Oh, there's way more. Your pictures have metadata. Your pictures have actual landmarks. They have faces of people that have FB location tracking on. The invers

Oh, there's way more. Your pictures have metadata. Your pictures have actual landmarks. They have faces of people that have FB location tracking on. The inverse is also true, pictures from other people with you on them. They can infer from instrumentation if you're sat down, time of day (so probably at home). Download and upload speeds, you're probably on wifi. They buy and sell and correlate data with other companies and advertisers. There's dozens of ways to know where people are. Location tracking on the phone is real time and reliable, but they likely have enough data to ballpark the whereabouts of everyone on Earth!