Thanks, but I also own TomTom. I haven’t opted for in-app traffic data. It’s not something I experience often, for which I’m very happy.
I also use Navigon (and will use Navigon Europe on my trip next month). I also did not opt for the extra fee for traffic "info", for the same reasons, and I've heard it's not quite ready for prime time. Not sure where TomTom and Navigon get their traffic data, but I know many companies are working (and Apple also, as announced) on a better way to gauge traffic. If it were really accurate, gathering speed and location info on thousands of cars, then I would feel it would really be useful for urban commuters, since you can only have so many Eye In The Sky helicopters, or people analyzing cams around the city, to be that confident that if you choose a different route to work/school, etc, you will really save time, gas, and hassle.
Ok. So according to the Wikipedia article, my numbers are correct. While it prefers four, it can use three for a quick and dirty fix, and it can use more for redundant information. And as eight are visible at one time, it can use up to eight.
The only thong about the article that's not quite correct is the current accuracy. It's much more accurate than 65 feet.
If the number of discovered satellites drops to fewer than 4 you will lose gps fix. At least four are required to maintain positional estimates.
Any app that you permit to access your location can create its own database (remember, receiving location information is one of the permitted background activities). However, the app would not start tracking after a restart of the iPhone until you start the app for the first time (there are no login items in iOS).
We need to know whether these apps are allowed to keep any of this info. I tend to doubt it, as they have to ask each time. I don't remember any app stating that they were keeping any of the info, except for mapping apps such as my GPS app. And we're expressly telling them to do so each time.
I think people just assume it?s three satellites for GPS because of the association with triangulation, even though it?s multiple triangles that all confer using a network of triangles.
Quote:
Originally Posted by muppetry
Many units include status indicators showing satellites detected and satellites locked..
That is how my Garmin works. I see each satellite as it is detected and slowly locked. As soon as I have three it displays my location on the map. This experience along with the documentation included with the device lead be to believe that only three satellites were required. I did notice that it sometimes would display the elevation incorrectly. I first noticed this when descending a steep route to sea level. Now I understand that it must be reusing my last known elevation in lieu of a fourth satellite.
I also use Navigon (and will use Navigon Europe on my trip next month). I also did not opt for the extra fee for traffic "info", for the same reasons, and I've heard it's not quite ready for prime time. Not sure where TomTom and Navigon get their traffic data, but I know many companies are working (and Apple also, as announced) on a better way to gauge traffic. If it were really accurate, gathering speed and location info on thousands of cars, then I would feel it would really be useful for urban commuters, since you can only have so many Eye In The Sky helicopters, or people analyzing cams around the city, to be that confident that if you choose a different route to work/school, etc, that you will really save time/gas/hassle.
Even when you have accurate flow data, if there's a delay of even 5 minutes in delivering that info to your mobile device, the traffic data may no longer be reliable, depending on the cause of the reported traffic issues.
Yes, once position has been established, then it's "the more the merrier" for accuracy, but on a declining scale. Once you've got 6 or 7 sats identified, adding another two or three more doesn't improve the accuracy all that much. Perhaps from an estimated 12' down to 9-10'. But the accuracy of the gps location isn't the big variable. It's the quality of the maps the device uses. All maps used by consumer gps devices are rift with positional errors.
As for how many satellites are generally used for navigation, it's common for 8-11 satellites to be "found" by modern gps navigation devices within a few minutes at most.
This is what I've been saying, and you've been telling me no to. Though, as only eight satellites are line of horizon at any one time, I wonder how the receiver sees more than that number.
If the number of discovered satellites drops to fewer than 4 you will lose gps fix. At least four are required to maintain positional estimates.
I assume that's only if you're moving though. Theres too much evidence that shows that only three will locate you accurately, at least to horizontal position without elevation data. As the article shows, the assumption is that you are on the earth's surface if you are below 11 miles.
Straight, to-the-point mea culpa. I say this as someone who was vehemently demanding something like this (despite having taken much abuse from this forum).
All is forgiven!
In all fairness the “abuse," which I recall was simply disagreeing with you, wasn’t against you requesting Apple respond to the issue or making the changes they said they would make on these bugs — which I would qualify more as parochial coding not a bug — but with other aspects of your hypothesis.
I wish I understood better why GPS needs a WiFi hotspot database to be speedy. GPS originally was for military applications right? Missile tracking and such. Surely such a system does not take, as Apple claims, "several minutes" to return a result?
