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Installed - Ublox M8N Glonass GPS / Compass

Discussion in 'Phantom 1 Discussion' started by JKDSensei, Dec 9, 2015.

  1. JKDSensei

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    Finally installed my Ublox GPS.

    Install was easy and djisquare helped a bit. I'm getting upwards of 16 sats now. (better than my P3)
    Lock on time is no better tho. Sill about 60 seconds.

    A few installation notes from my install.....

    1). Be SURE to reinstall the OEM shielding that covered the OEM compass even though you will probably install the Ublox ontop of the P1. Without it, the GPS will get too much interference from the Naza.

    2). After installation, it can take up to 20 minutes for first lock on. This is due to the nature of GPS devices that have never been initiated in a particular region or have been dormant for a long time. Lock on times will drop dramatically the more you use it in your home area.

    3). You can completely remove the original Compass. The Ublox M8N has built in compass.

    4). I installed the device on top of my P1 using two way tape and made a small precise pass through hole using a dremel tool.

    According to some GPS related sites, after your receiver finds a new signal, it needs to listen for 30 seconds to receive current ephemeris data (which describes exactly where the satellite is located) for EACH NEW SATELLITE. If the signal is lost during this time, the process for that particular satellite needs to start again. But some GPS receivers have technology that caches satellite data which can considerably shorten sat lock times. 3.5 minutes for 7 satellites w/o expediting routines.

    So I feel much better now knowing I have a much more advanced GPS / Compass (critical to every Phantom mission)

    It was about $30
    Installation time about 30 minutes
    Remove upper shell
    Remove (and save) gray electrical noise shield
    Remove OEM GPS
    Replace gray electrical noise shield
    Make provision to run Ublox Cable through shell (Ublox GPS mounts on top of P1)
    Mount Ublox GPS (I mounted mine on top of the P1 with 2 way tape
    Connect Cable to existing GPS connector
    Remove OEM Compass from Leg (Ublox GPS has built in compass)
    Replace upper shell
     
    #1 JKDSensei, Dec 9, 2015
    Last edited: Feb 7, 2016
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  2. Pilot_FML

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    Informative post... thanks for sharing.

    Refresh my memory.... why did you R&R the original GPS unit?

    60 seconds to acquire enough GPS satellites doesn't seem excessive to me....

    P.S. Surprised to hear that your new GPS unit took so long to acquire satellites on the initial lock on attempt. I've never heard of that before. Maybe it was just the time of day and where satellites were in your particular location.
     
  3. JKDSensei

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    Thanks Pilot,
    I did this because I felt the Ublox was far superior to the old OEM GPS / Compass.
    The GPS and compass I removed were both excellent. I often locked 10 -11 sats with original GPS.
    And so far, the OEM locked considerably faster than the Ublox and I was expecting sat lock times in the 15 - 20 second range but that didn't work out.

    Another reason I changed it is because according to my Flytrex data, the sat count with the ORIGINAL GPS would sometimes drop as low as 9 sats in clear weather while IN FLIGHT. To me that was too close to the borderline.

    Another member with the same mod is telling me he gets sat lock (green only blinking light) in 20 seconds. I'd love that.

    I plan to try powering up the P1 in another area and see if the sats lock faster. Could be interference like you said.
     
    #3 JKDSensei, Dec 10, 2015
    Last edited: Dec 11, 2015
  4. JKDSensei

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    Update....

    Last night I took the P1 out to an open area (the previous site was far less than ideal) and tested sat lock times again. Mostly clear skies.
    On this test FIRST sat lock (steady green blinking GPS light) occurred in 51 seconds (THAT'S more like it)

    On the next flight, (15 minutes later) full sat lock occurred at only 33 seconds (now we're talkin)

    In addition, in flight performance was also much better. Maximum in flight sat count (on my P1) in all flights stabilized at 16 satellites. YES!
    My P1 is locking 16 sats consistently....heehee.
    That's a little better than the 14-15 my P3A usually gets in flight under those (or better) conditions.
    I would say the Ublox is a good upgrade across the board no matter what Drone you fly. (provided I don't have a fly away or navigation related crash now).
    I would think that would be less likely since the Ublox is a considerable upgrade and has a 32 bit processor vs the original GPS's 8 bit processor.

    Time will tell.
     
  5. Pilot_FML

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    Glad that you like your new new GPS/Compass setup...

    A lot of factors go into getting good GPS locks, so you definitely will see it change from minute to minute and from place to place.

    I'm not sure why the old setup acquiring 10-11 satellite locks wasn't sufficient though. Even, if the worst happened and your satellite lock-ons dropped to 9, that would 3 more than necessary for 100% accurate GPS positioning. Anything more than 6 is really overkill...
     
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  6. discv

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    JKD, have you got the link for the device you used?
     
  7. JKDSensei

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  8. JKDSensei

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    Flyaway prevention? Also, I like upgrading my P1.
    I had no "real" reason to upgrade.....I just like doing things like that.

    It does seem to lock on faster (that's a plus) and it locks onto far more satellites (navigation redundancy in flight is a good thing). First flight lock on is about 50 seconds and subsequent flight lock on times are around 30 seconds. 16 satellites seems to be consistent. The additional sats does give you better position accuracy btw.

    For $40.00 I felt it was a good investment in my beloved and trusty P1.
     
    #8 JKDSensei, Dec 11, 2015
    Last edited: Dec 11, 2015
  9. Pilot_FML

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  10. Pilot_FML

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    No explanation necessary about why you tinker with your P1.... I feel the same way.

    Just a little feedback on your comment..... "The additional sats does give you better position accuracy btw."?

