Question

To uniquely determine the position of the user using GPS, one needs to receive signals from at least

• A. \(1\) satellite
• B. \(2\) satellites
• C. \(3\) satellites
• D. \(4\) satellites

Hint:

GPS positioning requires solving four unknowns: \[ (x,\;y,\;z,\;\text{clock error}) \] Hence, \[ \boxed{\text{Minimum satellites required}=4} \]

Answer 1

The Correct Option is D

Concept: The Global Positioning System (GPS) determines a user's position using trilateration. A GPS receiver must solve four unknowns:
• \(x\)-coordinate.
• \(y\)-coordinate.
• \(z\)-coordinate.
• Receiver clock error. Hence, signals from at least four satellites are required.

Step 1: Understand GPS positioning. Three satellites can determine position only if the receiver clock error is already known. In practice, the receiver clock error is unknown.

Step 2: Determine the minimum number of satellites. Therefore, \[ \boxed{\text{A minimum of four satellites is required for GPS positioning}.} \] Hence, the correct option is \[ \boxed{(D)\;4\text{ satellites}.} \]