Aren't those satellites constantly broadcasting - surely you just need to listen for a second or two? Or was the system built with the assumption that the thing you are locating is high and fast moving?
Once a device has acquired its location and it remains in contact with the satellites, location updates are very fast. All military equipment simply will stay connected constantly (except submarines that is).
As far as I remember assisted-GPS provides you with the precise position of the satellites your GPS device is communicating with (and indirectly thus which of the satellites are ones that should be communicated with because they are in best position). The data connection to the satellites is fairly slow (hey it is a pretty old system), the main data sent from the satellites is very precise time signals, as the travel time of the signal depends on the distance between you and each satellite, you can from the travel time and the position of the satellites calculate your position. The satellites also send their position but receiving that takes longer than the pure time signal.
For those that really and truly want to understand what your GPS device is telling you and how it works, pay a visit to GPSReview.net
A friendly, active and patient forum with exceptional knowledgeable members and moderators. There's already been too many wrong assumptions posted in this thread to take up more time from the original subject.
To MStone: Watch more closely the next time your gps boots up. You won't have a lock at three satellites. They lock in so quickly it's sometimes hard to catch. If the sat bar is solid it's locked. If hollow it's only found but not yet usable for navigation purposes.
To Mel: The article you're relying on is incorrect on several statements. Wander on over to GPSReview,net one day when you have time.
But if they're broadcasting it, how can they stop anyone who wants looking at it?
Encryption, there is an additional encrypted signal that contains more information which increases accuracy. The military has the key to decrypt it, you don't have it.
Now that we are told the phone keeps the information for over a year, they are going to turn it off?
Too bad. I got a kick out of seeing where I had been, and like photos, and a journal, helped me remember things I had forgotten.
Sounds like a great app we could install that would maintain a history for us.
I'd think that it would be fairly simple to write an app that people could voluntarily use to do precisely what you're suggesting. The trick would be writing it such that it didn't become a battery drain.
We need to know whether these apps are allowed to keep any of this info. I tend to doubt it, as they have to ask each time. I don't remember any app stating that they were keeping any of the info, except for mapping apps such as my GPS app. And we're expressly telling them to do so each time.
Yes, they will explicitly ask you every time you start them up. But Apple cannot tell apps to 'forget' any data, it can only reject apps that store data but do not make that clear to the user.
Agree completely, though I think it's a fairly seamless transition from SNL to the US Senate. (The Senate's funnier of course.) Too bad we never did get a Senator Blutarsky.
Calmer minds have noted that Franken's questions are totally appropriate from the viewpoint of the non geek world (i.e. most people.)
If this episode sheds light on the 24-hour homing device that most of us carry around, then its a good thing. People need to be conscious of the implications of technology... most aren't.
I'd like to see people also be reminded that the FastPass on their dash tracks them even more closely.
There's no conspiracy theory, it's just obvious that Google is lying because their "inadvertent" excuse isn't credible when you consider they had to be seeing all the private data they collected go into their database for years.
There is absolutely no similarity between these issues.
Yup....There is a huge difference.
These are locally stored files (on your computer) which after the bug causing the data to be saved for 1 year, uptil 7 years, would probably have increased in size by a few mb. Its the same data, just that the automatic cache flushing algorithm was wrong.
OTOH, Google was picking up data that was completely irrelevant, and they didn't need in the first place. They specifically had to write code for it, it being something they didn't need, and collecting of which is illegal.
That is how my Garmin works. I see each satellite as it is detected and slowly locked. As soon as I have three it displays my location on the map. This experience along with the documentation included with the device lead be to believe that only three satellites were required. I did notice that it sometimes would display the elevation incorrectly. I first noticed this when descending a steep route to sea level. Now I understand that it must be reusing my last known elevation in lieu of a fourth satellite.
I’m still and will likely always be amazed that we have the technology in our lifetime to get such accurate data.
1903 — First powered flight
1953 — First supersonic flight
1957 — First human-made object orbits Earth
1959 — First human-made object lands on Moon
1961 — First manned mission to space
1962 — First communications satellite to direct relay TV broadcasts
I was amazed that my iPad2 gave accurate altitude data on my plane trip to Vegas last weekend. The Foreflight App for pilots was within 200 feet of accuracy on the trip, which is much better than my old Garmin unit, which was accurate to around 500 feet. Having dedicated GPS apps has made my plane and auto trips enjoyable, without having to worry about cell tower or wifi coverage.
