Why better navigation would not free sailing fleets from geography

How much would GPS help a French Age of Sail fleet?

It would improve navigation, but it could not remove the constraints of wind, tide, current, and the routes fleets had to use.

A French fleet with GPS would know its position more accurately, but it could not manoeuvre freely. Wind, tide, and current still restricted the routes sailing fleets could use and concentrated operations around predictable approaches. The Western Squadron's position off Brest and the Channel mattered because French fleets had to pass through its operating area. A long detour would cost time and still leave the fleet open to interception. Accurate positioning could also encourage misplaced confidence if the available charts were poor.