The Tab has wifi and bluetooth, but it does not have built-in cellular data.

It comes with a USB port, and I would suspect, though I don't know, that it'd let you connect a cellular data adapter to it. Do you have a chance of getting cell reception where you want to go?

The Tab has fulltime GPS, and I think I recall a display at one time saying it had acquired 24 satellites. At other times it's been as few as 4, and then there's a warning saying that accuracy was degraded to 100 meters. (How ironic...Magellen would've killed for 100 meters accuracy, and to us it's "degraded".) Seems to be fully-capable GPS. Came with a turn-by-turn navigation app, too, but I haven't tried it. Not sure I'd want to be distracted by it while driving.

The wifi thing I was telling Tom about is a way of making up for GPS when you're in the dirt for resolution. Or if GPS stops working for some reason. But it's only useful in densely-packed urban areas. Not much wifi on the Sierra trails, I'd imagine.

I haven't really figured out the onboard maps thing. I get a map display when I'm out walking most of the time, but sometimes all I see is a pin representing me on a blank field (I hurriedly look around to make sure I haven't actually been transported to some Euclidean plane). I definitely don't get Google satellite overlays or any of the enhancements without wifi. I'll play with it some more and get back to you.

Open wifi seems to be ubiquitous wherever there are dense knots of humans exchanging money. Most notably StarBucks, and there are what, like 23 million StarBucks in the US? At the nearby quaint old business district, I can start with free wifi at StarBucks, and end up eating lunch two blocks north at a Subway while surfing the Net on wifi from the BevMore next door, with the Peet's across the street my backup wifi. All legit, they offer it to the public and require you to accept a terms of service the first time you connect, and then they send you to the store Web site. After which you're free to use it as you will.

The wifi won't be of use to you in the wilderness. You'll still have GPS and stored maps, and also stored materials like books, Kindle or otherwise, and music and other stuff in the big microSD card you want. Even videos to watch at night out on the trail. Or stream through some rancher's open wifi. Damn, are we living in the Federation?

After all that, I forgot the most important thing: Battery life. I'd say that if you run the whole three-ring circus, you'll get maybe six hours. OTOH, mine can go a couple of days when all I do is read the newspaper and check a couple of apps. Bluetooth uses more juice, lots of data transmissions use juice, keeping the display on most of the time, and especially leaving it set brightly, eats electricity.

If you really want to take this thing on the trail...hmmm, yeah, might be doable. Battery is integral so you can't take along spares to swap in. It gets power through the USB port, so you might be able to locate a solar panel with a USB output or adapter.

Hope this is helping (and not confusing things).