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Thread: Adding GPS to my RPi2

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    Passenger skyspotter's Avatar
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    Adding GPS to my RPi2

    Got a small USB with cable GPS receiver (Earthmate LT-20) and thinking if it could be integrated to my FR24 feeder ADSB receiver. I was able to run it using other Linux distros and hoping it will work on RPi2. I want it to run together with FR24 feeder. If this question already exist please point me to the link. Thanks

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    What do you hope to achieve with adding one.

    The FR24 supplied boxes use GPS for time and location accuracy.

    With USB TV sticks and the software we install your location is specified at the time of setup and time is sycnronised with NTP via the software calling it like others around you with the same devices. A GPS will likely only add time adjustments that NTP will then fight.
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    Passenger skyspotter's Avatar
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    I see thanks for the input. I was thinking it could help the feeder to be more accurate aside from what i provIded during the setup. Anyway, i wont bother to add it on my box. I will maybe do other expirement with it. I appreciate your answer.

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    Team FR24 Mike's Avatar
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    The only GPS units that FR24 is using is the one connected to the FR24 box. Using a USB port to connect a GPS destroys most timing, because of USB latency.

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    Passenger skyspotter's Avatar
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    Got it Mike. Thanks for the helpful info.

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    Mike,
    Would a GPS receiver that uses the GPIO on the RPi work any better than a USB GPS device?
    Thanks

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    Quote Originally Posted by StupidDoes View Post
    Mike,
    Would a GPS receiver that uses the GPIO on the RPi work any better than a USB GPS device?
    Thanks
    Yes, there is a pulse per second feature built in the ntp, driver 22. If you use this with a GPS derived PPS signal, connected to one GPIO of the Raspberry, its system clock will sync much more precisely than with clicks from other NTP servers around. NTP will manage this well without letting the PPS signal fight against the other time sources. Accuracy will become as good as some few microseconds rather than a couple of milliseconds without PPS.
    To make things better: using a serial GPS receiver, you might provide position and time with much less jitter than via USB. The PPS thing is not dependant on any GPS position feed though. PPS is NTP-related.
    Do not expect the setup as a plug and play one. There are bad GPS receivers out there. You have to tweak things.
    By the way: As far as I know, the flightradar application does not improve with precision of the system clock. Even the MLAT thing cannot participate from a better system time (yet?).

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    Do not expect the setup as a plug and play one. There are bad GPS receivers out there. You have to tweak things.
    So what GPS module would you recommend?? I was looking at one of the microstack ones off ebay?

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    Sorry, newbies on this forum are not allowed to post links.

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    The simple point is, Investing in a GPS unit won't help anyone currently and will be a waste.

    The software is hardcoded to probe NTP periodically and sync before sending data as part of its processing. Adding a device won't change that.

    (unless of course you have it for other reasons outside the FR24feed process)
    Last edited by Oblivian; 2016-01-05 at 22:17.
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