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Old Jul 22, 2009, 12:12 PM   #1
Wishsong
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ipod touch GPS?

We're going on a vacation where we will drive around a lot, and we need a GPS. But we also need something to keep the kids occupied for an hour or two, so an Ipod touch is ideal. Is there any way to use one as a GPS without wifi? Probably not, just wondering....
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Old Jul 22, 2009, 01:22 PM   #2
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Nope. There's no physical GPS chip inside an iPod touch. It gets its location using WiFi triangulation. TomTom has a car-mount GPS system for iPhone and iPod touch users. The mount adapter itself has an embedded GPS chip far more accurate than the iPhone's. Maybe opt for that? I'm sure if it will be released in time (or if it already is) for your vacation.
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Old Jul 22, 2009, 01:42 PM   #3
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You can buy a Garmin Nuvi 205 or 255 for about $ 175 and they are excellent.
I'd wish the Touch had a true gps chip, but so far nope.
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Old Jul 22, 2009, 03:56 PM   #4
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So wait.... if I get that GPS mount thing, how does that work? Come to think of it, I don't even know how a real GPS system works.... does it have all of the data installed or does it need connection?
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Old Jul 22, 2009, 04:45 PM   #5
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Oh jings where do we begin?

Right, proper GPS like my hand held Garmin device that I use stands for Global Positioning System. It talks to GPS satellites, at least 3 of them launched by the Yanks but as many at 10 at one time (there are 24 in the sky but you can't see them all the time due to curvature of the earth issues.) These satellites have atomic clocks and all send out a pulse at the same time. Knowing that the satellites all send out a pulse at the same time, and their approximate position on a given date and time, and that the speed of radio waves and therefore light is a constant (allegedly, some guy called Einstein has other ideas...), by judging the difference in time it takes for the signal from one satellite's signal to reach you compared to another (and a third for good measure), compare the difference in time (microns of a second) and using a complex bit of Greek mathematics (known as trigonometry or triangulation), you can estimate your position on Earth to around plus or minus 5 metres.

GPS on an iPhone or mobile phone is a bit of a fake, but any mobile with the right software can work it out. It doesn't use the GPS satellites but everybody knows what GPS does so it uses it's genericised trademark. What it's doing is triangulating it's position using signals based on the time it takes for pulsations from 3 microwave base stations (mobile transmitters if you will) to be received by the phone. If you know the position of the transmitters (and it does) the you can work out your position to around plus or minus 20 metres.

Read this if you want more info.
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Old Jul 22, 2009, 08:26 PM   #6
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Originally Posted by Fuzzy14 View Post
Oh jings where do we begin?


GPS on an iPhone or mobile phone is a bit of a fake, but any mobile with the right software can work it out. It doesn't use the GPS satellites but everybody knows what GPS does so it uses it's genericised trademark. What it's doing is triangulating it's position using signals based on the time it takes for pulsations from 3 microwave base stations (mobile transmitters if you will) to be received by the phone. If you know the position of the transmitters (and it does) the you can work out your position to around plus or minus 20 metres.

Read this if you want more info.
You were doing so good with your first paragraph, then you post this nonsense. The GPS chip in the Iphone can and does use satellites to find location, it just can use wi-fi and 3G when it cant get a good signal from the satellites to approximate your location (inside a building for instance), it also uses 3G (if available) to get ephemeris data and the almanac. A couple quotes from apples site here to help you out.


"But the A-GPS (Assisted GPS) solution on iPhone 3G goes a step further, using a unique approach to find the closest satellites and more quickly identify your position. That gives you a faster fix on your location than with regular GPS. "

"In addition to A-GPS, iPhone 3G uses signals from GPS satellites, Wi-Fi hot spots, and cellular towers to get the most accurate location fast."

Source:
http://www.apple.com/jp/iphone/features/gps.html

So lets stop with this whole iphone doesnt use satellites nonsense. If you have an Iphone, pull the phone chip, turn of the Wi-Fi (or be where you cant get it) and it will still find your location once you get satellites locked in.
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Old Jul 23, 2009, 06:15 AM   #7
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Let's give Fuzzy the benefit of the doubt.

The iPhone (no suffix etc), also known as the iPhone 2G, does not have GPS. It relies exclusively on WiFi and cell tower triangulation. So if Fuzzy was being pedantic with the naming scheme, then the statement is correct, if somewhat misleading.

As you noted, the iPhone 3G does use real GPS satellite tracking where available, but it uses the assistance of WiFi and/or cell tower triangulation to speed up the process of getting its initial fix on the satellites, and to get a fix where there is no effective line of sight at all.

So you're both right.

To the OP:
Quote:
Come to think of it, I don't even know how a real GPS system works.... does it have all of the data installed or does it need connection?
GPS by itself is a purely one-way flow of information, from the satellites into your GPS receiver. The result of this communication and the associated mathematics is essentially two numbers, a latitude and a longitude. During the entire process of computing these two numbers, no data ever flows from your receiver back into the GPS satellites (or into any other computer system, for that matter).

