I use a paper GPS, also known as map. Instead of a teeny-weeny screen that makes you scroll endlessly, it has a big one that shows your complete flight plan, as well as alternatives. It allows me to zoom in (and out) in an unbelievable fast rate. Faster than that of any electronic GPS around. It has no knobs or buttons that you can fiddle with, so it will not distract me from the actual flying. It does not make a lot of annoying noises such as 'beep', 'beep-beep', 'beeeeeeeeeep', 'iiiiieew-plop', 'blop', 'bop', 'beep-bop', 'wop', and 'a-wop bop a-loo bop a-lop bam boom', other than 'flap-flap-flappy-flappy-flap' when unfolded in strong winds.
You can draw on it with a pen (a ordinary one, not one of those plastic PDA pens that do not write at all), to insert warnings for téléphérique cables, CATEX (CÂble Transporteur d'EXplosif, real tricky ones!), power lines, restricted or prohibited areas, or anything else you fancy such as altitudes required for a transition. You can even make a thermal map by marking all areas where it goes up! It is cheap, much cheaper than even the lowest of low budget GPS devices. And unlike an ordinary GPS, which contains all kinds of nasty chemicals and metals, you can dispose of it easily in an environmentally friendly manner. For instance by recycling it as toilet/news paper (same thing), or by using it to start a fire to keep you warm during those cold bivouac nights at high altitude.
But the biggest advantage is that a paper GPS does not require batteries, nor re-charging. A current GPS (as well as older ones, that is called progress) works for about 16 hours without recharging (summer 2009). So, your GPS needs recharging after a few good flying days. Especially when you use it during hiking as well. When and how are you going to do that? My vol bivouac trips usually last more than a few days. Should I take along a solar panel and stick it on the back of my harness/backpack while flying/hiking? It all adds weight, and you are probably already aware of my excessive preoccupation with it. So, do not even start about taking along spare batteries. Are you really proposing to carry ten sets of spare batteries when every ounce counts?
My kingdom for a horse of course when I am lost in a deep and dark forest, or when hiking in the dark. Unfortunately a GPS does not work that well (or not at all) under a (thick) canopy of leaves. Neither does it work in narrow valleys without satellites in sight. Surely, I could be lost using my paper GPS as well. But in general this will not last for too long, except in the aforementioned locations. There will usually be enough visible and audible clues to help me determine my position.
I try to avoid hiking in the dark. The night is meant for sleeping. There is a lot going on at night (you will hear all kinds of noises, worrying noises being among them), but there it is not much night life to speak of in the sense of having a party. There is little to see, increasing the risk that I a might bump into something that is hard (to see). It is easier to get lost, even with a GPS. It is safer to sleep at night and hike by day. But if I really need to hike at night, then the stars and moon are there to guide me. A GPS would come in handy when it is too cloudy to see them. But waiting for the daylight is likely to turn out even more handy. That being said, I have met people hiking through the mountains at night without a GPS, but with a frontal headlight. I guess everybody has peculiar tastes that are hard to explain to someone who has not acquired them (yet).
At this point it has probably become clear to you that I will stick to my paper GPS for the moment. That is, unless they come up with a GPS that has the size and weight of a wrist watch, works everywhere, has an operational battery lifetime of two weeks, and a screen that allows adequate flight planning without endless scrolling and zooming.
The fundamental problem is that a GPS tells me things that I already know or can easily find out, except for the precise ground speed. So why take it along? Even when I am flying completely new terrain, I know where I am. I have memorised the geography by studying the map(s). When I am in the air, I verify whether what I see is what I expect. The first cross-country from Chalvet involved a small tour to Cheval Blanc by passing via Sapée, while returning via Côte Longue, Cordeil and Maurel. After landing in St. André, I was perfectly able to describe my route (as well as the alternatives I had in mind), to a more experienced pilot who asked for it. When it became clear that is was my first flight in the region, he seemed happily surprised.
Studying maps for hours before flying a (completely) new area, certainly pays off. It also fun, especially during those grey cold rainy winter days. When you are dreaming of spring, of flying. It is fun to see that the studied flight plan works when you are finally executing it. And if it does not work, you are likely to end up in 'funny' situations as well. It is even more fun to finally see the studied paper mountains for real: "Ah! So your are Cheval Blanc. And that peak over there must be Couard. Oops! The transition looks more challenging than expected." It is like meeting well-known friends that you only know from the internet.
Ground speed is the only parameter that I occasionally miss and would like to have. Close to the ground you have enough clues to estimate it. Higher up this becomes difficult. A GPS will give me the precise ground speed at any altitude, but that is not enough to justify the weight and the recharging issue. Besides, I am not interested in absolute ground speed (the one given by the GPS), but rather the relative one: the speed that allows me to reach my objective. A ground speed of 5,3 km/h does not tell me that much, other than that I have strong headwind. Which I already knew. Or I might be flying backwards since a GPS has no concept of leading and trailing edge.
Verifying my position by using the horizon (or any other far away reference) and a closer reference, gives me constant feedback on my chances of making it past a ridge, of reaching a sunny spot on the other side of the valley, of reaching a field for an emergency landing. Have a look at the vario section for more observational skills and hints.
A GPS could be a lifesaver though. If it has not broken when you crashed into the ground, it could tell you the precise location for the rescue crew (if it has enough satellites in view that is). I count on the rescue team to know the area, so that I can tell them my location by name. Like I said before, it pays to study maps and memorise them.
I do like electronics and other technical stuff, but not in the air. I like to fly free, like a bird. I do not want to be tied to an instrument that tells me what I should do to fly good/effective/fast/optimal. I bet some smart manufacturer reading this will come up with an instrument that has a fun setting (next to the settings for MacReady and sink alarm), playing a cheerful funky tune when you are having fun. The more fun, the more funky the tune! "Yeah, right baby! This thermal is funking groovy!!"
When not strictly needed, instruments are likely to distract me from the actual clues that are there to observe. Clues that are often just as good, and possibly better and more evident, than the information given by the instruments. Did you ever see a pigeon or goose flying with a GPS? Now then, why not try it?
Now that you have managed to read this far, I feel morally obliged to reveal the biggest drawback of using a GPS: the resulting flight log would show me as a mediocre pilot. Possibly worse than that. A pilot that uses vol bivouac flying to mask his incapacity to fly long distances. A pilot that usually hits the deck after a few kilometres and then hikes up again for his next
failureflight. As long as I refuse to use a GPS, I am able to maintain my legendary status as a top gun pilot flying incredibly long distances with two fingers up his nose while maintaining this website at the same time, on the fly.