×

We’re currently experiencing some technical difficulties that may result in some difficulty placing orders. Please direct order questions or issues to support@sparkfun.com for us to work with you on resolving. We’ll respond to emails as quickly as we can in the order they were received. We are working on getting everything fixed as quickly as we can. Thank you for your patience.

Apis

Member Since: July 31, 2011

Country: United States

  • “Why four? You would think you only need three for triangulation, right?"
    GPS determines position by trilateration, triangulation involves angles (see wikipedia). You need 4 satellites for 3D trilateration and 3 for 2D trilateration, no need to consider time. GPS uses time to measure distance to satellites though.
    The 2D case is easiest: if you know the distance to a satellite (of known position) you know your position is on a circle with the satellite in the center and the radius equal to the distance. Two satellites gives two circles, your position will be on the intersection which is usually 2 points. A third satellite will give you a single point. In the 3D case one satellite gives a sphere, two a circle, three two points and four a single point.

No public wish lists :(