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Tailcoat
04-20-2014, 07:15 AM
Is a smartphone's GPS any good off trail? My character must have a fairly new one since his has a camera flash, but I need him to find his way to a section of forest that has been undisturbed for a century and stay lost for a while without it looking ridiculous.

I can't just have the battery run out since he uses the camera after getting lost.

Helix
04-20-2014, 07:38 AM
Fwiw, I don't have a mobile phone with GPS, but my GPS equipment doesn't work in rainforest because of the density of the canopy. Having said that, it's old ( > 5 yrs) equipment and people who have recently upgraded their GPS sets have told me that the newer ones are perfectly serviceable in dense cover.

This is probably no help.

wendymarlowe
04-20-2014, 08:21 AM
Can you just have him lose cell signal?

melindamusil
04-20-2014, 09:06 AM
Cell phone signal is a biggie. A few ears ago (I think 2010), we were visiting the area where my dad grew up in Middle-Of-Nowhere, Nebraska. The signal was not real strong but ok near the highway. More than a mile or two off the highway, we would lose cell signal and couldn't use gps. Pretty annoying, since those gravel roads all looked the same!

Fwiw: at the time, I was using a blackberry.

Kerosene
04-20-2014, 09:09 AM
I'm confused on what you're using this for. Do you want him to use the GPS on his phone, or not?

I lose cell reception when I'm 5 miles away from civilization. I'll go to Red Rock--which is a five minute drive from a massive casino--and can only make emergency calls.

Helix
04-20-2014, 09:13 AM
Doesn't the GPS in new phones work off satellites rather than a mobile signal? (I don't have a new phone, so I don't know.)

Tailcoat
04-20-2014, 09:29 AM
Can you just have him lose cell signal?
I just looked it up and apparently true GPS isn't dependent on cell service. It seems harder to lose GPS signal. Apparently, you can also download topological maps ahead of time, but I suppose that doesn't matter since he has a paper map which he crumples up in frustration.

I've found at least one phone model with camera flash and no GPS, but I don't want to have to explain that it's the fault of the model and not lazy writing, plus it might come off as too contrived if he just happened to have that one as opposed to an iPhone 4 or something.

If slightly older phones commonly had camera flash and cell-based GPS, that would work. I haven't kept up with phones.


I'm confused on what you're using this for. Do you want him to use the GPS on his phone, or not?
I want him able to use the camera but not GPS. It's an inciting incident where a mysterious hermit sees that he's lost (because he crumples the paper map) and then points the way towards a path. My hermit has been out of civilization for 100 years and ends up puzzling over the stranger's flashing device, which triggers speculation about the outside world. I guess I could downgrade it to a normal camera, but it wouldn't be as mysterious or shocking to the hermit since a non-phone camera at least vaguely resembles its turn-of-the-century antecedents while a smartphone looks nothing like a camera.

WeaselFire
04-20-2014, 10:05 AM
Okay, as a hiker who uses his smart phone as a GPS, it's eminently possible to lose the signal and get lost.

Basics: Cell pones will use both the GPS satellites as well as cell tower responses to locate the coordinates for the GPS location. The satellite signal decreases with blocking terrain, overhead cover and interference from metals. Classic is losing the signal under a bridge, but heavy tree canopy will block the signal as well.

I lose the satellite signals under tree canopy in both the Everglades National Park/Big Cypress Swamp and the Ocala National Forest (Florida boy here). I lose cell tower coverage in the Everglades as well. This leaves me with no phone and no GPS.

That's why I also carry a compass. :)

So, find heavy tree cover, steep canyons and an area not served by a cell tower and your hiker can get lost. Drop the temperature and the batteries start to die as well.

Jeff

Kerosene
04-20-2014, 10:19 AM
Doesn't the GPS in new phones work off satellites rather than a mobile signal? (I don't have a new phone, so I don't know.)

...yes, and no. There's GPS apps out there that can run in offline mode, and apps that can use satellite positioning (pretty much real GPS) to find your location--both of these aren't very accurate. Most GPS apps need the internet. If you don't have those exact apps like BackCountry Navigator, or know how to set your GPS to offline after setting in the directions, you're screwed out in the wilderness--unless, the GPS app runs itself like these without, and I don't know of any that do.
Though, I'm not an expert on this.

Just saw Weasel's post. Yeah, you can lose signal easily.


