The pole barn, if it has a metal roof, can become a fairly effective lightning shielding “carapace” that is less likely to allow a strike to attach itself to your camper if you can electrically join the roof sheets together and ground it all with enough significantly sized downlead conductors to rods that are long enough to be effective (reaching into “not powder dry” subsoil).
Getting everything up there bonded together electrically and paying for the lengthy amounts of large conductors and ground rods required won’t be cheap, though. And Exothermic Welding of connections, a sort of “Bless this Holy Hand Grenade” joining technique that surprises customers who never saw it done previously (Monty Python Holy Grail Reference!) is preferable for lasting, effective connections in some of what needs done in grounding work vs. relying on bolted or clamped connections.
Of course once you achieve a well earthed bonded roof with uniformly distributed down lead conductors, the random chance of getting struck by being just one of many things in your neighborhood area that the lightning could attach to, may change to where your roof may be electrically "more available” as a target for lightning to attach to.
In my misspent youth, lightning gave me an up close understanding of being electrically “more available” in 1973 on the Intracoastal waterway during a serious afternoon thunderstorm. On a 14 foot catamaran, tossed in whitecaps, soaked to the skin, me and another pal, Roger, from our high school, heard an intense frying sound get going from the top of the sailboat’s mast; us out in the channel, plunging mightily through the wild chop at speed, from just a half-raised jib that we still had up by itself. We had no motor and were unable to get off the water in time. (Saw it coming.. wind direction not initially against us, stupidity of our youthfulness…)
The frying noise began to reduce after a bit as the broad, black-fronted storm went onward over us. We got to shore and thanked God to not have been struck out there. Roger went on to become an Air Force Pilot, but refused to boat with me ever again.. If it had been night, we probably would have seen the ionization trail that was going up into the sky from our mast. A golfer told me years later that he would not have been afraid to boat with me like that, but would insist on bringing along a nine iron. I asked him why. He claimed that not even God could hit a nine iron… I am not convinced of that!
