[TowerTalk] Locating Buried Feedline

[Barkey, Patrick M.]

I'm getting ready to trench in a cable line to a new tower, and before
I do, I'd like to mark where the existing cables are buried,
particularly
near the shack where they all come together.
 
Any ideas what the most reliable/cheapest way to do this is?
Obviously, I will be digging by hand when I get in the "crossfire"
of existing cables, but I know that you can do a lot of damage with
an errant spade in just one swing.
 
Thanks.
 
  - Pat
    N9RV