Can someone answer how does the screenshot works? irrespective of mobile phone or PC? I've tried to look for the answer all over the internet but every where i can find only the videos how to take screenshot? But none of them gives me the result. Does that relates to software which buffers and converts the screen-content to image?
Irrespective of hardware or software in computers or smartphones, there is something called a "frame buffer" that stores all of the pixels currently displayed on the screen as numbers. A screenshot is essentially a dump of all of those numbers into a file, with more numbers tacked on the front to cause a computer to interpret them as a particular type of image.
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It's already a long story... I bought my phone sometime in 2013, and found that it's GPS doesn't work, just after the warranty expired. I tired everything to get it function properly without any success, and finally gave up. Up until now I could live without it, but right now I'm really in need of this functionality, and only because of that I'd have to buy a new smartphone now if it can't be fixed.
Here's the issue: I turn on GPS positioning in the OS, and open up some GPS tester application, and this is what happens: After a couple of seconds, it finds the first satellite, and in 1-2 minutes I already have 6-7 or even 8 of them. - So it seems the hardware is OK, the receiver works. But after that, I cannot get a GPS fix. I can wait 10-20-30 minutes, or even waited for an hour...Nothing happens. No position fix, GPS useless. I've tried 10+ GPS apps, the result is always the same. They see the satellites, but never establish a position fix.
What I've done so far: I read on xda-developers that this phone for some reason doesn't have a gps.conf file in system/etc which could cause the problem, so I downloaded one for my country, rooted my phone and pasted it to that folder. Nothing changed. I'm out of ideas, and there's nothing more I could find on the internet. Any ideas here? Or should I get a new phone? It's really annoying because it seems it's not a hardware issue, so it should be able to be fixed somehow...
Btw that's the content of my gps.conf file in system/etc for Austria, the country I live in:
NTP_SERVER=at.pool.ntp.org
XTRA_SERVER_1=http://xtra1.gpsonextra.net/
xtra.bin
XTRA_SERVER_2=http://xtra2.gpsonextra.net/
xtra.bin
XTRA_SERVER_3=http://xtra3.gpsonextra.net/
xtra.bin
SUPL_HOST=supl.google.com
SUPL_PORT=7276
(I have no idea what it's for.)
Unassisted GPS in a GPS module which has never been turned on, or has to find a new position solution, can actually 2-4 hours at worse. Adding to this, a single processor Android smart phone such as yours likely throttles severely, and is not likely to schedule much resource for non-essential routines.
Be sure to turn on 'Google Location Services' to enable assisted GPS for a faster position solution. If any factory setting has a toggle for location- assistance, make sure it is enabled. Be sure to move away from buildings so the sensors view of the sky is widest.
I've been using some popular taxi-hailing apps like Uber and OLA in India and the same, Uber, in USA. The location of cars, where they're moving and my position on the app's map are always off. So much so, I'd need to call the driver to tell them where I'm at. From this Quora thread I was able to narrow the problem to be in use of Maps API or GPS signals.
The Quora post: https://www.quora.com/Why-is-GPS-in-India-so-inaccurate
The parody video: https://www.youtube.com/watch?v=hjBM-zSq3NU
It is possible that the problem is caused by your device or the capability of GPS in your area. newer phones can use 10's of GPS's to locate themselves this is actually called AGPS. However, older phones use three cell towers (not GPS) in order to triangulate your position. While, this method was fairly accurate it was known to be more than a couple of feet off on occasion. Even older phones, may even use only two cell towers, the problem here that the speed at which this data (light speed) allowed for a very large margin of error which could be your problem. Also, some phones without AGPS use only one GPS to locate, and this may also complicate things for you.
I need to read GPS coordinates using a VB.NET program directly from a GPS device connected to the computer via USB (bluetooth also OK but prefer USB). My constraints are:
The computer running the software is NOT connected to the internet. It is a stand-alone machine in a moving vehicle.
I need to be able to read GPS coordinates from the device while the vehicle moves and use the device to perform location-aware queries on a local database
The GPS device can be anything (e.g. Garmin GPS or GPS card without display), as long at it can be purchased off the shelf or over the internet.
The user group for this solution is quite small (about 40 users).
I have already checked out GPSGate (http://gpsgate.com/) and emailed my requirements to them. They replied, and I quote: "I am sorry but we have no product for you." (end of reply).
I also checked out Eye4Software) and tried using their demo product but it does not pick up my Garmin Nuvi via USB. They responded to my questions but unfortunately their OEM product is an ActiveX dll and I am looking for a .NET based solution.
So if anyone has a "home-grown" solution based on the .NET framework, that can be easily duplicated, I would really appreciate it. Many thanks!
Most of the USB GPS pucks will speak a standardized protocol called NMEA 0183. There are several .net protocols out there that decode this protocol, see here for some pointers to get started.
So, if when shopping around you just check that the device is able to generate NMEA you should be up and running in a minimum of time, and at a reasonable cost.
EDIT: a "gps puck" is a GPS receiver shaped more or less like a hockey puck, like this one
For in-car use there are specific versions that can be fixed onto the vehicle's roof
They are pretty common (many online shops carry them) but select them based on the chip that's inside, the popular Sirf Star 3 is still a solid performer, stable and accurate. I haven't had the chance to play with its successor, the Sirf Star 4 yet, and I'm not implying these are the only good chips around, only that I got most experience with this chip.
AR browsers include those like wikitude, Layar etc that are available for Iphone and Android smartphones .
When you point your camera to a landmark they automatically overlay previously available information for a location over it (e.g. name of a restaurant over its door)
If the accuracy of GPS as states by some is ~ 10 m , how can this be done accurately ?
