Which system was developed by the US Department of Defense in the early 1980s as a navigational tool?

The Global Positioning System (GPS) was developed by the US Department of Defense in the early 1980s as a navigational tool. Its primary purpose is to provide accurate location and timing information anywhere on Earth, utilizing a network of satellites that transmit signals to receivers. By triangulating signals from multiple satellites, GPS technology allows users to determine their precise geographic location with remarkable accuracy.

This system has transformed navigation across various sectors, including military applications, transportation, aeronautics, and personal navigation. The introduction of GPS has facilitated advancements in mapping, civil engineering, and even everyday technologies such as smartphones. The reliability and effectiveness of GPS have led it to become the standard for navigation and positioning on a global scale.

The other options refer to different systems or technologies that were either developed for other purposes or have different functionalities. For instance, the Global Navigation Satellite System encompasses various satellite-based navigational systems, of which GPS is one. Geostationary Satellite System generally pertains to satellites that remain fixed over a specific point on Earth, which is distinct from the purpose of GPS. Dynamic Positioning System relates to marine technology used for maintaining a vessel's position using its own propellers and thrusters, separate from the navigational capabilities of GPS.