GPS itself isn’t the issue. Devices like smartphones are GPS receivers only, meaning they can only receive GPS signals. It’s what those devices do with GPS that’s the actual problem.
The thing is, smartphones can be tracked by multiple methods. You can locate them via cell tower triangulation. And to a lesser extent even WiFi tracking, Bluetooth tracking, etc. So if you really don’t want to be tracked then turn your devices completely off. Or better yet leave them home.
GPS does not track anything. There is no possible way it can.
GPS satellites transmit time coded signals. That’s all they do. They don’t receive any signals from the devices that use them.
GPS receivers (which include everything from car navigation systems to smartphones to dedicated GPS receivers, etc) only listen for those time coded signals, decode them, and use that information to triangulate your location. That’s all that GPS itself can do.
Smartphones, tablets, etc. can determine their location by GPS if they have GPS receivers built into them. They can then take that location data and forward it on to companies like Google, Apple, etc. But that is done over either a cellular or WiFi connection.
Any claim of GPS based counting of crowd sizes should be taken with a huge grain of salt. The only way counts based on mobile phones could really be done is by asking companies like Google or Apple how many of their devices are being tracked in the area, or by asking mobile providers like Verizon or AT&T how many mobile phones are connecting to their cell towers in the area.
The total number of people/ devices identified by GPS in a given area is exactly 0. Because GPS by itself is simply incapable of doing anything like that on it’s own.