1. GPS cannot locate 100%, let alone believe in the lies of indoor positioning; GPS is not like mobile broadcasting, where signals can be received anywhere. Many things can affect GPS satellite search, including the distribution status of sky stars, buildings, overpasses, radio waves, leaves, grid paper, etc. There are too many things that can be affected. Generally speaking, the area of the sky visible from the GPS position is the area that GPS can receive signals.

　　2. Do not use it once or twice, or for a day or two, to determine the quality of GPS; Due to the different satellite states in the sky every day, it is possible that the same location may receive full data in the morning, but cannot locate at night. It is also possible that the positioning situation may not be good for several days in a row.

　　3. To compare the quality of GPS, it is necessary to compare it simultaneously with the same location; Many people when buying a new GPS will say things like, "The one I used before was better," but this statement is incorrect because the results are significantly different due to different usage times and locations. It is necessary to use it for a long time or at the same time and location to feel the differences between the two types of GPS.

　　4. The GPS reception intensity table is no longer sufficient as a reference for GPS purchasing; When people buy GPS, they only look at the receiving meter in the electronic map. It used to be quite accurate, but now GPS has fake signals or simulated signals to make the receiving meter look good. The receiving meter is indeed very beautiful, but maybe the positioning is not accurate, and even it cannot be displayed accurately.

　　5. There is no GPS for indoor positioning; Basically, if there is no signal indoors, it means there is no signal. True indoor positioning starts from cold start, but if it can still be located, it is true indoor positioning. However, indoor positioning is basically meaningless because I don't know how to navigate at home.

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