That is to say, when you use location-related services after turning on the phone, iPhone can determine your approximate location through cellular mobile network search (based on the information fed back by the signal base station) and WiFi networking (the geographic location information of WiFi). This is explained in detail in "About Location Services and Privacy ..." under the "Location Services" switch. If the phone is turned off, in remote areas (such as subways and underground garages), GPS may not be able to penetrate), which will affect the positioning of cellular networks. Of course, the iPhone's GPS is powerful enough to locate accurately in most cases except the above environment. Conclusion: In other words, when GPS is not available, cellular and WiFi are used to assist positioning. If you rarely go where GPS can't penetrate, you can turn it off. Suggest opening. After all, in case, ...