You open the map, and the blue dots appear almost immediately. How does it know where you are? The answer may be contrary to intuition: it's not the satellite staring at you, but your phone calculating its own position.
Positioning satellites, whether GPS, Beidou or other systems, will continuously broadcast their location and time to the ground. After receiving these signals, the mobile phone multiplies the signal propagation time by the speed of light to obtain its distance to a certain satellite. The satellite doesn't know who you are, it just keeps sending out its own "business card" that any receiving device can receive.
Why do we usually need at least four satellites? Because you can only measure the distance to one satellite, you can only confirm that you are on a sphere. Two satellites provide two spheres, with their positions reduced to one circle; After three satellites, there may only be two points left. The role of the fourth satellite is not only to supplement the quantity, but also because the clock in the phone is not accurate enough, and the time error needs to be calculated together.
A positioning process roughly goes through the following steps: satellite broadcasting signals, measuring time differences with mobile phones, calculating distances and rendezvous, and then calibrating with a fourth satellite. The entire calculation is done in the phone and chip, and the satellite does not participate in calculating where you are.
Satellite signals are often obstructed in places such as basements, shopping malls, and high-rise buildings. At this time, the phone will also use base stations, nearby Wi Fi hotspots, and motion sensors to assist in calculation. So you can still see the blue dot, it just drifts occasionally.
Ultimately, mobile positioning is not about someone watching you from the sky, but about your phone listening to several signal sources that can tell the time at the same time, and then calculating the location yourself. Understood this, next time the blue dot drifts, you will know to take two steps towards the window.
Disclaimer: The information provided in this article is for general informational purposes only and is not intended as a substitute for professional technical advice or consulting. Always seek the advice of a qualified professional with any questions you may have regarding your technology decisions. Never disregard professional advice or delay in seeking it because of something you have read on this website.
