Global Positioning System (GPS) is a satellite-based navigation system that provides location, velocity, and time data to users anywhere on Earth with an unobstructed view of the sky. Originally developed by the U.S. Department of Defense for military use, GPS is now widely employed in civilian applications.

Key Components:
1. Space Segment: A constellation of at least 24 satellites orbiting the Earth, transmitting signals to receivers.
2. Control Segment: Ground stations that monitor and manage the satellites, ensuring accuracy and system integrity.
3. User Segment: Devices (e.g., smartphones, navigation systems) that receive and decode GPS signals to
determine location.

How It Works:
- GPS relies on triangulation, calculating the distance to at least four satellites based on the time it takes for signals to travel. The receiver uses this data to pinpoint its exact location in three dimensions.

Applications:
- Navigation: Real-time directions for vehicles, planes, and ships.
- Emergency Services: Locating individuals during disasters or distress calls.
- Agriculture: Precision farming techniques to optimize crop yields.
- Surveying: Accurate land measurements for construction and mapping.

Advantages:
- Global availability and high precision.
- Free-to-use service for both civilian and military applications.

Despite its ubiquity, GPS faces challenges such as signal interference, multipath errors in urban areas, and vulnerability to spoofing attacks. Emerging technologies like augmented GPS (AGPS) and integration with other satellite systems aim to enhance reliability and accuracy.