I want him able to use the camera but not GPS. It's an inciting incident where a mysterious hermit sees that he's lost (because he crumples the paper map) and then points the way towards a path. My hermit has been out of civilization for 100 years and ends up puzzling over the stranger's flashing device, which triggers speculation about the outside world. I guess I could downgrade it to a normal camera, but it wouldn't be as mysterious or shocking to him since a smartphone looks nothing like a camera, while a non-phone camera at least vaguely resembles its turn-of-the-century antecedents.

I think it'll be easy just saying that he can't get cell reception, and his GPS won't find his location. Most readers will be understanding of that.

Or, could you have the screen shatter and go black, forcing him to hit the "camera" button to take pictures and the flash occurs?

Also, most "flashlight" apps on phones use the flash--fyi.

Tailcoat
04-20-2014, 10:32 AM
Thanks. It's good to know I can keep the scene intact. :)

jclarkdawe
04-20-2014, 04:56 PM
I use independent GPS device rather then my iPhone. Latest versions of hiking GPS is an incredibly robust device that doesn't lose the satellites easily.

However, unless you've preloaded detailed maps, it only tells you where you are. It doesn't show trails, small streams, and elevation doesn't tell you much. Depending upon how large the wilderness area is (which depends upon what part of the country you're in), all it might show you is that you're in the middle of a wilderness area, with no idea what direction makes the most sense to travel to civilization.

Cell phone would be unlikely to have a detailed map. If it is an iPhone, the map is likely to be wrong.

All a GPS would show you is your track in, and help you maintain a straight line. But if you think it will help you decide the fastest way out of a wilderness area, you're wrong. And this all presumes that you can take the information from the phone and relate it to the topography around you.

People get lost with GPS.

Best of luck,

Jim Clark-Dawe

cbenoi1
04-20-2014, 06:05 PM
Cell phone would be unlikely to have a detailed map.
That's the main thing. Google Maps (and other similar apps) is based on a tile pulling method, as in it grabs JPG images from the web given a position and resolution requirements. Tiles that are too far from the current position are deleted from the cache and replaced with ones that are closer. Unless you happen to have the right map image in the cache, you're out of luck (*). Garmin makes both iOS and Android apps that have all the map data and POIs pre-loaded. It's a pricey app; most people who would need this level of functionality would prefer a real GPS device instead.

Your Hero might have a valid GPS signal, but no maps to work with it because there is no Internet nor phone connection available. Works fine in the narrative.

-cb


(*) For those of you who have a smartphone and would like to pre-cache Google Maps explicitely on your cellphone, here is the way: http://googlesystem.blogspot.ca/2013/07/ok-maps-cache-this-map.html.

Snowstorm
04-20-2014, 07:22 PM
I don't know if you want your character to have GPS or not, and I don't know where your character is. In Wyoming, if your GPS does work, quite possibly it'll give you wrong information.

jaksen
04-20-2014, 07:44 PM
GPS reliable? Haha. In a densely-populated region on Cape Cod, MA - I am talking postage-size lots with huge cottages on them - our GPS will tell us to take a right on a road which never existed. Then take another left on a road which also never existed into a marsh which still exists. (I guess in the 1940's the plan was to fill in the marsh. Nope, never happened.)

I've also run into people on my road who stop to ask me where another certain road is. (It was supposed to run alongside the shoreline; again, never built.) I have had arguments with people who say but my phone says, but the GPS in my car says...

And I'm saying, keep driving and you'll drive into the ocean. Said road was never built.
(However, to add to the fun and confusion, there were houses built on this nonexistent road and use the road for their address. They access their homes via dirt roads off a different, main road.)

But the map says...

We also lose our cell phone signal inside the house, (Cape Cod), on the first floor, but can pick it up again on the second floor.

Having said all that, the GPS systems are still not 100% reliable, relying as they sometimes do on older maps and systems. Even Google maps is sometimes wrong, misnaming streets, etc., although they don't have roads running through marshland. I noticed one day that our road still had its old name from the 1960's. Now what is that about?

I would say if you are in high country, a mountainous area, yes sure your GPS might not work or be 100% reliable. Haven't people gotten lost on old logging trails and died in the middle of winter because their GPS system sent them down an old road?

melindamusil
04-20-2014, 08:29 PM
I would say if you are in high country, a mountainous area, yes sure your GPS might not work or be 100% reliable. Haven't people gotten lost on old logging trails and died in the middle of winter because their GPS system sent them down an old road?

My stepgrandma used to have a cabin deep in the Colorado Rockies. It was a great little place but VERY isolated. No cell phone signal. No television signal, and too isolated to run a cable television line. You could get satellite television, but even that was not a strong signal due to all the mountains. No land line phone, though there was an emergency satellite phone.

(But it WAS very beautiful, great place to visit.)

