Welcome to PhantomPilots.com

Sign up for a weekly email of the latest drone news & information

GPS Indoors-how does it work?

Discussion in 'General Discussion' started by npalen, Apr 2, 2014.

  1. npalen

    Joined:
    Mar 12, 2014
    Messages:
    532
    Likes Received:
    8
    Location:
    Kansas
    I'm amazed that the FC40 can pick up a sufficient number of satellites in my one story home. How does this work since GPS is a line-of-sight system?
     
  2. Ksc

    Ksc

    Joined:
    Jul 6, 2013
    Messages:
    973
    Likes Received:
    4
    Location:
    Naples, FL
    its not line of sight. it works the same way your gps in the car works if you go through a tunnel or the way it works on a submarine.
     
  3. Cr8tive_leo

    Joined:
    Feb 6, 2014
    Messages:
    255
    Likes Received:
    1
    Location:
    Ontario, Canada


    ... really ... :shock:

    It is line of sight, windows don't obstruct the signal like concrete and gerters. Submarines use sonar and precise mapping under water (and other tech), m-band gps is military grade and submarines can only use it when surfaced or at perscope depth, gps does not penetrate water, totally different than our civilian gps.

    When you go through a tunnel agps usually kicks in, assisted gps... blah... blah blah... :cool: :mrgreen:
     
  4. ZonComGMZ

    Joined:
    Dec 8, 2013
    Messages:
    189
    Likes Received:
    1
    I sure hope the U.S. naval fleet isn't using Garmin or TomTom units to find their way around the oceans :)
     
  5. ianwood

    ianwood Taco Wrangler
    Staff Member

    Joined:
    Jan 7, 2014
    Messages:
    4,910
    Likes Received:
    1,789
    Location:
    Lost Angeles
    GPS is LOS. Almost all satellite services are. It generally doesn't work indoors though many receivers can pick up a couple SVs through windows or even the roof depending on construction. At 1.2 and 1.5GHz, there is some room to penetrate thinner porous materials but it is not designed for indoor use.

    The navigation system in your car uses an IMU and magnetometer to figure out your heading and rate of motion when it loses GPS signal such as when you drive into a tunnel. And as far as I know, submarines have to surface to get a GPS fix and use IMU based navigation and dead reckoning when submerged.

    A-GPS is really only used to facilitate a faster time to first fix and not filling in GPS gaps. Cellular triangulation and WiFi location are also often baked into non-GPS location services.
     
  6. Ksc

    Ksc

    Joined:
    Jul 6, 2013
    Messages:
    973
    Likes Received:
    4
    Location:
    Naples, FL
    Well then I'm wrong. Although it doesn't explain how I get perfect GPS lock in the local high schools gym. Thing has no windows and it's a concrete bunker. Literally a bunker. It's a hurricane shelter as well.
     
  7. ianwood

    ianwood Taco Wrangler
    Staff Member

    Joined:
    Jan 7, 2014
    Messages:
    4,910
    Likes Received:
    1,789
    Location:
    Lost Angeles
    Concrete is porous. I get 7 or 8 satellites in my workshop which has a concrete ceiling.
     
  8. Cr8tive_leo

    Joined:
    Feb 6, 2014
    Messages:
    255
    Likes Received:
    1
    Location:
    Ontario, Canada
    ... Hmmm ... I'd look it up to be sure there. Just saying. AGPS is called Assisted Gps for a reason. :cool:


    '...Cellular triangulation and WiFi location are also often baked into non-GPS location services....' That's AGPS right there, when gpS signal is bad, or having problems. Has nothing to do with faster first fix.

    I've been decoding nmea output for what seems like eons. Don't argue, listen to the master... LOL... :ugeek:
     
  9. sar104

    Joined:
    Mar 22, 2014
    Messages:
    1,265
    Likes Received:
    245
    Location:
    Los Alamos, NM.
    There's definitely no substitute for being confident and assertive - especially when you are completely wrong. A-GPS has everything to do with faster initial fix - that is what it is for. If you had looked it up you would have discovered that for yourself.
     
  10. npalen

    Joined:
    Mar 12, 2014
    Messages:
    532
    Likes Received:
    8
    Location:
    Kansas
    So I guess that penetration of my wood frame construction is a piece of cake compared to concrete.
    Interesting stuff, guys! Thanks for the input.
     
  11. sar104

    Joined:
    Mar 22, 2014
    Messages:
    1,265
    Likes Received:
    245
    Location:
    Los Alamos, NM.
    The modern chips are are very sensitive and low-noise devices, able to pick up the weak signals that penetrate or leak into structures remarkably well.
     
  12. Cr8tive_leo

    Joined:
    Feb 6, 2014
    Messages:
    255
    Likes Received:
    1
    Location:
    Ontario, Canada

    LOL... here's a hero cookie. Agps is useless when there is no wifi or cell reception.
     
  13. sar104

    Joined:
    Mar 22, 2014
    Messages:
    1,265
    Likes Received:
    245
    Location:
    Los Alamos, NM.
    A-GPS simply speeds up acquisition of the almanac and ephemeris data via cell and/or wifi. Lack of those doesn't prevent GPS signal lock though, and the presence of them is not a substitute for GPS, since they do not actually provide location data.
     
  14. Cr8tive_leo

    Joined:
    Feb 6, 2014
    Messages:
    255
    Likes Received:
    1
    Location:
    Ontario, Canada

    Exactly, that's why it's called Agps. :cool:
     
  15. sar104

    Joined:
    Mar 22, 2014
    Messages:
    1,265
    Likes Received:
    245
    Location:
    Los Alamos, NM.
    OK - so if you understand that A-GPS is just a mechanism to speed up GPS signal lock, and not an alternative location service, then what was the point of your first post in which you argued the exact opposite?