iPhone GPS: disabling cell service

[Nathan Hays]

Sorry in advance if this has already been posted – I didn't see it in the first few searches.

I have an iPhone 4 that I use on trail for GPS. The problem has always been that the phone searches for cell service when out of range and that sucks down battery power – a lot faster than if there was continuous cell service. Airplane mode doesn't work because it shuts off GPS.

But I found a way! Turns out, if you lock the SIM card and power cycle the phone, it won't try to access the cell network until you unlock it. Turn off WiFi as well of course. It's a little bit of a pain to go through, but it does work .

I have ATT for which the default sim pin is '1111'. I changed mine to my ATM pin so I wouldn't forget it. Does Verizon use a SIM card? I'm not sure.

BTW, I use Earthmate – it came with my inReach. Really clean topos. I used to use Gaia, but the topos were grainy. You do have to use an app with pre-downloaded maps.

I look forward to trying this in the field soon. I don't think I can keep the sim locked unless I'm actually in the wilds. Not for technical reasons, mind you, but because I gotta feed the net-monkey on my back.

[Jeff M.]

It's out there but you have to REALLY search for it – ask me how I know. ;) Good info and it will be nice to have a separate thread on it for people to find when searching. It's great to not have to shut the phone off quickly after checking coordinates now. Verizon works the same way.

[Jeremy and Angela]

I hadn't realized the newer Verizon iPhones (4S and 5) now take SIMs. It looks like the phones may still have CDMA radios that would work without the SIM, so it'd be good to test things out first.

(E.g. if you have a Verizon iPhone with SIM, try the SIM lock technique and see if you can still make a phone call.)

[Ken Thompson]

http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=50596&skip_to_post=487490

[Nathan Hays]

That's a great link of Amy's. All that info should be in an article on BPL and show up early in a search!

[Richard Nisley]

Has anyone tested this?

[Nathan Hays]

Check out this url that Amy L. linked to:
http://adventurealan.com/iphone4gps.htm
They list some battery depletion numbers they tested.

[Richard Nisley]

Nathan,

The numbers are for an iPhone 4 running on the ATT network. I asked about an iPhone 5 on the Verizon network.

[Jeff M.]

Worked on my iphone 5 (verizon) with an "at home" test. I don't have any battery drain numbers, but it does work. Unfortunately, with little kids I'm not getting out on long trips much right now so someone else will have to be the pioneer and test the numbers.

[J-L]

Even if you can turn off the SIM, wouldn't you want to switch the phone to "airplane mode" to avoid running the GPS all the time? Or does the GPS not actually drain much power with the SIM card turned off?

I usually keep my phone in airplane mode, take it out of airplane mode to check my location, and then switch it back to airplane mode.

[Jason G]

"Even if you can turn off the SIM, wouldn't you want to switch the phone to "airplane mode" to avoid running the GPS all the time? Or does the GPS not actually drain much power with the SIM card turned off?

I usually keep my phone in airplane mode, take it out of airplane mode to check my location, and then switch it back to airplane mode."

If you force quit all applications it wouldn't be using GPS all the time. I bet you could find out from developers if their app still uses gps when the app is closed and/or phone is locked.

I usually do both.. lock my SIM and switch airplane on/off when using/not using. Jailbreaking your iphone makes this all easier too. It allows you to put toggles right on your home screen.

[Ian]

I use the Gaia ap with an iPhone 4S. I ran into something strange yesterday and I thought I'd pass on a couple things I observed.

Went on a hike yesterday where I knew I would have minimal cell phone coverage at the trailhead and that I would eventually lose coverage. Both my hiking partner and I had iPhone 4S but only I was using Gaia. FWIW I don't rely on GPS and my use of it yesterday was just to see how it worked.

After waiting a few minutes, I dropped a pin at the trailhead with the intent of trying to figure out how to navigate back to it once I lost cell phone coverage. I didn't realize it at the time but the GPS was still showing coordinates from a week earlier and 50 miles away. Lesson learned to be extra aware of this when using this feature. I need to play with it more but absent having a map which shows the coordinates of the area I'm in or plotting the coordinate before leaving for the trailhead, it wasn't immediately obvious to me on how I would deconflict this in the field. There was not enough of a cell signal for me to pull up a map and obviously I did not download one to my phone.

I wasn't able to figure out how to get Gaia to navigate back to the pin regardless of where it was located when I was in the field. I figured out later that all I had to do was tap on the pin and an option of "navigate to" would show up. As there was a snafu of where the pin dropped, following the directions would have been catastrophic. My lack of technological savvy is fortunately compensated by my ability to use a compass and terrain association. So far I really like this ap but I understand that I need to become more familiar with it.

Germane to this thread:

After we hiked a few miles into the wilderness, I saw that I didn't have cell phone coverage but my buddy did. I never put the phone in airplane mode and double checked the settings to ensure it wasn't. We both use AT&T and have the 4S phone. After restarting my phone, I had two bars just like he did. I'm not sure if Gaia was responsible for this or not but I learned that if I have an emergency in the woods, to try and cycle my phone on and off to see if I can get a signal. If my hiking buddy wasn't there to tell me he had a signal, I would have assumed that trying to get a signal was a lost cause and probably wouldn't have tried restarting my phone.

