IIRC Snoopy had a Ferranti INS in the van in the cargo hold that the Met Office boffins would use to get accurate wind data after post flight number crunching. Some time in the early 1990s this was replaced with a Honeywell laser ring gyro INS, and the nav had a feed. Soon after this was joined by a NAVSTAR xr(?) 5 GPS. Again mainly for scientific use, the nav was able to enter way points and use it for basic navigation. Unfortunately I have had a look through the old albums and I don't have a photo of the nav station.