Anaximander
04-21-2014, 12:58 PM
I've tried this myself, actually. I go hiking quite regularly, and my phone has GPS, so I've tested it out once or twice. The trick is that your location is calculated by talking to the GPS satellite network, which has pretty decent signal everywhere (although accuracy decreases slightly as you get closer to the poles because of the spacing of the satellites). Unfortunately, that's just your co-ordinates; latitude and longitude. To locate yourself on a map, the map has to be downloaded, and that requires some kind of cell connection - preferably a 3G or 4G signal. You can download the maps ahead of time, and most map apps will cache maps so if it's within the same rough area as somewhere you've looked at before (especially recently), it may still be in memory. Some apps come with internal map data so they don't need a cell connection, but they're often quite large downloads and will take time to install on your phone (I have one that took half an hour to download over my home WiFi).

It's also worth noting that the internal GPS receiver on a phone is not as big or sensitive as the ones you get on proper hiking GPS devices, so you may well have trouble getting a stable signal. Things that can cause you to lose signal include: bad weather, overhead cover (very dense trees, caves, buildings, that sort of thing), electrical interference (power stations or substation transformers, lots of power lines nearby, being within a few feet of a running car engine). You'll also have trouble if you have limited line-of-sight to sky (if you're between tall hills or in a ravine, for example) because the satellites are rarely precisely overhead - the triangulation works best when they're spread out a bit. The more sky you can see, the more satellites you'll be able to connect to, and the better the fix you'll have. You need at least three satellites for a position; the more you have, the more accurate it'll get.

On my phone, here's some typical performance in countryside:
- Thirty seconds to a minute for a fix, after turning the GPS on. (This is known as "cold start" if you want to look up more detail.)
- Usually starts off by giving me a ~100m circle as it acquires the fix, which narrows down to ~10m in two to five seconds depending on the number of satellites it can see.
- Usually you'll get between 5 and 8, maybe 9 (at my latitude, anyway - about 50 degrees). Not all map apps will tell you this statistic.
- With 5 satellites, 10m is about the best accuracy it gets, maybe a shade better; with 8, it's down to about 2 or 3 metres, which takes about 5 - 10 seconds after that first fix, which means a total of 40 seconds up to maybe a minute and a half for it to be settled and really ready for use.

If your character needs to use their phone to get to this place, then you'll need one of these conditions:

- Decent cell connection to download the maps
- The character has looked at the area on his phone map app before (sometime when he had an internet connection) so the maps are loaded
- The character has a proper hiking maps app installed on his phone (rather than just Google Maps or whatever) so it has the maps stored on the phone
- As a last possibility, he has a set of co-ordinates to get to, so he can use one of the GPS apps that reads out your co-ordinates, allowing him to tell whether he's going the right way, but not what the terrain looks like.

If you want him to get there, but be lost for a while along the way, then in a fairly dense forest away from towns and cities it'd be entirely plausible for him to have bad cell reception so he has to wait (or wander around a bit) to get enough signal to download the next patch of map. Note that many systems will download in chunks at varying zoom levels, so it might be that he has a zoomed-out, high-level map of the area, but when he zooms in to get better detail, it pixelates and he has to wait ages for the zoomed-in version to download - or maybe it doesn't, and this lack of detail in the map is why he takes so long.

ItchyDog
04-24-2014, 02:25 AM
Although several posts imply it, here's the reality of GPS & cell phones or other devices: They're different things!
GPS is a satellite system that broadcasts a continuous signal. It's the world's biggest free utility. It provides time and a distance to each satellite in view, then your user device uses that to triangulate your location. It is not a very strong signal, and can easily be lost or jammed (which is illegal). Here's the civilian user site: http://www.navcen.uscg.gov/
And a really good resource: http://www.colorado.edu/geography/gcraft/notes/gps/gps_f.html
How GPS is used/implemented by your mobile device is up to that manufacturer and/or service provider. So, saying the GPS sent you to the wrong location is incorrect. The mapping program that uses GPS sent you to the wrong location. That's pretty common, especially in less populated areas.
So, for the original question, it would be pretty easy for either the GPS signal to be lost due to heavy foliage or a deep, narrow canyon, or because the mapping program is only good in an "urban" environment or the maps of the forest are old (lots of FS maps use a datum older than GPS standard of WGS 84).
BTW, once you've acquired the GPS signal, it's harder to "lose" it, so you could also have your character not try to use the GPS function until he/she is already deep in the forest. It's much harder to acquire a signal than maintain it. But that's pretty deep in GPS-geek territory.