Diagram of a GPS Satellite Constellation |
Once upon a time in a land
based life, I lived in cell phone challenged Alloway Township. Three different cell phone carriers over a dozen years didn’t improve reception. Since then cell phones and reception have improved.
“Can you hear me now?” has given way to “Can you find me now?” Global Positioning Services (GPS) on Smartphones and vehicle navigation programs have become an essential element in our work and lives.
“Can you hear me now?” has given way to “Can you find me now?” Global Positioning Services (GPS) on Smartphones and vehicle navigation programs have become an essential element in our work and lives.
A recent road trip to visit family in North Carolina, Georgia, and South Carolina, with my oldest daughter and three grand children, got me to thinking about GPS and how much we have come to embrace its benefits. The trip also demonstrated that GPS isn’t perfect and sometimes it doesn’t work.
First, our destination street address, punched into the dashboard device, wasn’t recognized. That’s no fault of the GPS. Mapmakers have yet to plot the entire world including new developments located in what some would call God’s country. My daughter typed in the next locater, Lincolnton, Georgia. The directions got us close to our destination. After that we used the old time method of following niece, Sara from Lincolnton to Petersburg Trace. While the road displayed on the screen, it had no name. As we turned off nameless Petersburg Trace into the wooded area leading to the lake house, the GPS map display disappeared. My daughter and I joked, “Can You Find Me Now?”
What is GPS? What makes it work? What interferes with reception? Can corrections be made to the maps? I just love the Internet. It offers all the answers to the questions above and proves quicker than pulling out a dated encyclopedia.
The official United States government information site (GPS.gov) answered my questions in seconds. According to the site, the Global Positioning System (GPS) is a satellite-based navigation system made up of a network of 24 satellites placed into orbit by the U.S. Department of Defense. GPS was originally intended for military applications, but in the 1980s, the government made the system available for civilian use. The U.S. Air Force has now added additional modern satellites to the mix. There are now 31.
The configuration of satellites is known as a GPS constellation. It’s located 12,000 miles high in the exosphere, a transitional zone between Earth's atmosphere and interplanetary space. The satellites travel 7,000 miles an hour. Powered by solar energy, backup batteries keep satellites running when there is no solar power, in event of a solar eclipse. Rocket boosters keep satellites moving in a dedicated path. Each unit weighs about 2,000 pounds. GPS transmits two dedicated signals, one for civilian use and the other for military use. GPS works around the world, 24 hours a day. There are no fees or setup charges to use GPS. GPS satellites circle the earth twice a day in a precise orbit transmitting signal information to earth. With this information GPS receivers use triangulation to calculate the users exact location.
Technically, the GPS receiver compares the time a signal is transmitted by a satellite with the time it is received. The difference tells the GPS receiver how far away the satellite is. With distance measurements from at least two or three more satellites, the receiver determines the user's position and displays it on a GPS device.
The GPS receiver must lock on the signal of three satellites to determine latitude and longitude when tracking motion. When four or more satellites home in on the receiver an additional factor of altitude is calculated. Imagine trying to explain GPS to someone living in the early part of the 20th century. The concept of something that can determine location, calculate speed, bearing, track, trip distance, and destination distance, sunrise, sunsets and tidal information can only be described as magic or science fiction.
GPS service can be disrupted. Tunnels, mountain passes, heavy clouds and under bridges can interrupt service. When a satellite drops below the line of sight, signals cannot be transmitted. That probably explains why the unit map disappeared when we entered a heavily forested area near our destination.
As for mapping errors, some devices allow one to make corrections on the screen and upload them to the manufacturer. Others offer the same service via the Internet. The changes can take months or longer to show up. The government run GPS service does not supply mapping information.
Every day new uses are found for GPS. The Smartphone has brought GPS into our daily lives. There are tracking apps that map our walks, our hikes, our runs and our biking expeditions. After calculating distance, time and grade the apps can even calculate energy spent (calories).
Backpackers rely on GPS to fix their locations. There are apps that can track a family member’s location in real time. There are units that allow text messages to be sent from location to alert family of one’s well being. Other units allow family to watch the position of a person traveling in real time on a computer, tablet or phone.
Farmers utilize GPS to plant and harvest crops. Pet owners can purchase collar mounted GPS tracking devices to track pets. Organizations with large trucking fleets utilize GPS to track the entire fleet. This allows us to follow packages as they move across country to a final destination.
On Imagine we use GPS to plot our course. We set waypoints, calculatie sailing angles and fuel consumption. We will soon add a mobile GPS satellite messenger to our toolbox. This unit will allow us to text when out of cell phone range. It also includes a SOS feature that notifies a global international emergency response center to begin a search and rescue operation. I’m hoping I’ll never have to ask, “Can you find me now?”