How does GPS work if no satellites?

any danger of telling us the make and model of phone yet?

It's a ZTE Z796C.  I hope there is a point to you asking for my personal information. 

um.. .what's personal about the type of phone you have?

We didnt ask you for your DNA sequence, or your bank account number...  .....     .........................

Soooooooooooooooooooooooooo.. whats your bank account number...?

Only kidding..... I'll hack it later! bwahahaha!

It's a ZTE Z796C.  I hope there is a point to you asking for my personal information.

well its pretty basic info to request the model of the instrument which is at the center of your argument to be able to tell your altitude without gps. Although you then went on to show there is no consistency when you tried at different locations. I would be surprised if you were using an iphone or sony or other tried and tested phone. I have never heard of a zte majesty is that a common phone where you live?

It's a ZTE Z796C.  I hope there is a point to you asking for my personal information.

The reason you're getting varying altitude numbers is that the phone does not have GPS... it's estimating your altitude using triangulation - which as you can see now, is rather pointless.

That is not correct.  Unless there is something I am not understanding, there is a GPS feature on the phone that I can enable or disable, just like wifi and bluetooth. 

That is not correct.  Unless there is something I am not understanding, there is a GPS feature on the phone that I can enable or disable, just like wifi and bluetooth.

i would be interested in seeing a side by side comparison with a name brand high end model say an iphone or samsung. I cant find any reviews on the gps function on your phone as i cant find any reviews at all really. Thanks for offering up the info though.

That is not correct.  Unless there is something I am not understanding, there is a GPS feature on the phone that I can enable or disable, just like wifi and bluetooth.

I was just going on the specs - no mention of GPS..

http://www.smartphonezero.com/zte-z796c-majesty-specs/

Some phones use pseudo - they have a 'gps' function but really its just network triangulation... it might be that? I have no idea though in reality.

I've done more reading.. I've found different specs on your phone that says that it does have GPS.. so there you go..

However, Altitude will be very inaccurate in the city around structures.

In fact, GPS Alt is not the most accurate measurement in the first place, in the order of 10 to 25 metres vertically.   Good ones will get you to within 1 metre on the ground (Long/Lat).. generally for altitude you'd use an altimeter (Baromoter) - that will give you an exact number as long as you enter in the correct reference pressure for the area you're in..

It looks like your phone is one of those el cheapo's you get in the cigarette section of the supermarket.. (no offence!).. so I wouldnt expect it to give you much.

My iPhone never ceases to amaze me on how accurate it is...

If we get back to the original argument, to get a 3D reference on a GPS, it MUST have at least 4 sat's connected... for Altitude (albeit not that accurate) the 4th satellite must be high.. as in.. in space.  ground based system will only give you an inaccurate 2D reference.

Just found this.. thought it was pertinent..

http://www.extremetech.com/extreme/126843-think-gps-is-cool-ips-will-blow-your-mind

looks like your phone is one of those el cheapo's you get in the cigarette section of the supermarket.. (no offence!).. so I wouldnt expect it to give you much.

My iPhone never ceases to amaze me on how accurate it is...

thanks I didnt want to be the one to say that!

Another intersting find.. seems a ground based GPS system has been developed - it has more accurate reference and can give you your altitude to 2 inches!

http://www.locata.com/technology/locata-tech-explained/

Current the best ground based tech available, and very very new.

Another intersting find.. seems a ground based GPS system has been developed - it has more accurate reference and can give you your altitude to 2 inches!

http://www.locata.com/technology/locata-tech-explained/

Current the best ground based tech available, and very very new.

interesting read - good find

You still have not explained how the altitude is displayed on my phone with more consistency without GPS than with it. 

You still have not explained how the altitude is displayed on my phone with more consistency without GPS than with it.

Because altitude, however inaccurate due to the quality of your phone's sensors, is being calculated on the fly. When it is being displayed when GPS is turned off it is simply getting the information from a database.

You still have not explained how the altitude is displayed on my phone with more consistency without GPS than with it.

both gps and cell readings you gave are consistently inconsistent. Dare I suggest a budget phone gives budget performance? what app are you using?

You still have not explained how the altitude is displayed on my phone with more consistency without GPS than with it.

Well, what is your hypothesis?  We haven't actually got access to your phone.

Well, considering that everyone is saying that you can only get altitude readings with Satellites, I suppose that I would have to conclude that I have a satellite phone. 

Well, considering that everyone is saying that you can only get altitude readings with Satellites, I suppose that I would have to conclude that I have a satellite phone. 

An altitude derived from a database is not an altitude reading, at least not in the way we are discussing it here. We are talking about using an instrument (such as a phone) that calculate's the altitude. A calculation is not the same as pulling info from a database.

Well, considering that everyone is saying that you can only get altitude readings with Satellites, I suppose that I would have to conclude that I have a satellite phone. 