    I tried to dig up the source where it was explained to me that only 6 satellites are necessary for exact position accuracy but I couldn't find it. I'm pretty sure it was from one of the three DJI guru's on the original P1 rcgroups thread that taught all of us much about the P1.

    The only explanation I could now find was in the following link:
    Accuracy of GPS data - OpenStreetMap Wiki

    Granted Wiki sources aren't always true but if you follow the narrative it makes sense. Only 4 (not 6) satellites are all that appear to be needed for complete position accuracy.

    BTW, I still think of both of my P1's as trusted workhorses that never let me down. Flying them 3 years ago was and still is something that brings a smile to my face......
     
  11. JKDSensei

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    Here's the technical discussion I read and why more is better....(at last according to this Guru) :)
    How many GPS channels make sense?

    But to quote the site in summary....
    • Speeds up satellite acquisition
    • Reduces power consumption
    • Reduces likelihood of losing a 3D fix even in urban canyons
    • Provide better sensitivity, allowing fixes in dense forests, and even in some tunnels
    • Provides better positioning accuracy


    I find the P1 to be MUCH more relaxing to fly and the fact that I've customized it to my liking is a plus.
    I take the P1 on missions very often. Still my No1 goto UAV.
     
    #11 JKDSensei, Dec 11, 2015
    Last edited: Dec 11, 2015
  12. discv

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    Thanks JKD for the link. Done the same job using the DJI gps module- but I want to put that back on my 550.
    Not flown it yet- but I think the CoG will need tweaking

    . hybrid.jpg
     
  13. Pilot_FML

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    Well I guess your guru trumps my guru....;)

    Thanks for taking the time to find this link. I learned where I was wrong in my thinking....:eek:

    I think I'm going to actually find out how many GPS satellites I'm continuous locked onto by looking at a Flytrex add-on.
     
  14. JKDSensei

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    Well not so fast.... :)
    That's just one source. But I do believe I read the same from other sources.

    I have Flytrex Core 2 and I'm glad I installed it. Until I decide to install an iosd (I already have FPV), it's the next best thing.

    As far as the P1....
    My thinking is that you're better off with the Ublox.
    Supposedly better GPS AND Compass than the originals. I've done about 5 flights so far and all is good.
    My gut feeling is some of reported flyaways could have been due to failure of one of those
    (although it could have just been that terrible insecure connector vibrating loose)
     
  15. Pilot_FML

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    I think what the link discusses makes it pretty reliable because its careful to note that its a simplified explanation and that it isn't 100% technically accurate.

    At this point I'm really curious how many GPS locks I get with my P1.1.1's over the course of a normal flight. I can see why having a lot channels available improves the odds of always having the minimum of sats available to get at least 4 sat locks.

    What I'd really like to find out is how many GPS channels the stock P1 Naza M-V2 makes available. Any idea??

    I'm going to see if I can find out but in the interim I'm also going to look into the Flytrex Core 2.... Christmas is coming :)
     
  16. JKDSensei

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    I have FlyTrex Core 2 and I'm glad I bought it. Lot's of good info. Easier to install than the GPS imo.

    With the OEM standard GPS that comes with the P1.1.1 I routinely locked between 9 to 11 satellites.
    Some flights less of course. Depending on what's in the sky (as far as SATS available) and weather conditions etc.
    Some flights I later found (looking at Flytrex data) that I had as few as 8 sats That concerned me as I don't like to be 300ft up and 1500ft away with very low sat lock count.

    Now, with the Ublox, I'm routinely locking 16 sat. MUCH better!
    But not only that....it seems to stabilize on that count better. With the standard GPS the sat count would fluctuate more.
    Now it seems to get and hold 16 sats for the entire flight once airborne.


    HAL 9000....
    "My mind is going......I can feel it....."
     
    #16 JKDSensei, Dec 13, 2015
    Last edited: Feb 7, 2016
  17. Pilot_FML

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    I guess I'm lucky where I fly because I get the >6 locks (no red flashes) very quickly after I insert the flight battery.

    The reading I've just begun doing about the FlyTrex Core 2 has convinced me that its an easy mod and one that adds all kinds of possibilities. Add to that the bells and whistles that Dashware software provides, and that pretty much sews up what I'll be learning about in the next few "non-flying" months. ;)

    After I install the FlyTrex module (and play with Dashware software), I'll have a little better feeling of whether or not I get dangerously near a low number of satellite locks during one of my typical flying days. It will be an interesting experiment ....
     
  18. JKDSensei

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    I don't think you'll find anything alarming. I expect you'll find what I did. Especially since you haven't had any issues while flying.
    I've practiced manual flight enough to not worry about loss of GPS and I always remain LOS. Regardless of orientation. That really makes a difference. :)

    It really pays to get a $40 - $50 UAV such as a Syma X5C and learn to fly it manually. That experience can save your butt if the Phantom loses GPS for any reason.

    You may have already done this and can fly circles around me....just suggesting it to others who may not that read this whenever.
     
  19. Pilot_FML

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    Since I get sufficient GPS locks quickly and almost every time (and wherever) I fly you're probably right. I'm just very curious about what happens as I put some distance between the quad and myself.

    I fly only LOS ... can't get comfortable just looking at an FPV screen.

    I fly in ATTI mode at least half the time I'm in the air. It's the only way to be ready in case something goes amok with the GPS and it also renders better AV.

    The Syma X5C is something I've considered but I'd need a bigger living room to really enjoy it and not worry about my wife catching me flying inside...:oops:

    For the moment, the small Proto-X and RealFlight simulator I have will have to do..:):)
     
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