Comments
Again from my quick start guide: you will typically have anywhere from 5 -10 satellites.
The article says that eight are visible in the current system. So that must be the max.
Thanks, but I also own TomTom. I haven’t opted for in-app traffic data. It’s not something I experience often, for which I’m very happy.
I also use Navigon (and will use Navigon Europe on my trip next month). I also did not opt for the extra fee for traffic "info", for the same reasons, and I've heard it's not quite ready for prime time. Not sure where TomTom and Navigon get their traffic data, but I know many companies are working (and Apple also, as announced) on a better way to gauge traffic. If it were really accurate, gathering speed and location info on thousands of cars, then I would feel it would really be useful for urban commuters, since you can only have so many Eye In The Sky helicopters, or people analyzing cams around the city, to be that confident that if you choose a different route to work/school, etc, you will really save time, gas, and hassle.
Ok. So according to the Wikipedia article, my numbers are correct. While it prefers four, it can use three for a quick and dirty fix, and it can use more for redundant information. And as eight are visible at one time, it can use up to eight.
The only thong about the article that's not quite correct is the current accuracy. It's much more accurate than 65 feet.
If the number of discovered satellites drops to fewer than 4 you will lose gps fix. At least four are required to maintain positional estimates.
Any app that you permit to access your location can create its own database (remember, receiving location information is one of the permitted background activities). However, the app would not start tracking after a restart of the iPhone until you start the app for the first time (there are no login items in iOS).
We need to know whether these apps are allowed to keep any of this info. I tend to doubt it, as they have to ask each time. I don't remember any app stating that they were keeping any of the info, except for mapping apps such as my GPS app. And we're expressly telling them to do so each time.
I think people just assume it?s three satellites for GPS because of the association with triangulation, even though it?s multiple triangles that all confer using a network of triangles.
Many units include status indicators showing satellites detected and satellites locked..
That is how my Garmin works. I see each satellite as it is detected and slowly locked. As soon as I have three it displays my location on the map. This experience along with the documentation included with the device lead be to believe that only three satellites were required. I did notice that it sometimes would display the elevation incorrectly. I first noticed this when descending a steep route to sea level. Now I understand that it must be reusing my last known elevation in lieu of a fourth satellite.
I also use Navigon (and will use Navigon Europe on my trip next month). I also did not opt for the extra fee for traffic "info", for the same reasons, and I've heard it's not quite ready for prime time. Not sure where TomTom and Navigon get their traffic data, but I know many companies are working (and Apple also, as announced) on a better way to gauge traffic. If it were really accurate, gathering speed and location info on thousands of cars, then I would feel it would really be useful for urban commuters, since you can only have so many Eye In The Sky helicopters, or people analyzing cams around the city, to be that confident that if you choose a different route to work/school, etc, that you will really save time/gas/hassle.
Even when you have accurate flow data, if there's a delay of even 5 minutes in delivering that info to your mobile device, the traffic data may no longer be reliable, depending on the cause of the reported traffic issues.
Yes, once position has been established, then it's "the more the merrier" for accuracy, but on a declining scale. Once you've got 6 or 7 sats identified, adding another two or three more doesn't improve the accuracy all that much. Perhaps from an estimated 12' down to 9-10'. But the accuracy of the gps location isn't the big variable. It's the quality of the maps the device uses. All maps used by consumer gps devices are rift with positional errors.
As for how many satellites are generally used for navigation, it's common for 8-11 satellites to be "found" by modern gps navigation devices within a few minutes at most.
This is what I've been saying, and you've been telling me no to. Though, as only eight satellites are line of horizon at any one time, I wonder how the receiver sees more than that number.
If the number of discovered satellites drops to fewer than 4 you will lose gps fix. At least four are required to maintain positional estimates.
I assume that's only if you're moving though. Theres too much evidence that shows that only three will locate you accurately, at least to horizontal position without elevation data. As the article shows, the assumption is that you are on the earth's surface if you are below 11 miles.
Straight, to-the-point mea culpa. I say this as someone who was vehemently demanding something like this (despite having taken much abuse from this forum).
All is forgiven!
In all fairness the “abuse," which I recall was simply disagreeing with you, wasn’t against you requesting Apple respond to the issue or making the changes they said they would make on these bugs — which I would qualify more as parochial coding not a bug — but with other aspects of your hypothesis.
