Moved: A-GPS on Sony Ericsson Xperia X1i

[yaozer]

Gang,

I've just started using Garmin Mobile XT on my new phone recently, it really works smoothly together with the great standard map I got from this forum. I am really surprised it's working so well considering it is more of a phone than a GPS. I've researched on A-GPS on the net, and found out that assisted GPS uses some network carrier data to function. I tried looking for discussions on GPS with the Xperia, but found none (except for a YouTube entry). I've read that Nokia N95 users see their phones connecting to GPRS or HSDPA in order to get these necessary data. But with the Xperia and Garmin, I don't see my phone connecting to any of these services (GPRS, EDGE, UMTS, HSDPA, etc.) but it could still find where I am. I tried to check on my Globe unbilled items via 2312 but it only showed me my voice calls and SMS totals. I was curious to know whether I've incurred some data charges but it didn't show.

So question 1 is, do you think the N95 connects to data services because it uses Google Maps, and that if it uses Garmin it doesn't need to connect to data services anymore? I'm not really sure what type of A-GPS the Xperia has (I've read that there are 4 types), I hope it is the Standalone type.

Question 2, if the phone doesn't show it is connecting/connected to data services, does that mean it it is IMPOSSIBLE for it to download data? Or can it do it in the background?

Thanks for your time.

[Jan]

garmin mobilext does not connect to data services.
as far as i know (I MIGHT BE WRONG HERE) the agps only uses cell tower triangulation and so far globe is not charging for that yet. yet of course being the magic word.
if you are not sure, switch of the assisted part and just use the gps.

HTH

[yaozer]

Thanks Jan for that info. I just can't believe this little gadget can do almost anything! Anyway, I'll try to observe further.

Now I need to study how to use Mapsource so I can suggest some corrections.

[amf]

If I may contribute:

A-GPS equipped devices does not connect to your network to download data (so no data charging). It said to be more accurate because as Jan stated it also uses cell towers to triangulate your position aside from the GPS signals. I have not used Mobile XT but my iPhone can locate me inside the house with GPS turned on and EDGE/3G off.

It will only connect and download data (and you get charged) if and when it needs viewing online maps like Google Maps. If the map is located in the phone, no data is retrieved from your network.

You can try turning off GPRS/EDGE/3G (to make sure that no data is being retrieved from the network) and then navigate and see what happens.

Incidentally, I moved this thread from the "PUB" to "Smartphones or PDA"

Thanks.

allan

[yaozer]

Thanks amf, that clears up a lot of doubts. I believe the N95 forum that I visited recently only had Google Maps as its GPS software, I'm not sure if Garmin Mobile XT is available for Symbian users.

The first time I tried Google Maps, it didn't connect to any of the data services. Then I noticed a little while later that it wasn't getting a lock on me. So I tried the QuickGPS software that came with the phone (connected via WiFi), it downloaded some stuff off the internet and closed down. Then I fired up Google Maps and it started attempting to connect via GPRS, downloaded some 10kb worth of data, paused and never finished, so I cancelled it. Maybe it was actually trying to download map details instead huh?

Great forum! I'll continue to study Mapsource

[amf]

No prob yaozer!

I guess QuickGPS is quite similar to Garmin's Hotfix feature. It downloads ephemeris data ahead of time so that the next time the GPS is used (especially during cold starts), one can get a faster lock as the GPS chip knows where the sats are and at what channels. I understand that the data is provided by the US DoD.

QuickGPS uses wifi or GPRS/EDGE/3G though (you get charged by your network provider) while Hotfix gets the data from the orbiting sats themselves.

I'd say you use or launch QuickGPS every time you're connected to a wifi network so it's free and you always have fresh data.

As for Mapsource, I'm a noob too and it will not take you much time to get the hang of it.

Cheers.

allan

[deadman9119604]

Garmin MobileXT

Where can I get the Garmin MobileXT?

[amf]

Where can I get the Garmin MobileXT?

