GPS was Initially developed for military use, which is now part of everyday life; used in mobile phones, in car navigation and search and rescue equipment. It can provide your location, altitude, and speed, However,as we know that GPS is not accurate all the time, sometimes it losses signal and cuts out on their users, eventually leaves them in middle of nowhere. So over here, I will talk about why is GPS data sometimes inaccurate?
Not enough satellites
GPS typically need to receive signals from at least 7 or 8 satellites to calculate to within about 10 meters. With fewer satellites contributing, the amount of uncertainty and inaccuracy increases. With fewer than 4 satellites, many GPS receivers are unable to produce any location estimates, and will report “GPS signal lost”. The GPS unit is usually looking to find and acquire signals from more satellites, so should eventually recover from situations where not enough satellites are found.
Buildings, trees, tunnels, mountains, clothing, and the human body can prevent GPS signals from the satellites reaching the receiver.It is better to just put a GPS receiver in a place where it has a clear and unobstructed view of a large portion of the sky. However, sometimes the obstructions are unavoidable, like in downtown areas where tall buildings block view of the sky, in dense trees or driving in the tunnel.
When signals from the GPS satellites bounce off buildings, the GPS receiver can be confused by the extra time the signal took to reach it. In these cases, you may observe sudden large errors in position. This is why when we walk around in city while using GPS in the phone to navigate, it sometimes shows sudden large errors in position.