I wish I understood better why GPS needs a WiFi hotspot database to be speedy. GPS originally was for military applications right? Missile tracking and such. Surely such a system does not take, as Apple claims, "several minutes" to return a result?
Aren't those satellites constantly broadcasting - surely you just need to listen for a second or two? Or was the system built with the assumption that the thing you are locating is high and fast moving?
Once a device has acquired its location and it remains in contact with the satellites, location updates are very fast. All military equipment simply will stay connected constantly (except submarines that is).
As far as I remember assisted-GPS provides you with the precise position of the satellites your GPS device is communicating with (and indirectly thus which of the satellites are ones that should be communicated with because they are in best position). The data connection to the satellites is fairly slow (hey it is a pretty old system), the main data sent from the satellites is very precise time signals, as the travel time of the signal depends on the distance between you and each satellite, you can from the travel time and the position of the satellites calculate your position. The satellites also send their position but receiving that takes longer than the pure time signal.
A friendly, active and patient forum with exceptional knowledgeable members and moderators. There's already been too many wrong assumptions posted in this thread to take up more time from the original subject.
To MStone: Watch more closely the next time your gps boots up. You won't have a lock at three satellites. They lock in so quickly it's sometimes hard to catch. If the sat bar is solid it's locked. If hollow it's only found but not yet usable for navigation purposes.
To Mel: The article you're relying on is incorrect on several statements. Wander on over to GPSReview,net one day when you have time.
But if they're broadcasting it, how can they stop anyone who wants looking at it?
Encryption, there is an additional encrypted signal that contains more information which increases accuracy. The military has the key to decrypt it, you don't have it.
Mbarriault, you read Engadget comments? And still well enough to post here? Commendable!!
I've warned before not to read the comments in Engadget articles. They have the worst name-calling, immature and angry posters on the web IMHO.
Wasn't it Engadget which had switched off their comments for a month, because they were getting so ridiculous?
Now that we are told the phone keeps the information for over a year, they are going to turn it off?
Too bad. I got a kick out of seeing where I had been, and like photos, and a journal, helped me remember things I had forgotten.
Sounds like a great app we could install that would maintain a history for us.
I'd think that it would be fairly simple to write an app that people could voluntarily use to do precisely what you're suggesting. The trick would be writing it such that it didn't become a battery drain.
Opportunity!
Only if what you are admitting is true an not hiding a bigger lie.
Tin foil hat, anyone?
We need to know whether these apps are allowed to keep any of this info. I tend to doubt it, as they have to ask each time. I don't remember any app stating that they were keeping any of the info, except for mapping apps such as my GPS app. And we're expressly telling them to do so each time.
Yes, they will explicitly ask you every time you start them up. But Apple cannot tell apps to 'forget' any data, it can only reject apps that store data but do not make that clear to the user.
Agree completely, though I think it's a fairly seamless transition from SNL to the US Senate. (The Senate's funnier of course.) Too bad we never did get a Senator Blutarsky.
Calmer minds have noted that Franken's questions are totally appropriate from the viewpoint of the non geek world (i.e. most people.)
If this episode sheds light on the 24-hour homing device that most of us carry around, then its a good thing. People need to be conscious of the implications of technology... most aren't.
I'd like to see people also be reminded that the FastPass on their dash tracks them even more closely.
There's no conspiracy theory, it's just obvious that Google is lying because their "inadvertent" excuse isn't credible when you consider they had to be seeing all the private data they collected go into their database for years.
There is absolutely no similarity between these issues.
Yup....There is a huge difference.
These are locally stored files (on your computer) which after the bug causing the data to be saved for 1 year, uptil 7 years, would probably have increased in size by a few mb. Its the same data, just that the automatic cache flushing algorithm was wrong.
OTOH, Google was picking up data that was completely irrelevant, and they didn't need in the first place. They specifically had to write code for it, it being something they didn't need, and collecting of which is illegal.
That is how my Garmin works. I see each satellite as it is detected and slowly locked. As soon as I have three it displays my location on the map. This experience along with the documentation included with the device lead be to believe that only three satellites were required. I did notice that it sometimes would display the elevation incorrectly. I first noticed this when descending a steep route to sea level. Now I understand that it must be reusing my last known elevation in lieu of a fourth satellite.
I’m still and will likely always be amazed that we have the technology in our lifetime to get such accurate data.
(Apologies to JeffDM for all these FIRST posts)