These days, you would see GPS watches of different brands and styles everywhere. Each boasting of competitive features and functionalities that promise to help you progress on your fitness journey. But are you among us who wonder how do GPS watches work?
How Do GPS Watches Work?
Your GPS watch uses, well, GPS to get your exact location through triangulation, which is the process of determining the difference between the time that your device receives a signal from satellites, and the time when that signal is sent to your device.
The GPS receiver, which is integrated into your GPS watch, will then use this data to determine how far your device is from the satellites. Your GPS watch will measure a series of points to calculate metrics such as speed, pace, and distance accurately.
What About the Satellites?
So, how do satellites work in space, and how are they related to GPS? A network of 24 satellites with known positions orbits the earth in a precise path to send microwave signals to GPS receivers which then use the data for triangulation to determine your exact location.
A GPS receiver needs to detect at least four satellites to be able to calculate your longitude, latitude, and elevation. Note though that the more satellites in view, the more accurate the results are. This process happens continuously, measuring time lag and distance from the other satellites in relation to you as the GPS receiver in your device keeps track of them as you move.
What About Elevation?
An elevation measurement is a distance between the surface of the earth and a point below or above it. But because the earth’s surface is constantly changing and is full of physical anomalies, scientists tend to rely on vertical data which are abstract representations of the surface of the earth.
You can get elevation information from your GPS device. Many fitness devices or watches make use of barometric altimeters to get accurate readings and measure the pressure changes from different elevation levels when you exercise or workout so that you can get real-time elevation change data.
What About Accuracy?
There are times when you have ran the same route as your buddies, but your devices show different readings. You may be thinking, “Why did it give me a different distance?” or “How come I took way more steps today than yesterday on the same route?” Here are some possible ways that cause the discrepancy:
- Different Device Model
Among the major reasons could be because you use a different device model which uses a different process of receiving, filtering, and logging GPS signals.
Additionally, the quality of the antenna, which detects the signals provided by the satellites, and the number of tracking channels may also cause this discrepancy. Unfortunately, there can even be larger discrepancies if you traveled long distances.
Some devices also have battery-saving options which can decrease the accuracy of measurement from your GPS. Other devices also use satellite orbit predictions which provides data for a short time and can be refreshed when a data connection is used.
- The Satellite Position
As previously discussed, the more satellites used, the better the level of accuracy is. These satellites orbit Earth, and so the number of satellites in view fluctuates. Hence, this is a factor to consider when it comes to accuracy.
If you wish to record a track, then it is best to do so twice or more and then get the average of the results.
- Your Location
GPS needs a direct line of sight between the satellites and the receiver to get strong signals. However, when there is an object that blocks or reflects these signals, it takes time for them to arrive at the GPS receiver resulting in a minor time delay.
Moreover, if you are using your GPS watch in a new area for the first time, then it can take a little while to locate you compared to a previously tracked location. How well your device picks up and adapts to the current constellation on the area will result in getting your first fix sooner.
What Causes Interference?
The GPS uses radio signals in frequencies that are reserved for navigation services. And as mentioned earlier, to ensure that the GPS service continues to work smoothly, the frequency or the spectrum needs to be protected from any interference.
Again, the problem can occur when signals of the same frequency interfere with one another or if there is an object in the way. Among the objects that can affect the signal frequencies are buildings, mountain slopes, car roofs, tree covers, and even human bodies.
Your GPS device can also record a different path from the same place or route during summer compared to when it is winter.
What Are GPS Alternatives?
If GPS is to the U.S. Department of Defense, then GLONASS is to the Russian Aerospace Defense Forces.
GLONASS has satellite systems meant for high latitudes, which GPS systems cannot reach. In that sense, while it has not fully replaced GPS as this one has ground stations worldwide, GLONASS makes for an excellent alternative for signals in other parts of the world. Hence, it is highly suggested to use devices with receivers and antennas that can pick up GPS and GLONASS signals for the most accurate information.
Other alternatives include Galileo Positioning System of the European Union and BeiDou-2 of China. Both systems are expected to be in full service by 2020.
With its growing popularity, it is not surprising that one may ask “How do GPS watches work?” Well, GPS devices, in general, can be a little complicated for us to comprehend. However, regardless of what GPS device you use and what your reason is for using one, we can say that GPS helps us in a lot of ways, from tracking your progress on your fitness journey to mapping out your lost vehicle.
But let us also keep in mind that it is not perfect. Some factors can affect its accuracy, so it best not to rely too much on the information that it provides and make it our responsibility to use this information with precautions.