Geometry is geometry but he used two angles from it and applied to coordinates. Our Ships give a planet a 0,0. Which is on the equator somewhere. Just because we picked a point on the planet as 0,0 doesn't mean another race would pick the same point. They can pick any other point on a planet's equator as an origin then give us coordinates. We go to those coordinates as displayed on our ships and nothing will be there. Without knowing both races use the same point of origin, we can't use coordinates.
For this reason I think the closest we'll get is a planet, not coordinates. Perhaps a planet in each system, I think a "daisy-chain" pattern is more likely. We find one more ruin, that leads us to another, and so on.