With GPS substitutes such as WiFi and cell tower triangulation, there may or may not be a requirement for two-way communication of data in order to calculate your position. But the effective result is the same, a latitude and a longitude.

Once you have the latitude and longitude, it's up to the specific implementation to do something useful with the information:

-The oldest stand-alone consumer GPS handhelds literally just displayed the latitude and longitude on the screen, and left it up to a human navigator to plot their position on a paper map.

-Some applications (such as tracking devices) actively transmit the resulting latitude and longitude back to a central service to keep track of the equipment's location.

-Some services (such as the Google Maps application on the iPhone) attempt to plot your location on an electronic map, but the maps are stored on a remote server and the device needs a two-way data connection to download them on-demand.

-Other GPS handheld appliances or applications (such as TomToms) keep a copy of their maps right in the device, so they can plot your position without needing to download any further data. These maps are typically limited to a certain geographical area to keep storage space requirements reasonably small.

Last edited by goosnarrggh; Jul 23, 2009 at 06:35 AM.
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Old Jul 23, 2009, 07:24 AM   #8
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Modern consumer GPS devices can store the entire US and Canada maps in the GPS. They also use SD cards preloaded with maps. There's no technical reason why an iPod couldn't have a true GPS chip and pre-loaded maps of the entire US. However, I'd prefer the stand-alone route.
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Old Jul 23, 2009, 03:19 PM   #9
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You were doing so good with your first paragraph, then you post this nonsense.
Thank you for your constructive critisism. The op wanted a description of what is GPS and how it worked, which I provided. The term 'GPS' has been heavily abused by devices that perform a location finding function. Since I own a iPhone 2 and an old school Garman boat GPS I am aware of the functionality and operation of each, but I didn't know the iPhone 3GS contained an actual chip that talked to satellites, lesson learned.
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Old Jul 24, 2009, 11:37 AM   #10
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Okay thanks guys! You guys explained it so it was really easy to follow (I wasn't confused in the slightest). So if the 3rd gen ipod touch had a GPS chip, it would probably kind of suck right? Unless you were in a wifi area (which you probably won't be if you're driving) and there isn't good access to a satellite, you're basically screwed.
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Old Jul 24, 2009, 12:24 PM   #11
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You usually get pretty good access to the sats everywhere. Only place you tend to have problems is inside buildings.
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Old Jul 25, 2009, 07:16 PM   #12
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Originally Posted by Fuzzy14 View Post
Thank you for your constructive critisism. The op wanted a description of what is GPS and how it worked, which I provided. The term 'GPS' has been heavily abused by devices that perform a location finding function. Since I own a iPhone 2 and an old school Garman boat GPS I am aware of the functionality and operation of each, but I didn't know the iPhone 3GS contained an actual chip that talked to satellites, lesson learned.
You are welcome. If you own a Iphone 3G (ie 2nd generation Iphone, which I thought you meant by Iphone 2), its GPS chip uses satellites as well, in fact the Apple site I sent you was about the Iphone 3G. Given the changes in 3.1 version of the OS, I think it extremely likely we will see the $2.25 GPS chip in the new Ipod Touch.
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Old Jul 25, 2009, 10:55 PM   #13
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The result of this communication and the associated mathematics is essentially two numbers, a latitude and a longitude.
Not at all trying to be pedantic, but since we're really trying to nail this down and get to the truth of the matter, GPS systems, in general, triangulate your position in 3-dimensional space. They use this to determine not only your lat and long, but can also determine your altitude.
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Old Jul 25, 2009, 11:12 PM   #14
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Okay thanks guys! You guys explained it so it was really easy to follow (I wasn't confused in the slightest). So if the 3rd gen ipod touch had a GPS chip, it would probably kind of suck right? Unless you were in a wifi area (which you probably won't be if you're driving) and there isn't good access to a satellite, you're basically screwed.
No, not really. If the 3rd gen touch has a GPS chip, it should be OK without WiFi as long as it can see the satellites, which it will be able to if in the car.

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Originally Posted by sandman42 View Post
Not at all trying to be pedantic, but since we're really trying to nail this down and get to the truth of the matter, GPS systems, in general, triangulate your position in 3-dimensional space. They use this to determine not only your lat and long, but can also determine your altitude.
Every GPS device I've owned seems to have issues with altitude though. The altitude will fluctuate about +/- 20 feet or so while the device isn't moving and obviously not changing altitude. So it can be used for altitude if you want a general idea but I certainly wouldn't want an airplane I'm flying on to rely on GPS to get the altitude.
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Old Jul 26, 2009, 06:30 PM   #15
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Consumer GPS is intentionally "off" by 10 or 15 feet. The Govt. doesn't want terrorists buying something off the shelf with more precision than that. Join the armed forces though, and you'll see that their GPS devices can pinpoint you to within a few inches on earth.

Will the 3rd gen Touch get GPS? I believe Apple wants the Touch to run as many iPhone apps as possible. It would add 13 million or so potential customers for iPhone app developers. But the Touch already has a WiFi-based location ability. It's not great, but it's enough to make an iphone app work that wants location info. For that reason, I doubt GPS is a priority for the 3rd gen.
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