It's a big mystery to me why GPS hasn't a default feature in all higher-end dslrs for many years now. I've tried using an external GPS but that never amounted to anything. Usually the battery would die in the middle of the day (it lasted about 6-7 hours).
IMHO, that is a crappy excuse. Cell phone companies have worked on improving battery life with good results on the latest phones. The camera industry has chosen to ignore this... and as a result, they keep slipping further behind.
… whose battery also does not last a full day when I switch on my GPS.
The battery in my dslr is much, much larger, though. And indeed, some cameras do feature integrated GPS.Your GPS battery life was terrible, yet you can't figure out why DSLR makers don't include GPS as a standard feature?
The GPS on your phone is made better because of the phone. It's called assisted GPS. A camera that isn't a phone has to rely purely on GPS. Apparently that makes a difference.