"due" instead of "to"?

Question

"Take your orni and fly due south-west."

I heard this quote in a dialogue from the game "Dune" and I am wondering if the usage of "due" is applicable in this case.

Answer 1

In your example sentence due is used as an adverb. According to The Free Dictionary, definition #1, as adverb, it means straight, directly.

1. Straight; directly: Go due west.

Answer 2

"Due" in this case means "exactly". That is "due southwest" means to travel at 225 degrees (if north is 0).