Thursday, December 3, 2015

What is GPS and How Does it Work?

I don’t know why I’m hung up on how stuff works this month, but GPS is another one that is worth being knowledgeable about. A good GPS system has advantages over using your iPad or similar tablet as a GPS, specifically, no cellular signal is needed to load maps, and we will talk more about this in a moment.  An RV GPS, like the Rand McNally, works by using the Global Positioning System (GPS) put into place by the U.S. Department of Defense in 1973.  The space-based navigation system works in all weather conditions as long as there is an unobstructed line-of-sight to at least 4 or more GPS satellites.  The U.S. government created the system, maintains it and provides it for free to anyone that has a GPS receiver; it does not require Wi-Fi or cellular service.   GPS consists of 3 segments: the space segment, the control segment, and the user segment. 

The space segment consists of the 24 to 31 GPS satellites orbiting the earth, each maintained by the U.S. Air Force, which are responsible for broadcasting signals from space to a user’s GPS receiver.  They are strategically arranged into 6 orbits so that at any given point on earth, at least 4 satellites are visible at all times.  Makes you wonder what the Government can see us doing, huh?  Each satellite orbits earth twice per day at about 12,500 miles above earth.



The control segment of the GPS consists of a master command station located at Schriever Air Force Base in Colorado Springs, Colorado, 12 command and control antennas, and 16 monitoring stations located all over the planet. 



The basis of GPS is time.  Each satellite is set to an atomic clock and are checked daily by the control segment to be sure they are synchronized with each other.  Their location is also checked daily; if one is not correct, the control segment removes it from the system, corrects its location, and returns it to the system.  The U.S. has committed to having at least 24 GPS satellites available in the system to users, although they have currently have 31 operational satellites in orbit.  Better to be safe than sorry, right?

The user segment of the GPS consists of the receiver, like the Rand McNally 7730 or Rand McNally RV Tablet, which receives the signals from the satellites and uses them to calculate location. By using current maps downloaded to the receiver, the Rand McNally is able to use this information to help with navigation. 

Our GPS receivers in our RV are receiving at least 4 signals from satellites at any given time and through this, can calculate our 3D position which includes longitude, latitude, and altitude.  It can also determine speed (or time).  It does this by using a process called triangulation - I know this is getting deep, but stick with me here.  By taking the location of three different satellites, it overlaps their positions and where they meet is the location of the receiver, or user. 



Rand McNally GPS System vs. Phone GPS 

A lot of people as us, "Does our GPS system require Wi-Fi or cell signal to operate?"  The Rand McNally does not require any Wi-Fi or cellular signal to operate the GPS; however, if you would like to have up-to-date weather, traffic and fuel price updates, you must enable Wi-Fi on your system.  Although your cell phone is using the same exact GPS satellites to navigate, using Google maps on your phone or iPad is not the same as using a Rand McNally and does use data to navigate. The reason for this is that your phone is not pre-loaded with the maps like the Rand McNally is, and it is having to download the map as you drive; it does this by using your data.  Because of this, if you lose cell signal while traveling then your Google maps on your cellular device will not work properly. Unfortunately the low cellular signal areas are probably the very areas that you need assistance with navigation because it is far away from a cell towers and probably on the back roads where turning instructions are crucial. Many people think they can save money and just use their phones to navigate, but be aware that simply using Google maps on your phone can drain your data throughout the month, drain your phone’s battery, and provide poor instructions in low cellular signal areas.

Regardless of what GPS receiver you use, you will always encounter occasional routing issues.  No GPS is perfect 100% of the time. There are some things you can do to ensure that your system sends you the correct way. If you have problems with your receiver, always check to be sure you have the latest maps downloaded.  The Rand McNally 7730 and RV Tablet 80 both come with free lifetime maps. In addition to updated maps, check your settings to see what you are telling it to avoid, such as tollbooths, highways, u-turns, dirt roads, etc.   Finally, some travelers compare the route given to them by the GPS to a road atlas before leaving to ensure the GPS is correct; the RV Tablet 80 has a road atlas app built-in for this convenience. 

To learn more about the Rand McNally 7730 or the Rand McNallyRV Tablet 80, visit us at www.technorv.com or contact us at support@technorv.com