Welcome!

You need to buy it from Garmin.

allan

[SilentRiver]

This might help you out guys...

http://www.zenyee.com/2008/04/19/agp...-myth-or-fact/

and this one also

Source: http://www.htc.com/asia/faqs.aspx?p_...at=66&id=51822
Qn: What is AGPS? How is it different from External GPS and QuickGPS?
Ans: AGPS (Assisted Global Positioning System) is a technology that helps reduce the time to determine a location by connecting to an assistance server. With conventional GPS systems, it is often difficult to provide reliable positions under poor signal conditions, for example, if you are surrounded by tall buildings (as a result of multipath) or if the satellite signals are weakened when you are indoors. The AGPS system, consisting of an integrated GPS receiver and network components, boosts performance beyond that of the same receiver in a stand-alone mode. AGPS will use your device's data connection (i.e. GPRS/3G) to connect to the assistance server and this may incur additional connection fees. QuickGPS is a device application that can speed up the time for determining your GPS position by downloading the latest satellite data through your device's connection (i.e. Internet, ActiveSync, or data connection.)

[rem]

I have been using Garmin XT on a PDA phone for quite some time now. A-GPS will incur you data charges so be aware of that.

Garmin XT will SOMETIMES automatically connect to data services upon opening the software. You will know that this is connecting to the data server when you see a connection at the signal bar on the upper right hand corner of your screen (it depends on where you are and what data signals are available e.g. 3G+ for hsdpa, 3G for 3G, E for edge, and G for GPRS)

The software does this to update itself on its location and when it is having a hard time to acquire signals (like when you transfer to a different location which is kilometers away from your last 3D signal) or when you barely use XT and the unit needs a "cold" connection from satellites above.

There would have been no problem if the PocketPC phone disconnects itself automatically from the internet upon triangulating the location. However you will notice that once it connects to the data network, you will have to disconnect it manually.

What you can do is:
1) Whenever you have access to a wifi connection, open up your XT and it will update its location using data signal from the wifi.
2) Mobile internet now is cheap. I don't know with Smart but with Globe just turn on the time based internet and they will charge you Php5 per 15minutes.

As per experience, there is no definitive guideline as when XT will connect to mobile internet. So you just have to be aware of the symbols at the taskbar of your phone.

Goodluck!

rem

[amf]

Oh...

My iPhone 3G's A-GPS chip may be faulty as even if WiFi/3G/Edge/GPRS is disabled, it can accurately find and lock on my position and log my tracks too.

[rem]

A-GPS as the name implies only assists your GPS receiver to get signals from satellites faster than regular process relying only on your GPS antenna.

What A-GPS does is use triangulation from cellular sites instead of getting signals from satellites right away. This means that the receiver has a rough idea where you are at that moment. Upon getting that rough estimate of your location it will then know what satellites should be hovering above and will easily lock on these signals. These happens during "cold starts" like what i said in the previous comment.

So even if you turn off your data connection in your 3G iphone it can and will still be able to give you accurate readings of your position.

Just imagine older models of GPS receivers without A-GPS, you really have to wait sometimes for minutes just to lock on the signal.

HTH.

[amf]

If you read my post in the first page, that's almost exactly what I said.

And my Nuvi (SirfIII, non-AGPS) locks on sats as fast and sometimes faster than my AGPS-equipped iPhone.

[rem]

allan my reply on blue text

[QUOTE=amf;313]If I may contribute:

A-GPS equipped devices does not connect to your network to download data (so no data charging). It said to be more accurate because as Jan stated it also uses cell towers to triangulate your position aside from the GPS signals. I have not used Mobile XT but my iPhone can locate me inside the house with GPS turned on and EDGE/3G off.

As per experience, A-GPS connects to your network and downloads data which is needed to triangulate your location using cellular sites for faster connection to satellite signals. Data charges will be incurred with this process. It is not MORE accurate with ordinary GPS, it only facilitates to make you lock on satellite signals faster.

