Big Picture Science – Seth’s Wine Cellar: Anne Curtis

Hi There.

I enjoyed Anne Curtis and her explanation precision timekeeping and GPS systems.

Question: What reference point(s) on the ground does the GPS use to determine which street/highway/interstate that I am on. For example, I frequently pass under an overpass or drive parallel to an interstate. Sometimes my GPS will recalculate and tell me to turn when there is no place to turn. This happens frequently when I am driving parallel and very close to an interstate highway on a service or access road.