[Amy Lauterbach]

Sorry I'm late finding this thread!

I have done a ton of testing of battery drain. I have more info than is in the article Alan and I wrote nearly two years ago: http://adventurealan.com/iphone4gps.htm

To address some of the questions in the thread…

It's out there but you have to REALLY search for it – ask me how I know — Actually, I'm pretty satisfied that if you google the words iphone backpacking the article is right up in second or third place. So if you lose the link you can easily find it again.

All that info should be in an article on BPL and show up early in a search! — Alan and I considered putting it into a BPL article, but opted to host it ourselves so that we could update it on the fly. The data changes regularly, so ability to stay current was important to us. We've revised it 10 or 12 times since we first published it, and it's due for a major revision since iPhone 5 battery issues are significantly different than iPhone 4.

Has anyone tested this? — Oh my, I've tested more than you can imagine. Yes, you can use GPS as long as Airplane Mode is OFF. On any iPhone with a SIM (ATT iPhone 4, or any iPhone 5) you can disable cellular by removing SIM or locking SIM (http://support.apple.com/kb/HT1316). The Airplane switch controls GPS and Cellular in one switch, so it must be left OFF. Verizon iPhone 5 is a very fine tool w.r.t battery drain. My original tests were done with ATT iPhone 4. Recently I retested with ATT iPhone 5, and my brother and DanS both tested with Verizon iPhone5. I haven't had time yet to update the main article, but you can find the bottom-line results over here:
http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=80992&skip_to_post=691474#691474

Even if you can turn off the SIM, wouldn't you want to switch the phone to "airplane mode" to avoid running the GPS all the time? Or does the GPS not actually drain much power with the SIM card turned off? — This is described in more detail in the article. The GPS only drains the battery if an app or a system service is asking for location. It doesn't stay active all the time. In addition to the apps in your app list, you must disable a bunch of hidden "system services" that use Location. There is a superset of battery-draining things in the SETTINGS section of this post (I'm not sure which of these matter, but certainly WIFI, Bluetooth, SIRI, and the Location->System Services, General->Cellular all matter).
http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=80978
With our ATT iPhone 4, SIM locked, we have hiked for 18+ weeks with Airplane mode OFF. Baseline drain with all battery conservation settings in place is 1-2% per day. Same is true for Verizon iPhone 5. But not true for ATT iPhone 5 (as described in the other thread with my test results.)

I bet you could find out from developers if their app still uses gps when the app is closed and/or phone is locked. — you could ask, but in my experience reporting battery-drain problems to several app developers I believe that many of them are oblivious. Best to test the apps you plan to use before you go in the field. Gaia GPS and ViewRanger were the only two apps that responded to my battery drain reports, fixed their problems, and added additional don't-drain-my-battery app settings. Gaia and ViewRanger now give you an option to get a GPS fix only on demand, instead of automatically getting a GPS read when you open the app — that means you can study the map and make route plans without having the GPS running. See more about this in the main article. http://adventurealan.com/iphone4gps.htm

And finally, the folks at my local Apple Store (Palo Alto) know almost nothing about this stuff. When I bought my first iPhone the sales agent assured me that the GPS would not work if I was not in range of cellular signal. When I spent 2 hours with the "Apple Geniuses" last week trying to figure out why the ATT iPHone 5 drains the battery when out of signal range, I was assured by the "Master Genius" that if I turned Airplane Mode ON and also turned WIFI ON that I would get gps services, which is easy to test and is simply not true. WIFI will give an approximate location if you are in range of a WIFI signal, but the gps chip is disabled when Airplane mode is ON. This is a long way of saying that we backpackers are a very small niche market and we care about things that most people don't care about —- Give me GPS when there is no cellular signal and don't drain my battery.

Sorry I haven't had a chance to update the article, which would make it easier for folks to sort through all this info. I'll get to it in the next month.

[Eric Osburn]

Fabulous article on using an iPhone for navigation.

Do you have any updated info regarding the 5S? I'll be upgrading to the 5S from a 4S through my work.

Just curious what the best way to mitigate power drain, and optimize use would be using a 5S.

[Amy Lauterbach]

Eric – The article has battery drain info for the ATT 5 (bad news) and the Verizon 5 (good news). I haven't tested, but also have not heard any reports that the 5S is different from the 5; I suspect there is no functional gps/battery differences between 5 and 5S.
I haven't done any controlled testing of SIM Lock feature in the ATT iPhone 5 since last summer, it's conceivable that Apple fixed the egregious bug w.r.t. locking the SIM, but I doubt it.

http://www.adventurealan.com/iphone4gps.htm

Amy

[Mitchell Ebbott]

I have a T-Mobile iPhone 5S and it seems to have the same problems Amy described on the 5. I haven't done any controlled tests, but in my usage I've found that even with the SIM locked, the battery drains faster than I'm comfortable with. I don't know if it was quite 8-10% per hour, but it was probably at least 5%. Airplane mode dramatically slows the rate of drain.

