[astrange]

You don't need cell service for the GPS to work, it's a GPS and should work anywhere with open skies. But you would need an offline map to use it for something, and that map had better not tell you an impassable road is drivable.

Satellite connection in the new iPhone should work anywhere in the US for emergencies IIRC.

[msrenee]

If you had the foresight to download maps for the area you got lost in, then it might help. The you still have everything that compromises the GPS signal. Proper GPS units indicate how many satellites are available and you can work out how accurate the positioning is from there. Keep in mind big landscape features can bounce the signal around.

Basically, it could be helpful in the event that you've got the maps available to you and you're already somewhat familiar with how to use a GPS and what their limitations are. Also, keep in mind how often your navigation app tells you to take an exit off the highway when you're actually on the frontage road. It's a tool, but it's not magic. Someone linked the Chretiens' story. They had a GPS unit, but not the understanding of its limitations. Relying on it was what went wrong in their situation.

I fall back to a road atlas when I need to navigate outside of town if I'm not on the interstate. It just works. Topo maps for hiking and a compass. If you know how to use them, it takes 99% of the guesswork out of the equation.

[ghaff]

"Proper" GPS units don't magically have maps, especially detailed ones, either.

And, especially for driving purposes, knowing things like the number of satellites locked on and how many feet of precision you have isn't very relevant.

I agree that in general backup topo maps and a compass are useful in any case.

But even maps are not magic. The knowledge that a "road" on a map may not be something navigable by a normal vehicle and driver or that a military base won't have a perimeter regularly patrolled by soldiers requires knowledge that a map won't give you.

[msrenee]

I feel like we're bouncing between contexts here, so I'm going to try to organize my thoughts a bit.

A proper GPS unit will give you a lat/long reading as well as additional information that can help you determine how accurate those numbers are. This can be referenced on a topo map and to help determine your location in addition to landscape features. The accuracy of the GPS location is quite important as the difference between thinking you should make a slight turn onto a road that turns into a minimum maintenance quagmire and knowing you should stay on the visually identical main road can easily be measured in meters.

As far as whether cell phone navigation features could help people in these situations, they would have to already be prepared and familiar with its use. In many or most cases like this, the affected individuals were unfamiliar enough with what they were getting into that they would not have had the maps downloaded before finding themselves out of reach of cell signal. Without the maps downloaded, they'd be pretty much out of luck.

Even if they had the maps downloaded, there will be no real-time updates on road conditions as there is no cell signal. Most of the maps I've downloaded in the past didn't come with information such as roads only being passable at certain times of year. I know there are maps out there with that level of detail, but you'd have to have planned properly and made sure the maps were up to date and had the relevant details. At which point you probably wouldn't find yourself in the situation in the first place.

I've left this point alone so far, but your battery will not last for long trying to use it while outside of cell range. You can turn off all your data, wifi, etc, if your phone can decouple that from GPS availability, but it's still a lot of screen time and battery use. At some point, you're out of juice. It's more of a time constraint than a functional constraint, but it's something to keep in mind should you find yourself in this situation.

Basically, if folks are prepared for the situation, the cell phone navigation would probably help. The majority of people who wind up lost down a back road were not prepared and the cell phone nav wouldn't help.

[ghaff]

I can't get the number of satellites out of iOS but I can absolutely get a lat/long and accuracy. (Android you can get the number of satellites.)

Yes, you need to know how to use your phone and download the appropriate app(s) and maps while connected to the Internet. And you should probably have an external battery pack.

And many people won't prepare before setting out. But I'm not sure how different that is from a dedicated GPS unit or even map/compass. The only thing I use my ancient dedicated waterproof Garmin GPS for is sea kayaking so I don't risk my phone.

[msrenee]

I guess it just comes down to preparation then. A cell phone with maps downloaded is probably more convenient than a GPS with maps downloaded. I just don't think it's going to help much for the sort of situations that are being discussed in the thread where adequate research and planning were not done even though those things (albeit in less digital form) were absolutely available at that time as well.