Do you remember family road trips of years gone by? A designated navigator would sit in the front passenger seat with a map and a highlighter, or with a AAA TripTik, telling the driver what turn to take next.
Fast forward to the 21st Century. The navigator person has been replaced by a screen. Pleasant electronic voices now inform the driver about upcoming turns or traffic congestion.
It’s one more benefit that we earthlings now derive from the U.S. exploration of space. It’s called GPS (Global Positioning System), available on many cars, phones, and even smart watches. But the impact of space-based GPS goes well beyond personal navigation, improving just about every aspect of our lives!
Where Did GPS Come From?
The United States Department of Defense started working on a space-based navigation system in 1973; after lengthy development, it became operational only for the U.S. military in 1983.
However, a tragedy changed everything. On September 1, 1983, the Soviet Union shot down a Korean Air Lines passenger plane that had mistakenly strayed into Russian airspace, killing 269 people onboard.
The need for an accurate navigational system became painfully obvious. Consequently, later that year, President Reagan announced that the military GPS system would become available for any and all civilian and commercial use at no cost. Widespread access was available beginning in 1988. The military would retain its own frequencies.
How Does GPS Work?
GPS has four fundamental aspects:
• A constellation of 24-31 satellites, orbiting the earth every 12 hours at an altitude of roughly 12,000 miles. Each satellite has an atomic clock and continuously sends out signals to whatever receivers are listening.
• Six ground monitoring stations
• Millions of receivers, including navigation screens in cars, cell phones, and smart watches. But there are many, many more. The receivers have an antenna tuned to the satellites.
• Apps. Most receivers include their own apps. Popular others (both android and iOS) include Waze, Google Maps, Mapquest, Copilot, and Apple Maps. There are literally hundreds of others for scores of commercial and personal uses.
Your cell phone is an example of a receiver. To provide navigation information on your location or route to a destination, it must be in an unobstructed line of sight to four or more GPS satellites.
The receiver contains a computer that “triangulates” its own position by getting “bearings” (in the form of time for a signal to travel from the satellite to the receiver) from three of the four satellites.
The Russians, Chinese, Japanese, and Europeans now have their own GPS versions. Their signals can be “read” by the American system.
Who Owns the GPS?
The United States Space Force is responsible for the operation and upgrades of the GPS system.
American taxpayers have funded GPS ($8 billion so far, $11 billion in current dollars). The fiscal year 2024 federal budget includes $1.8 billion for the GPS system
How Accurate is Your GPS (Car, Cell Phone, or Smart Watch)?
That depends on how many satellites are in its line of sight and how recent are the satellites. Generally, it might vary from several feet to a couple of inches.
Just About Every Industry Uses GPS
GPS has become a widely deployed and useful tool for commerce, scientific uses, tracking, and surveillance. GPS’s accurate time facilitates everyday activities such as package delivery, banking, mobile phone operations, farming, fishing, hiking, railroads, weather forecasting, earthquake monitoring, and even the control of power grids by allowing well synchronized hand-off switching.
Self-driving features for cars and trucks rely on GPS. Experts predict that by the end of the decade self-driving taxis, delivery trucks, and passenger cars will be common on American roads.
Sources: GPS.gov, wikipedia, lockheedmartin.com, skybrary.aero, gis2gps.com