I'd encourage everyone who care about this to fill out a bug report on Apple's feedback website. Here's the link, and I'll paste below what I put in my report. You can paste it in, write your own, or reword mine however you like. I did file mine under "bug report," not "enhancement request," since this didn't happen on previous models.

Those of us who use their iPhones as cameras, eReaders, iPods, and GPS units while backpacking need a way to turn off all wireless communication but keep the GPS on (airplane mode disables GPS).

In the iPhone 4/4s, SIM lock was a useful way to do this. If the SIM card was locked or removed, battery drain slowed to about 1-2% per day. In user testing, the Verizon iPhone 5 seems to act similarly, draining about 1-3% per day.

ATT and T-Mobile devices, however, have a bug that drains significant battery while the SIM is absent or locked. These devices drain 8-10% per *hour*.

Solutions would include fixing this bug, or adding a "GPS only" mode.

[Amy Lauterbach]

Mitchell – perfect and well done.
I filed my report via the manager at the Apple Store, who said it would be put into the bug system.
Getting attention, however, that's a whole different game. I'm ever hopeful, but not optimistic.

[Dave T]

I might have thanked folks already, but I want to let Amy (and other helpful folks!) know how appreciative I am for all the thought and documentation that has gone into this topic. So thanks!

Sure would love to have a dedicated slider in Settings to enable/disable the GPS receiver, just like Airplane, Bluetooth, Cellular, and Wireless. Maybe they think that users would get confused about how cellular vs. GPS work as locationing tools?

[Mitchell Ebbott]

Amy, can I encourage you to fill out a feedback form anyways? Having worked at an Apple Store in the past, I can tell you that the manager would have escalated this issue through a different system, so having feedback through more than one channel may help.

If we push this, I really do think we might get a fix. I've seen it happen before with bugs and feature requests on this scale where a small community of users has let Apple know that this really matter to them, and Apple has listened. They really do read and care about their user feedback.

[BlackHatGuy]

An interesting article on battery life on iOS7 that some might find useful.

http://www.overthought.org/blog/2014/the-ultimate-guide-to-solving-ios-battery-drain

[Casey Saenger]

My wife and I have been considering replacing our Garmin with an iPhone for an upcoming Brooks Range trip and this has been a very useful discussion. Amy's suggestion that the SIM card be disabled or removed to preserve battery made me wonder if the SIM card was necessary for GPS? I'm currently a dumb phone user and wondered if I could get by with an unlocked iPhone 4 if I acquired Gaia via Wifi before heading out.
Sorry to be so naive.
Casey

[Mitchell Ebbott]

Casey, the SIM card is only for cellular service and is not necessary in order for the GPS to work.

[Amy Lauterbach]

As per Casey's question — Amy's suggestion that the SIM card be disabled or removed to preserve battery made me wonder if the SIM card was necessary for GPS?

To clarify a common misconception: You do NOT need WIFI or Cellular connection for the GPS chip to work; however you do need to have pre-downloaded the map content in order to have your current location show up on a map. You do NOT need a SIM card for GPS; they are separate chips.

The instructions in the article are still true. http://www.adventurealan.com/iphone4gps.htm

[Casey Saenger]

Thanks for the info, and sorry to make folks reiterate what's been typed elsewhere. It is just so contrary to what Dustin told me at the AT&T store this morning that I wanted to be explicit.
Casey

[Amy Lauterbach]

It is just so contrary to what Dustin told me at the AT&T store this morning that I wanted to be explicit.
Too funny. When I bought my iPhone the sales rep at the Apple store assured me that GPS would not work when there was no cell signal. I had read so much that was contrary to that; in the end we agreed that the 30 day return policy meant that I would trust what I read and not what he told me :) I think a big part of the confusion is that if you don't have maps pre-downloaded, then when you open a map app it will look like it doesn't know where you are. Apps like Gaia GPS solve that problem by letting you download all the maps in advance.

And last year when I was working with the folks at the genius bar to figure out the battery drain problem with locking the SIM on an ATT iPhone 5, the "master genius" assured me that I could turn Airplane mode on and GPS would work as long as I had WIFI on. I tested that, and as I expected, it doesn't work — it is true that you get an approximate location as long as you have a WIFI signal, but once you're out of WIFI range then there's no location info.

The iPhone has "Assisted GPS" aka A-GPS . You can read what that means on the wiki article. The iPhone ALSO has standalone-GPS (which is disabled in Airplane Mode) as well as WIFI Positioning system (which gives approx location if you have WiFI signal but are in airplane mode and thus GPS is disabled). WIthout a SIM card (or with card but no cell signal) it will take much longer to get the very first fix after you power up in a new location — in my experience it's as much as 3 or 4 minutes. But after that very first time, it subsequently takes 20 or 30 seconds to get a GPS read. It's good to know about the slow first fix — don't panic, just be patient.

Believe me, we folks who care about 1) battery life; 2) GPS reception; and 3) NOT cell signal — we are so small a group that we are not on the ATT or Apple radar.

[Author]

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