GPS signal on devices

Guest2 · 4 Feb 2015 at 20:00

I'm not sure if this is sport / mobile / IT equipment or what so have left it in here.

How come devices specifically built with GPS in mind cannot pick up GPS signal in doors? However mobile phones have no problem picking up GPS when inside

[TW]Fox · 4 Feb 2015 at 20:03

Because the mobile phone isn't using just GPS for position, it's also using wifi etc as well.

GPS requires line of sight to a satellite.

Salsa · 4 Feb 2015 at 20:03

Don't phones use a combination of a number of signals (GPS, Network, WiFi) to give you a location whereas a GPS watch for example has to have a clear line of sight to the satellites?

/Salsa

Edit: Fox is reading my mind... time to put on the tinfoil hat.

Werewolf · 4 Feb 2015 at 20:06

Fox got it dead on

GPS tends to require LOS to a satellite, most phones that use GPS supplement that with things like known wifi locations to give "assisted GPS".

DJMK4 · 4 Feb 2015 at 20:06

Put it near a window it "may work" but as said, line of sight

Guest2 · 4 Feb 2015 at 20:22

In that case wouldn't it be better to integrate some sort of network service like 3G into GPS specific devices?

Ski tracks on my mobile works perfect in the mountains - no line of sight as its in my pocket

robj20 · 4 Feb 2015 at 20:28

The radio signal can pass through things like glass, plastic and clothes.

Werewolf · 4 Feb 2015 at 20:37

Guest2 said:
In that case wouldn't it be better to integrate some sort of network service like 3G into GPS specific devices?

Ski tracks on my mobile works perfect in the mountains - no line of sight as its in my pocket

3G isn't very useful on it's own for location though*, and requires both a lot more processing power and a working sim to do it.
GPS can and does work on it's own with no requirement to communicate back.

*It can tell your rough area based on the mobile phone cells you're in, but to get a reasonably accurate fix tends to require the mobile phone masts to communicate back to your device based on it's signal (your phone won't know where the mobile phone masts are and IIRC actually requires the signal from the phone to be worked out on two or three+ masts).

DJMK4 · 4 Feb 2015 at 20:37

Also,why would you want to use GPS indoors

Caged · 4 Feb 2015 at 20:44

For indoor mapping there's BLE beacons.

GeX · 4 Feb 2015 at 21:16

[TW]Fox;27584667 said:
Because the mobile phone isn't using just GPS for position, it's also using wifi etc as well.

GPS requires line of sight to a satellite.

They won't always require LoS. I have two phones, one can lock onto ~7 satellites when indoors and the other cannot lock onto any.

This is checking using GPS Status, not just looking on Google Maps for a location.

Colbaker · 4 Feb 2015 at 22:14

Guest2 said:
In that case wouldn't it be better to integrate some sort of network service like 3G into GPS specific devices?

Ski tracks on my mobile works perfect in the mountains - no line of sight as its in my pocket

Do you get a phone signal in the mountains? If not then using A mobile network would be pointless, does the GPS have to have at least 3 satelliteso to "triangulate" your position?

DIABLO · 4 Feb 2015 at 22:36

My Garmin GPS bike computer seems to able to get a sat lock in a brick and mortar building.

Guest2 · 4 Feb 2015 at 22:37

Colbaker said:
Do you get a phone signal in the mountains? If not then using A mobile network would be pointless, does the GPS have to have at least 3 satelliteso to "triangulate" your position?

Yes. I always had 3G and good cell signal (Tignes / Val d'isere)

I'm not sure on the triangulation question

DJMK4 · 4 Feb 2015 at 22:38

DIABLO said:
My Garmin GPS bike computer seems to able to get a sat lock in a brick and mortar building.

Depends on the GPS chip and power of the device, quality of the chip

Is SIRF star III still the best one?

Edit: seems so, remember having an extranal gps card for my dell PDA where I using tomtom locked on to sats in no time

SiRFstarIII

SiRFstarIII architecture is designed to be useful in wireless and handheld location-based services (LBS) applications, for 2G, 2.5G, 3G asynchronous networks. The SiRFstarIII family comprises the GRF3w RF IC, the GSP3f digital section, and the GSW3 software that is API compatible with GSW2 and SiRFLoc. The chips have been adopted by major GPS manufacturers, including Sony, Micro Technologies, Garmin, TomTom and Magellan

http://en.m.wikipedia.org/wiki/SiRF#SiRFstarIII

Guest2 · 4 Feb 2015 at 22:59

SiRF star III appeared in 2006. Its now up to SiRF star V I believe.

My Garmin 910XT uses SiRF star IV and cannot detect satellites indoors

DJMK4 · 4 Feb 2015 at 23:04

External GPS antenna or find a unit which has reports from people working indoors