There’s a fair amount of signal processing going on inside a GPS device.

Modern GPS chips only need around 25mW apparently - older chips can pull 100mW though. Scanning needs a bit more power than tracking.

Is it the same on sport watches? They seem to easily do 24h when doing GPS tracking. That is the popular models there are watches that can track more than 100h (but they always have bigger batteries). This is impressive for me since I remember doing tracking back in 2005 and that meant using lots of batteries.

On phones I think the problem mainly is that the GPS needs to wake up an app that need to handle the GPS data and then do some calculations. You can easily get data ten times a second that is alot of wake up from sleep, and probably draws lots of CPU.

Yes. same chips. I suspect you’re right - it’s not the GPS itself that’s the problem but waking up the main CPU to run whichever App has requested location data.

The phone’s not always using true GPS (reading satellites.) When it does, it uses more energy. In a difficult environment it scans for more satellites than usual, which uses even more energy.

Basically, the phone’s battery life depends on disabling hardware components, or running them in a low power mode, as much as possible.

When people are using their phone's GPS they typically have the screen on (using maps/navigating etc.) more than usual.

I think most of the drain comes from that rather than the GPS unit itself. But people might say "using my phone's GPS uses a lot of battery."