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I have a good understanding A-GPS functionality. I understand that assisted GPS is used to improve TTFF, works better indoors but costs more as you are using the mobile networks to determine the position.

Let's say you have a simple PCB with a GSM module and a GPS module. Both modules use an antenna.

Is it possible to fully do without the GPS module and the antenna and purely rely on the GSM module to determine the position using assisted GPS? By any chance is this what smartphones do? I understand that GSM antennas come in many different shapes and sizes, but are less affected by physical mass between the antenna and the mast. However, the GPS antenna needs a clear view of the sky in order to determine the position.

If my device is going to be used indoors mostly, would I not be better off completely scrapping GPS and just using the assisted GPS functionality of the GSM module?

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  • \$\begingroup\$ How exact do you need your position? GPS has several orders of magnitude better precisition. \$\endgroup\$ – Turbo J May 4 '16 at 11:23
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    \$\begingroup\$ Have you read the wikipedia article on A-GPS: en.wikipedia.org/wiki/Assisted_GPS ? A-GPS is a way to provide an estimate of the location so that the GPS has a better starting point. Without the GPS part you will only get a "rough estimate" of your location. \$\endgroup\$ – Bimpelrekkie May 4 '16 at 11:28
  • \$\begingroup\$ A sensitive GPS receiver can get a fix indoors, but the signals have normally been reflected so much about the best position you'll get is within a few meters of the house, GSM is much worse (as per the answer) so neither will work well unless you just want to work out what house a person or object is probably in. \$\endgroup\$ – PeterJ May 4 '16 at 11:37
  • \$\begingroup\$ Thanks all. I think the combination of A-GPS and a high sensitivity GPS should do the job! \$\endgroup\$ – jskidd3 May 4 '16 at 11:52
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    \$\begingroup\$ A-GPS provides data to better/faster interpret GPS satellite data for a position fix. It does not itself provide any positional information. \$\endgroup\$ – JimmyB May 4 '16 at 13:45
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It is possible to get a location fix without a valid GPS signal. Cell phones often call this "network location". I wouldn't call it A-GPS, but sources are conflicted here.

This fix is not very accurate, depending on the size of your current cell between several 100m and several kilometers. Not suitable for indoor navigation.

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  • \$\begingroup\$ This is definitely NOT A-GPS \$\endgroup\$ – Daniel May 4 '16 at 11:32
  • \$\begingroup\$ de.wikipedia.org/wiki/… lists network location as a variant for A-GPS, the english version does not \$\endgroup\$ – Christian May 4 '16 at 11:34
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    \$\begingroup\$ As far as A-GPS stands for "assisted GPS", and GPS being the American global positioning system (not a generic location-determining system) anything that doesn't actually use GPS seems pretty badly misapplied. \$\endgroup\$ – Daniel May 4 '16 at 11:35
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Location can absolutely be achieved without a GPS antenna. However, the accuracy of GPS is approximately 3 meters, while GSM is as high as 50 meters. If you are intent on positioning using cell-towers (network positioning) then check out opencellid

On the other hand, you might look into "wifi positioning". This relies on RSSI signal strengths of nearby wifi networks. Public wifi hotspots are becoming common enough that this technology is improving rapidly.

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