Road poneglyphs are a star map and Nami will learn star navigation from the giants.

Giants can navigate sea by stars and laughtale cannot be found by compass or log pose. Idk why LT cannit be found by lig pose and i believe there is a lot of theory potential there but that is nit what this theory is about. Since the road poneglyphs need to be read, they are probably a verbal description. As for why do that as opposed to just drawing a map, it is so that only the right person can read it. Giants will teach nami offscreen at the end of elbaph. I originally had this as a 1192 prediction but took it down and moved it here.