I mean if they track the location of your phone to display geographically accurate information , a difference of even 2-3 m can cause havoc.
you can check by yourself in the code of mixare, which is an augmented reality browser released under a free software license (GPLv3). The source code is available on github both for android and iPhone.
To answer your question: there are errors, mostly because of the compass readings (digital compasses are unreliable because they pick up every kind of noise). What helps is that you are usually looking to objects that are quite big (buildings etc.) hence the error is not THAT visible to the end user, but it's still there, trust me :)
HTH
Daniele
Disclosure: I am the project leader of mixare and main developer of the android version
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I assume it doesn't connect to anything (other than the satelite I guess), is this right? Or it does and has some kind of charge?
GPS, the Global Positioning System run by the United States Military, is free for civilian use, though the reality is that we're paying for it with tax dollars.
However, GPS on cell phones is a bit more murky. In general, it won't cost you anything to turn on the GPS in your cell phone, but when you get a location it usually involves the cell phone company in order to get it quickly with little signal, as well as get a location when the satellites aren't visible (since the gov't requires a fix even if the satellites aren't visible for emergency 911 purposes). It uses up some cellular bandwidth. This also means that for phones without a regular GPS receiver, you cannot use the GPS at all if you don't have cell phone service.
For this reason most cell phone companies have the GPS in the phone turned off except for emergency calls and for services they sell you (such as directions).
This particular kind of GPS is called assisted GPS (AGPS), and there are several levels of assistance used.
GPS
A normal GPS receiver listens to a particular frequency for radio signals. Satellites send time coded messages at this frequency. Each satellite has an atomic clock, and sends the current exact time as well.
The GPS receiver figures out which satellites it can hear, and then starts gathering those messages. The messages include time, current satellite positions, and a few other bits of information. The message stream is slow - this is to save power, and also because all the satellites transmit on the same frequency and they're easier to pick out if they go slow. Because of this, and the amount of information needed to operate well, it can take 30-60 seconds to get a location on a regular GPS.
When it knows the position and time code of at least 3 satellites, a GPS receiver can assume it's on the earth's surface and get a good reading. 4 satellites are needed if you aren't on the ground and you want altitude as well.
AGPS
As you saw above, it can take a long time to get a position fix with a normal GPS. There are ways to speed this up, but unless you're carrying an atomic clock with you all the time, or leave the GPS on all the time, then there's always going to be a delay of between 5-60 seconds before you get a location.
In order to save cost, most cell phones share the GPS receiver components with the cellular components, and you can't get a fix and talk at the same time. People don't like that (especially when there's an emergency) so the lowest form of GPS does the following:
Get some information from the cell phone company to feed to the GPS receiver - some of this is gross positioning information based on what cellular towers can 'hear' your phone, so by this time they already phone your location to within a city block or so.
Switch from cellular to GPS receiver for 0.1 second (or some small, practically unoticable period of time) and collect the raw GPS data (no processing on the phone).
Switch back to the phone mode, and send the raw data to the phone company
The phone company processes that data (acts as an offline GPS receiver) and send the location back to your phone.
This saves a lot of money on the phone design, but it has a heavy load on cellular bandwidth, and with a lot of requests coming it requires a lot of fast servers. Still, overall it can be cheaper and faster to implement. They are reluctant, however, to release GPS based features on these phones due to this load - so you won't see turn by turn navigation here.
More recent designs include a full GPS chip. They still get data from the phone company - such as current location based on tower positioning, and current satellite locations - this provides sub 1 second fix times. This information is only needed once, and the GPS can keep track of everything after that with very little power. If the cellular network is unavailable, then they can still get a fix after awhile. If the GPS satellites aren't visible to the receiver, then they can still get a rough fix from the cellular towers.
But to completely answer your question - it's as free as the phone company lets it be, and so far they do not charge for it at all. I doubt that's going to change in the future. In the higher end phones with a full GPS receiver you may even be able to load your own software and access it, such as with mologogo on a motorola iDen phone - the J2ME development kit is free, and the phone is only $40 (prepaid phone with $5 credit). Unlimited internet is about $10 a month, so for $40 to start and $10 a month you can get an internet tracking system. (Prices circa August 2008)
It's only going to get cheaper and more full featured from here on out...
Re: Google maps and such
Yes, Google maps and all other cell phone mapping systems require a data connection of some sort at varying times during usage. When you move far enough in one direction, for instance, it'll request new tiles from its server. Your average phone doesn't have enough storage to hold a map of the US, nor the processor power to render it nicely. iPhone would be able to if you wanted to use the storage space up with maps, but given that most iPhones have a full time unlimited data plan most users would rather use that space for other things.
There's 3 satellites at least that you must be able to receive from of the 24-32 out there, and they each broadcast a time from a synchronized atomic clock. The differences in those times that you receive at any one time tell you how long the broadcast took to reach you, and thus where you are in relation to the satellites. So, it sort of reads from something, but it doesn't connect to that thing. Note that this doesn't tell you your orientation, many GPSes fake that (and speed) by interpolating data points.
If you don't count the cost of the receiver, it's a free service. Apparently there's higher resolution services out there that are restricted to military use. Those are likely a fixed cost for a license to decrypt the signals along with a confidentiality agreement.
Now your device may support GPS tracking, in which case it might communicate, say via GPRS, to a database which will store the location the device has found itself to be at, so that multiple devices may be tracked. That would require some kind of connection.
Maps are either stored on the device or received over a connection. Navigation is computed based on those maps' databases. These likely are a licensed item with a cost associated, though if you use a service like Google Maps they have the license with NAVTEQ and others.