gps systems require a global satellite system to function, used to use the military one but I believe they are putting up civilian stuff now due to the popularity, ie, many more rocket launches. There is nothing earth friendly about satellites, the launches are incredibly toxic, the orbits decay, and require replacing the systems at routine and in terms of human history, almost absurdly short intervals, every step of the process just takes us further away from nature, which to me is the precise opposite of why I go backpacking. Sort of the same idea as not being able to listen to the sounds of nature and needing further stimulation via music player of some type.
However, convenience always trumps any larger considerations in today's consumer society, so there's not much point debating the matter from what I can see. John Muir must be rolling over in his grave nowadays, I feel for his spirit. Backpackers used to care, some deeply, about such questions, but I guess those times are fading now, very sad.
A compass is a piece of metal that points to our north pole, period, with some fancy refinements if you want.
An altimeter is a similarly simple device. Comparing the complexity levels of these different methods is a no brainer, a compass is a simple device, requires almost no support infrastructure to produce, but requires some skill to use well.
I'm not so addicted to cell phone usage that I consider it a necessary item, it sits sort of half way between a basic compass and a gps in terms of the infrastructure required for it to be more useful than a fancy small paperweight, but, like the GPS, is totally and utterly non-sustainable, the peak of human throw-away culture and wastefulness. Happily, looking long term, all such non-sustainable systems must, by definition, be unsustainable, and will fade away, leaving behind a damaged earth and ecosystem, but also leaving simpler tools, not requiring globally complex systems to maintain, that have withstood the test of time, like a compass.