So the kids and I have taken up geocaching. Fun little outdoorsy activity.
But I sometimes get frustrated about the accuracy of the GPS function in my iPhone. I’ve tried to look up information but, being the web, the contradictory information is enormous. Is there any hard info about it?
Or should I get a handheld GPS instead?
It can put me not only in my living room, but on the couch. That said, the chips used in these things are pretty standard; I doubt a handheld is going to do better.
The main accuracy difference is in how fast it can get a signal. The 4s gives me a half-mile radius almost instantly (and sometimes incorrectly) based on the cell tower; it can take a 30-90 seconds after that before it gives me a precise location (which I’ve never seen to be wrong, except in places that can’t see the sky like an underground garage).
I used to use a GPS-based app (RunKeeper) on my iPhone 3S for mapping my runs. I’d get very frustrated with the (in)accuracy of it; it’d frequently round off corners, miss turns, etc. When I’d go into the RunKeeper site online to fix the map, I’d often find I’d be “adding” about 10% to the actual distance I’d run, just by making sure that the map of the run right.
I now use a Garmin wristwatch GPS; IME, it’s a lot more accurate for my use, and I nearly never need to “fix” a map, the way I did with the iPhone. The Garmin requires some time to get a good GPS “lock” before you start using it; that can take several minutes. But, once it has that lock, it seems to be very accurate.
The accuracy is as good as any other GPS device, assuming it can get a signal - a few meters, perhaps. What may be lacking relative to dedicated devices is the refresh rate (which would cause the rounded corners in a track), and the time to achieve that accuracy (it will display less accurate information until higher precision is available, and this may take upwards of a minute)
Beyond the accuracy of the GPS, there is the accuracy of the maps to consider. Some start out with significant errors, but even the best degrade with age as new roads are built, freeway interchanges are re-done or eliminated, etc.
Less so when using the aerial photos, but roads get re-routed, rivers change course, etc. so even if the photos were dead on when taken, they may not be so hot when you need to use them.
Where my Garmin shines is in the sticks, when I can get one bar in the hot spots and no chance for 3G data. Having topo maps on-board makes it useful, where the phone would be worthless, and good navigation is way more important there than in a city where you can’t look at a map without a local stopping to offer help.
Of course you may simply have a bad GPS chipset. Apple had to replace one of my previous iPhones due to a bad chipset. It was always off on my location - always. Eventually via the Genius Bar at my local store the replaced the entire phone free of charge and I never had another issue as long as I owned that phone.
Okay, I’ll admit I may just be paranoid but my wife was recently in Chicago on a business trip and I awoke in the middle of the night with a bad feeling - worry about her safety mostly. Well, I used the app and it had her probably 10 - 20 miles inland from where she was supposed to be staying on Michigan Ave. on the Magnificent Mile.
Is it possible the app could be that far off or is it time for me to worry about a wandering spouse?
I’ve never really used the Find My iPhone app much, but is it possible it could just be showing the last known position? If the phone is switched off or unable to get a signal, could it still be showing an old position?
GPS’s altogether are not particularly accurate in short amounts of time. On the move, you are likely to only get accuracy to within 100 feet if your lucky.
Professional equipment can give you precision to the hundredth of a foot or better, but you must hold it place for about an hour or so. 15 minutes will get your position to within a few feet.
Professional equipment tracks several satellites; on a consumer devise, you may only track the bare minimum, which will cause it to take even longer to find your position. Software or other settings may limit how often it updates your position, too, making it still longer to find your position (but also saving battery life).
If the person leaving the cache used a consumer device, its position is only as good as the device he used. Your device, being of similar quality, would likely only get you to within 50 feet of the cache if you’re patient.
You and your kids would have to resort to good ole’ fashion scrambling to find the treasure!
Maybe overall. But if I sit on my front porch with the Maps application open on my phone, the GPS will find my location in about 90 seconds with an accuracy sufficient to drop a rock on my head (say, about a foot) every time I’ve tried it.
