Figure 4.
The timeline traces the development and adoption of Global Positioning System technology for surveying from the late 1970s to around 2015, while also highlighting key system level milestones. It begins in 1978 with the launch of the first Block 1 satellite, followed by development and testing activities during the 1970s and 1980s. In 1983, the United States government commits to making Global Positioning System signals available for civilian aircraft, and the first commercial receivers for surveying become available. During the early 1990s, surveyors begin using differential and stacked Global Positioning System techniques, and in 1992 the satellite constellation reaches full operational capacity with 24 satellites in orbit. In 1994, the National Geodetic Survey launches the Continuously Operating Reference Stations network. Adoption of real time kinematic methods begins in the 1990s and expands further after 2000, when selective availability is disabled, leading to improved positioning precision and widespread civilian use. Additional milestones include the launch of the Online Positioning User Service in 2000 and the adoption of virtual reference stations by surveyors in 2002. The timeline also distinguishes between partial civilian access under selective availability before 2000 and full civilian availability thereafter, illustrating how technical and policy changes collectively enabled broader and more accurate use of Global Positioning System technology in surveying.Timeline of relevant events in the history of GPS in surveying in the United States