From Space With a Purpose

When I think GPS, or Global Positioning System, I think “Help me get to the pizza place via (insert address) I give you. I wouldn’t be wrong, although there are far more important purposes and uses for it than pizza. From its conception today, not much has changed with regard to its process, yet the market for its use continues to grow. So long to the days of writing down directions and printing them out, or using the north star and celestial landmarks. All I need is a GPS device and I can get guidance on the go from any place on Earth. I believe GPS has the assumption from people of being this Top Secret complex and confusing process algorithms monitoring every time I go out for pizza. And with this data about my position, there must be law and order to protect my privacy. According to Nasa, “Global positioning System or GPS is a United States space-based radionavigation system that helps pinpoint a three dimensional position to about a meter of accuracy…” (1). That’s pretty damn close if you ask me, considering I’m 6’2”, which means it can pinpoint a three dimensional position twice around me, if only it worked that way. How does it work? First, let’s talk about its history moment, we’ll get to the good stuff soon, and trust me, it’s not as complicated as you may assume.

Science Behind The Magic

"Essentially, the GPS receiver compares the time a signal was transmitted by a satellite with the time it was received. The time difference tells the GPS receiver how far away the satellite is.” (5). GPS navigation we commonly use like in our car and cellphones are installed to receive the produced radio frequency signals from the satellites. From this data, our location is determined relative to the strength of the frequencies of each satellite. Similar to you hearing a car coming down the road, you can determine (estimate) how close or far it is from the strength of its sound, relative to your position. The change in pitch is called a Doppler effect.


There are 40 satellites orbiting that provide signal, with around 30 always active, and at least 4 are visible to you no matter where you are, providing you aren’t under a cave that blocks the signal from reaching you. This information was found and summarized from AirForceTV on YouTube, “BLUE Episode 10: Space - The High Ground” (6).

Each satellite transmits their location and time at specific intervals, from this signal, your location can be determined. From Garmin, “A GPS receiver must be locked on to the signal of at least 3 satellites to calculate a 2-D position (latitude and longitude) and track movement. With four or more satellites in view, the receiver can determine the user's 3-D position (latitude, longitude and altitude).” (5) With regard to what exactly the satellite is transmitting, “A GPS signal contains 3 different bits of information”, an “I.D. code that identifies which satellite is transmitting information.” Ephemeris data, which “…contains important information about the status of the satellite (healthy or unhealthy), current date and time.” And almanac data, which “… tells the GPS receiver where each GPS satellite should be at any time throughout the day.” (7).



GPS is not just a satellite, or few of them. It is its own network, or constellation, specifically placed to maintain adequate coverage of earth. And we aren’t the only team on the field, both Russia and Europe have there on constellation of satellite coverage, known as GLONASS GPS and Galileo Navigation Satellites, respectively."


Conclusion

GPS is a powerful tool with a simple concept. From pizza deliveries, to military combat, and to animal research and study, its purpose is broad and serves as a valuable tool to us all. I probably relied on my GPS navigation unit for the first couple weeks navigating through Richmond to VCU. Without a doubt, I would have turned down many one-way roads if not for my navigation unit to guiding me. Technology is advancing, with the latest edition of GPS III set for production and use, service will only become more accurate. With this accuracy and power, there should be established laws and protections for the citizens.