I’ve got a Motorola/Android and use Google MyTracks for hikes and walks. Ambles, really. I almost always get accuracy to within two to five feet. The little tracks and charts have some wobble: if I walk exactly straight east on a level paved road, the diagram shows me meandering…a little.
I get about the same accuracy in town, where there are cell towers, and out in the boonies, where I don’t have any phone coverage, but still get GPS (presumably from satellites.)
I’ve never had an error as large as 100 feet. But now I know it’s possible, I’ll be less astonished when one happens.
By “on the move”, I was really thinking by car. At car speeds, 100 feet is usually negligible. For hiking, I suppose you would be moving slow enough that it would still be tracking and updating.
However, I am confused by how you determined an accuracy of 2-5 feet. Could you clarify?
I don’t even carry my handheld GPS when I’m out geocaching anymore. My iPhone is plenty accurate enough. The thing to remember with geocaching is that the original hider had some inaccuracy when placing the cache and now you are looking for the geocache with some inaccuracy. Sometimes the inaccuracies add up in such a way that you are yards away from the cache. When geocaching, in just about every case, once you get to the where your GPS says is the spot, it’s better to just drop your pack there and start an ever widening search instead of trying to chase your GPS around.
I last bought a handheld GPS in 2003. Its performance was starting to degrade, so I thought about buying a new one. For the price of GPS, I got a 7 inch Android tablet instead. The tablet blows a handheld GPS or smartphone away in terms of screen size. Just install a mapping app and free topo maps of the area you will be hiking and you will never go back to a dedicated handheld GPS. The handheld sits on the shelf while the tablet gets used for something, like browsing this board or reading a book, nearly everyday. The only advantage a handheld has over a tablet is battery life on an extended backpacking trip.
IDK, but I have a Geocaching tip for when you are not getting a good read. Use direction, not distance. Get about 100 or so ft from the location and note the compass direction of the cache (draw a mental line) Then get another spot again about 100 ft away and draw another mental line to the cache. Where those 2 lines meet will be a good indication of where the cache coordinates are. You can add as many lines as you want, just try to find the center point. The more lines typically the better.
In other words circle the cache, noting the direction at each point and try to find the intersection based solely on direction at the points and not distance to the cache.
Ah! That makes sense; sure, at 100 mph the accuracy is going to be different from at 3mph.
For accuracy, I note how close I am to certain obvious visible landmarks on the trail. On Google Earth, for instance, you can zoom in and actually see individual large isolated trees. If the GPS shows me standing at the base of the tree…and I’m actually doing so…that’s pretty darned accurate.
(If I were claiming accuracy with respect to lines of longitude and latitude, I would be arguing in circles, for how do I know that Google Maps has those lines drawn correctly? But when it comes to something physically visible, that’s an objective measure of accuracy.)
All GPS implementations are not created equal. Some chipsets use more satellites, some use GLOSNAS to improve accuracy, some listen for additional satellite signals that will correct for distortion caused by the atmosphere.
I’d have to look up what they stuck in the iPhone, but if it’s par for the course for Apple, they probably installed a decent and high quality solution, but they didn’t install the most accurate solution available because the best implementations are probably expensive, large, and eat more power.
Do any of these devices (phones, watches, hand-helds, whatever) have a port for an external antenna? Do the manufacturers offer either an antenna or at least a recommendation for a third-party antenna? Specs for what a useful antenna would look like, electronically?
IIRC, the problem with GPS accuracy was the number of satellites it could reach, and refresh as you traveled. Something small enough to wear on my wrist doesn’t have room for much of an antenna.
That’s unlikely, but I can see a situation where she’s inside, unable to get a GPS signal, and this the phone is relying on Wi-Fi position data to determine her location. That info can be hilariously off in some cases.
Can you easily manually turn off the GPS on an iPhone?
On Android you can; I usually leave mine off since GPS is a big battery suck. And when the GPS is off the phone makes location guesses using I believe cell towers and WiFi. Which can, as mentioned, be hilariously off. For instance it might notice she’s connected to the Comfort Inn wifi and decide therefore she must be at Comfort Inn headquarters.