IRL Navigation German Subs

[YellowFin]

Does anyone have any reliable information on the routes used by German submarines when they left port or returned? I'm interested particularly in the ones for the Bay of Biscay.

I have a few names but no charts or anything more concrete.

Names I gathered:

Point L2

Routes:
Tannennadel
Cedernland
Rosa
Rosabella (presumably south-bound from La Pallice) (I originally wrote Rosalinda, but I believe I confused the two names, no route Rosalinda mentioned) Burggraf
Lila (presumably in the English Channel)


From a KTB I read a while ago I believe later in the war there was a Route basically along the Iberian coast (don't remember the name) to avoid allied air activity as much as possible.

[ThePrody]

https://uboat.net/maps/piening-route.htm

[YellowFin]

Thanks, that's just one route though, and late war. Do we know anything about early and mid war routing?

[stork100]

One resource you might check if you need to is the BDU KTBs:

http://www.uboatarchive.net/BDUKTB.htm

A lot of the U-Boats grid positions are plotted on a daily basis, and you might be able to notice some patterns for the ones departing and returning. Not so much detail for the early war though. Best of luck.

[YellowFin]

Thank you, that's a great resource. I wasn't aware of the order collection. If anyone has more charts, please let me know.