GPS navigation can sometimes display an inaccurate position even with a good connection due to electromagnetic interference, physical obstacles, or delays in receiving satellite signals.
GPS signals come from satellites that orbit very high above our heads. As they pass through the ionosphere (the electrically charged layer of our atmosphere) and the troposphere (the weather layer close to the ground), they undergo quite a few disturbances. These atmospheric layers act somewhat like a magnifying glass that slightly bends the signal's trajectory. The result: the travel time of the signal varies, and your GPS sometimes ends up displaying a less accurate position, even with a good connection. Ionospheric disturbances are especially strong during solar activity peaks. Humidity, storms, and temperature variations in the troposphere also play their part by slightly altering the speed of GPS signals, making you believe you are a few meters away from where you actually are.
The multipath phenomenon occurs when GPS signals bounce off buildings, mountains, trees, or any other structures before reaching your device. As a result, your receiver picks up multiple signals coming from different paths instead of just the one arriving directly from the satellites. Consequently, your GPS can get confused and display a position that is slightly off from its actual location. This often happens in cities, surrounded by tall buildings, or near cliffs, where reflective surfaces are abundant. Even with a good network, this phenomenon causes location errors, varying in significance depending on the environment around you.
Sometimes, electromagnetic interference disrupts your GPS navigation unexpectedly. Your smartphone receives radio waves from many other sources: telecom antennas, Wi-Fi hotspots, radios, high-voltage power lines, etc. All these sources generate electromagnetic noise that can overlap with the signal received from the GPS satellite. As a result, your device ends up lost amid these disturbances and misinterprets its actual position. Even an excellent internet connection doesn’t help: having a signal doesn’t prevent these invisible interferences from causing chaos between the satellites and your precious GPS.
The GPS uses digital maps to locate your position and guide you. When these maps are no longer up to date, you can quickly find yourself off track. For example, if a new road has been built, if a street has been altered or even removed, or if a traffic direction has changed, the old data no longer matches reality. You may then end up displayed in the middle of a field or even in a river: nice, but not very practical. Even details like a recently added roundabout are enough to disrupt the accuracy of the navigation, and your GPS app suddenly seems lost without any connection issues being responsible. A good tip: regularly update the maps to avoid these hassles.
GPS satellites use hyper-precise atomic clocks to measure the time it takes to send a signal. However, even they are not perfect! Over time, a small time drift occurs between the time indicated by these clocks and the actual time on Earth. Even a tiny error of a few microseconds is enough to cause shifts of several meters in the calculation of your position. To correct this, ground stations constantly monitor these discrepancies and send corrections to the satellites. But if an update is delayed, you may temporarily receive an incorrect position, even with an excellent connection.
To accurately determine a position on Earth, GPS systems must simultaneously receive signals from at least four satellites. If only three satellites are detected, the GPS can at best provide a rough estimate, which is often less reliable.
The minimum accuracy offered by the civil GPS system today is about 5 to 10 meters. However, military GPS benefits from specific technology that allows it to achieve an accuracy of one meter or less.
When we talk about a 'good GPS connection,' we are referring solely to the clear reception of satellite signals and not to an Internet connection. Thus, even without Internet access, a device can theoretically determine its position using only the visible satellites.
A time measurement error of just a microsecond (one millionth of a second) by the atomic clocks of GPS satellites can lead to a positioning error on Earth of nearly 300 meters.
Yes. The military GPS system uses a complementary frequency and specific encrypted codes, allowing for accuracy generally better than 1 meter, compared to 5 to 10 meters for civilian commercial systems.
You can improve accuracy by keeping the GPS device as visible to the sky as possible, by enabling additional services like GLONASS or Galileo, or by using a specialized device equipped with a high-sensitivity antenna dedicated to positioning in natural environments.
Generally no, unless it is made of metal or contains electromagnetic components that could cause interference. In that case, the phone's GPS antenna may have difficulty receiving the satellite signal clearly.
With a good signal, the accuracy of consumer GPS is generally between 5 to 10 meters. However, this accuracy can vary significantly depending on atmospheric conditions, electromagnetic interference, the quality of the maps, and the number of satellites your device is receiving.
In a tunnel or any heavily covered area, GPS signals cannot reach your device. Your GPS then relies on an estimate, and when it finally picks up satellite signals again upon exiting the tunnel, it has to recalculate your exact position, which can take a few seconds.
This phenomenon comes from multipath propagation: the GPS signal bounces off buildings, mountains, or reflective surfaces before reaching your receiver. These reflected signals create distance errors calculated by your device, which distorts your actual location on the map.
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