Maybe check https://www.blm.gov/maps/georeferenced-PDFs for coverage.

I expect the BLM maps would be at least as detailed as Google and probably better.

Yes, IF you have an actual GPS device. My point is that most people's mapping on their cell phone is running off the cell network, not the actual GPS network, so will fail once you lose signal. Including mine. :)

I primarily use paper maps and a compass, to be honest. It might be old-school, but it still works if my batteries die.

EDIT: OK, I stand corrected! I just am the old guy who hasn't updated my phone in forever. My iphone 4 doesn't cut it apparently... But my paper and compass really does work.

Smart phones generally have a dedicated GPS receiver (with support for several satellite constellations). A smart phone dependent on the network for positioning would be an exception at this point (they certainly use the network to speed up location acquisition and improve precision, but they are not dependent on it).

But what can happen while traveling into new areas is that whej data link drops the mapping ap blanks, rendering the gps fix less than useful and giving the impression that the device is dependant on data coverage. Most phones have a facility to pre-download maps to cover this situation but you need to know to do it.

GPS receivers without maps are still perfectly useful if you have appropriate paper maps. And even if you have a dedicated GPS receiver with maps you need to pre-download maps as well.

By all means have paper maps and a compass as a backup but I doubt there's a smartphone on the planet today that doesn't have a built-in receiver for GPS satellites. They may (probably do) also use WiFi and cell signals to speed GPS reception but they're in no way dependent on those other signals for GPS tracking unless they can't pick up a GPS signal indoors etc.

Can be worth getting a second-hand GPS watch as another option. Lightweight, useful and you are probably already carrying a powerbrick to charge your phone anyway so that covers recharging overnight.

Um, what? A satellite-based GPS? As opposed to a GPS that doesn't use satellites? All GPSes are satellite-based.

Google Maps plus some satellite images is usually pretty good, and of course nothing beats being prepared. (Bring MUCH more water and sun protection than you think you need!)

Google Maps is terrific on pavement. Get off pavement in the Rockies and no, it is about 80% accurate. Good enough to make you think it is going to lead you right... until it sends you completely wrong. Believe me, those of us who spend our weekend off-road in the West are painfully aware of exactly where Google's limitations lie.

I spend a decent amount of time exploring strange parts of the world, and in my experience with several different phones in several different countries is that GPS (assuming your phone is charged and you're not in a cave/underground) is always good enough to get you out of wherever you are.

To give some examples, in the past twelve months or so I've navigated by GPS (using Google Maps to visualize my position) in mountains in Iran, semi-rural Ukraine, forests in France, middle-of-nowhere Canada, and forests in America. In case you think that my GPS worked just because I had good devices, I've used everything from a nice iPhone 6+ to a decent Galaxy S5 to a crappy Huawei P8 Lite which I bought for $65 used.

I'm not sure how you can quantify GPS as "80% accurate". Does that mean 20% of the time it puts you in the next state over? Or that it's 200 meters off? I can't think of a reason why your GPS position would be wrong... it's not as if physics just breaks down in the Rockies.

In order to get such tremendously poor results, I have a feeling that you did something like turning off GPS (which forces your phone to rely on cell tower triangulation) or using GPS where it doesn't work (like in a cave.) If the actual, raw values from your GPS were wrong I would be extremely surprised.

The 80% accurate statement is about the maps themselves. Google maps will show a road that just doesn't exist. Or you will be driving down on a road that isn't on the map. Or the map will show the road going through, even though you are at its end, looking at a cliff. It will show intersections that do not exist.

In some cases, I can tell they used old data. I know one road in particular that did exist 30 years ago, but the forest service deliberately closed off when a rock quarry closed, and it has been re-forested. It still shows on the maps. Another that shows on the maps was planned to be built by the BLM, but never was... yet the map shows it. So I'm not sure exactly what data set they built their maps from, but clearly it did come from data, not actual exploration... because the dirt roads in the American west are just not accurate.

In general, the information on maps about dirt roads in the US West can be hard to rely on. Some of the information, as you say, is just out of date.

But it's also the case that dirt roads range from well-maintained and graded to you'd better have a jeep and know how to drive it--and the distinction isn't always obvious on a map (digital or otherwise). Road conditions also vary based on season, weather, and how recently there's been maintenance work done.

Someone stated in an earlier discussion that part of the issue is that a lot of this dirt road data is from US Census TIGER data, which was never intended for automotive navigation. [1]

[1] https://news.ycombinator.com/item?id=11657931

The accuracy statement is about the maps.

Google Maps can be pretty spartan in wild parts of the US.

I would suggest getting a "Benchmak Maps" atlas of the state you are traveling in. About $25 each. The whole state at 1:300,000 with comprehensive coverage of many features. You will find all the dirt roads and many trails. Good for driving into and around the back country. For hiking, especially off trail, I prefer good old 1:24,000 USGS maps.