The nav can read the doppler drift out over the intercomm at, say, 200 feet, and the pilot can set it manually. That way, the nav can check that the doppler's locked on at the time. If it isn't, he still has the ATC surface wind and his CRP5 (or the USAF equivalent).
These days, it's probably available off the INS anyway, because the B52 has had several mid-life updates of the nav and weapons systems. And INS doesn't unlock.