Whst app are you using for altitude?

Clearly GPS uses orbiting satellites, as shown on an app or satnav or professional receivers in aircraft or used for surveying.

Many mapping apps, including iPhons's Apple Map, use a mapping database that includes terrain topography.   If the phone can find your location then it will know the elevation too.  No need for satellite reception for this as the phone can, and does, triangulates position using nearby cell towers.  This is how your phone knows your elevation with GPS disabled.  If you left the GPS disabled and lifted off in a hot air balloon your elevation would not change. 

Now, take your phone away from cell phone reception and disable the GPS and you will have no idea what your elevation is. 

Try this:  GPS reception is weak inside an airliner...especially away from windows...and there is no cell phone recaption at altitude so next time you're on a plane disable the GPS then check out your position and elevation.  Does the elevation say 35,000'?  I think not.  It won''t know where you are either.  Now turn on the GPS and place the phone next to the window.  Your mapping feature likely will not work because it relies on cell reception to download maps but the phone will show an accurate lat/long and will show your actual altitude.

You do not have a satellite phone...this is how all smart phones work.

I don't flat out disregard what you are saying.  However, I just find it odd that when I went up 30 ft., the GPS altitude went down 10 ft., while the non-GPS altitude went up 4 ft.

I don't flat out disregard what you are saying.  However, I just find it odd that when I went up 30 ft., the GPS altitude went down 10 ft., while the non-GPS altitude went up 4 ft.

just one of many inconsistencies with your litte experiment but hold onto that if it makes your feel better

I don't flat out disregard what you are saying.  However, I just find it odd that when I went up 30 ft., the GPS altitude went down 10 ft., while the non-GPS altitude went up 4 ft.

That may be so but GPS is designed to be used outdoors and clear of obstructions such as buildings and tress.  Your GPS signals come from satellites so best if they can "see" you.  Even when outdoors on a city street surrounded by tall buildings it's common to lose the GPS signal due to interference.

You might still get a GPS signal indoors but it will be weak and full of errors....hence the results of your 30' climb.  Cell phone tower triangulation is pretty good at calculating your position but not as good as GPS (when outdoors) and will have errors too...particularly in the vertical because, remember, it's using a mapping database to find your elevation and if the calculated position is slightly off so will be your elevation.  Also, your experiment sample scale is far too small using your relatively basic instruments.  Try it again by climbing a tall tower.

Incidentally, did you know GPS, SatPhone and Sat-TV antennas are always mounted on the TOP of the airplane so there is no interference between the transmitter and receiver?  If GPS is a Ground Based system as FEers suggest wouldn't it be better to mount the GPS antenna on the belly of the plane as is done with antenna that use ground based radio and navigation systems?

I don't flat out disregard what you are saying.  However, I just find it odd that when I went up 30 ft., the GPS altitude went down 10 ft., while the non-GPS altitude went up 4 ft.

It might also be that your phone has a crappy GPS.

Dedicated GPS units (I have one for hiking) thrash phones in terms of performance, especially for altitude.  Though my iPhone does a pretty good job.

I do have a dedicated GPS unit.  However, I use my phone most of the time for convenience; especially because it allows me to easily download Geochache information, where as my dedicated GPS does not. 

One of these days, I will need to do a side by side comparison between the dedicated unit and my phone. 

I do have a dedicated GPS unit.  However, I use my phone most of the time for convenience; especially because it allows me to easily download Geochache information, where as my dedicated GPS does not. 

One of these days, I will need to do a side by side comparison between the dedicated unit and my phone.

I've done a bit of that hiking in places like Scotland - the iPhone is pretty good - bang on most of the time in terms of longitude and latitude, but sometimes seems confused over altitude (which is much less important when walking).

Quote from: jroa on February 16, 2014, 12:18:44 PM

I do have a dedicated GPS unit.  However, I use my phone most of the time for convenience; especially because it allows me to easily download Geochache information, where as my dedicated GPS does not. 

One of these days, I will need to do a side by side comparison between the dedicated unit and my phone.

I've done a bit of that hiking in places like Scotland - the iPhone is pretty good - bang on most of the time in terms of longitude and latitude, but sometimes seems confused over altitude (which is much less important when walking).

Well, I have a cheap smart phone and it is the same way, so I feel a little better now. 

You still have not explained how the altitude is displayed on my phone with more consistency without GPS than with it.

Yeah i did, GPS altitude is accurate to 10 to 25 metres.  Worse in built up areas.

Well, considering that everyone is saying that you can only get altitude readings with Satellites, I suppose that I would have to conclude that I have a satellite phone. 

Nooooo, its the only way a GPS system can show Altitude.. thats the only point we are making.

You're phone can get that info from a database, from an internal barometer, or it can simply guess it to make itself look important.  I't can't get that information by triangulation from transmitters based on the ground.

Google maps provide that information..