Another Golden Anniversary: NAVSTAR, the Global Positioning System

The global positioning system (GPS) has revolutionized modern society as well as military operations. This article reviews its fascinating history and highlights some aspects of that history that are not well known. Although now universally recognized as one of the greatest technological achievements of the 20th century, in its early days, the program was almost continually at risk of being cut. The relatively small budget of the initial development program forced the designers to become very creative to meet the system's objectives. An international crisis led to the guarantee that GPS would be available to the world, but security concerns resulted in GPS performance for the general public being severely constrained for several years of operation. Currently, there are four independent constellations providing service worldwide and billions of receivers have been produced at a tiny fraction of the cost of early units.