Surely the Tristar predated GPS by some years.
you are correct of course. It was INS groundspeed. For those unfamiliar with how this works it’s easy. Say VRef +5 =140. Surface wind headwind 30 kts. Fly approach at 110 g/s.
Target threshold speed less headwind. All the way down. Guarantees excellent speed control and avoids wind gradient shear effects.