A few years ago, there is such a thing as SA or Selective Availability which makes your gps locations only at least 30m accurate. This makes commercial gps receivers inaccurate for public use so as to differentiate it from military grade gps receivers. In 1998, US President Clinton made a directive to turn off SA thus making commercial gps receivers accurate up to 3m depending on the availability of satellites and other external factors.

With google map installed on iphone, Google increased their coverage using triangulation thus making it more accurate up to a certain radius. If you noticed before, you get a bigger blue radius when pressing the "My Location" button but these days it locates you with a certain level of accuracy.

Accuracy and faster lock on time to satellites depends on different factors such as A-GPS, surrounding buildings, cold versus hot starts (as previously explained), clear sky, gps chipsets (sirfIII versus no sirf), and others



It will only connect and download data (and you get charged) if and when it needs viewing<textarea name="message" id="vB_Editor_001_textarea" rows="10" cols="60" style="display:block; width:540px; height:250px" tabindex="1" dir="ltr">

If I may contribute:

A-GPS equipped devices does not connect to your network to download data (so no data charging). It said to be more accurate because as Jan stated it also uses cell towers to triangulate your position aside from the GPS signals. I have not used Mobile XT but my iPhone can locate me inside the house with GPS turned on and EDGE/3G off.

It will only connect and download data (and you get charged) if and when it needs viewing online maps like Google Maps. If the map is located in the phone, no data is retrieved from your network.

You can try turning off GPRS/EDGE/3G (to make sure that no data is being retrieved from the network) and then navigate and see what happens.

Incidentally, I moved this thread from the "PUB" to "Smartphones or PDA"

Thanks.

allan

just for clarification

[amf]

A-GPS as the name implies only assists your GPS receiver to get signals from satellites faster than regular process relying only on your GPS antenna.

What A-GPS does is use triangulation from cellular sites instead of getting signals from satellites right away. This means that the receiver has a rough idea where you are at that moment. Upon getting that rough estimate of your location it will then know what satellites should be hovering above and will easily lock on these signals. These happens during "cold starts" like what i said in the previous comment.

So even if you turn off your data connection in your 3G iphone it can and will still be able to give you accurate readings of your position.

Just imagine older models of GPS receivers without A-GPS, you really have to wait sometimes for minutes just to lock on the signal.

HTH.

My posts #4 and #6:

If I may contribute:

A-GPS equipped devices does not connect to your network to download data (so no data charging). It said to be more accurate because as Jan stated it also uses cell towers to triangulate your position aside from the GPS signals. I have not used Mobile XT but my iPhone can locate me inside the house with GPS turned on and EDGE/3G off.

It will only connect and download data (and you get charged) if and when it needs viewing online maps like Google Maps. If the map is located in the phone, no data is retrieved from your network.

You can try turning off GPRS/EDGE/3G (to make sure that no data is being retrieved from the network) and then navigate and see what happens.

Incidentally, I moved this thread from the "PUB" to "Smartphones or PDA"

I guess QuickGPS is quite similar to Garmin's Hotfix feature. It downloads ephemeris data ahead of time so that the next time the GPS is used (especially during cold starts), one can get a faster lock as the GPS chip knows where the sats are and at what channels. I understand that the data is provided by the US DoD.

QuickGPS uses wifi or GPRS/EDGE/3G though (you get charged by your network provider) while Hotfix gets the data from the orbiting sats themselves.

I'd say you use or launch QuickGPS every time you're connected to a wifi network so it's free and you always have fresh data.

I guess except for the the data downloading part, it's similar.

And about the data downloading and getting charged using AGPS per se, I still maintain that AGPS alone does not connect and download data when activated (download data in the sense that one incurs charges on one's phone bill). It is the application or software that uses AGPS that tries to connect and download data. Unless MS and Apple have different inplementation of AGPS.

Oh and BTW, I don't use Google maps in my iPhone.