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Weak GPS?

Discussion in 'Phantom 2 Vision + Discussion' started by MikeySoft, May 14, 2014.

  1. MikeySoft

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    The other day (May 12) my p2v+ had problems maintaining 6 GPS SATs. I waited longer then the usual time before takeoff. It would have between 6 and 5 sat once in the air, and as expected, go in and out of GPS mode. I took it up little higher above the house and trees in the hope it would get more GPS SATs. It acted the same.

    The next day it had no problems getting up to 10 GPS SATs.

    Has anyone else experience this? I wonder why this happened?
     
  2. Geoelectro

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    GPS signals can vary from day to day sue to several factors. Cloud coverage, sun activity etc. (moonspots?)

    Geo
     
  3. MikeySoft

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    It was a sunny day.

    It was also the first time I flew in not GPS mode, an interesting experience.
     
  4. MikesTooLz

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    GPS satellites are floating in space circling the earth constantly moving.

    You will never have the same satellites above you at the same location, whatever ones are above you and within range are all you will get. If for any chance the ones you can see at that time are not positioned in such a way to be around you or having a good amount of distance between them you will not get a good triangulation.


    For this reason your GPS accuracy can not only vary by the day, but it can actually vary by the minute as the satellites above move across the sky.

    if you have an iphone there is a free app called P-Tracker Satellite Viewer. This will show what GPS satellites are currently above you, where they are located and where they are moving.
     
  5. cougar

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    Where did you get that information from?
    GPS satellites are stationary in relation to earth in orbiting us. How else could position be calculated?
    "The Global Positioning System (GPS) is a space-based satellite navigation system that provides location and time information in all weather conditions, anywhere on or near the Earth where there is an unobstructed line of sight to four or more GPS satellites.[1] The system provides critical capabilities to military, civil and commercial users around the world. It is maintained by the United States government and is freely accessible to anyone with a GPS receiver."
     
  6. FrankPA

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    Actually, Cougar, Mike is exactly correct!

    GPS satellites rely on internal atomic clocks and the fact that at a certain distance from the GPS the clock pulse will be delayed by a certain amount according to the time shift due to distance. A GPS program knows where a given satellite is at a certain time and then calculates the apparent differential in time to determine a circle on the earth along which you are the correct distance from that satellite. By triangulating the intersections of circles from several different satellites, you can plot your position on the surface of the earth.

    The satellites are not even near a geosynchronous orbit and are, in fact, traveling quite quickly over the surface of the earth.
     
  7. MikesTooLz

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    Where did I get that information? that just how they work, its a known fact... do another google search.


    GPS satellites are not in a Geosynchronous orbit.
    Satellites can triangulate their own location by receiving signals from multiple locations on earth that are broadcasting stationary location points. Once they know their own location relative to those signals from earth they can then broadcast the satellites GPS location along with atomic clock information so that any devices receiving this information can triangulate its current GPS location.
     
  8. MRSpyder2U

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    Well, butter my butt and call me a biscuit! I would have lost money on this! Mike is right. They are NOT in geosynchronous orbits.

    "The Global Positioning System (GPS) is a constellation of about 24 artificial satellites. The GPS satellites are uniformly distributed in a total of six orbits such that there are four satellites per orbit. This number of satellites and spatial distribution of orbits insures that at least eight satellites can be simultaneously seen at any time from almost anywhere on Earth. The GPS satellites circle the Earth at an altitude of about 20,000 km (13,000 miles) and complete two full orbits every day. The GPS satellites are not in a geostationary orbit, but rise and set two times per day. Each satellite broadcasts radio waves towards Earth that contain information regarding its position and time. We can receive this information by using special receivers, called GPS receivers, which can detect and decode this information. By combining signals transmitted by several satellites and received simultaneously, a GPS receiver can calculate its position on the Earth (i.e., its latitude and longitude) with an accuracy of approximately 10 m. There are more sophisticated receivers that can be used to determine position with an accuracy of a few millimeters."

    http://www.cfa.harvard.edu/space_geodesy/ATLAS/gps.html
     
  9. cougar

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    Actually, Cougar, Mike is exactly correct!

    GPS satellites rely on internal atomic clocks and the fact that at a certain distance from the GPS the clock pulse will be delayed by a certain amount according to the time shift due to distance. A GPS program knows where a given satellite is at a certain time and then calculates the apparent differential in time to determine a circle on the earth along which you are the correct distance from that satellite. By triangulating the intersections of circles from several different satellites, you can plot your position on the surface of the earth.

    The satellites are not even near a geosynchronous orbit and are, in fact, traveling quite quickly over the surface of the earth.[/quote]

    I stand corrected, thank you for the info
     
  10. Meluk

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    I too am struggling to get over 5 sats before take off. Is the Phantoms requirments of 6 minimum sats a lot higher than say satnavs?

    I know smart phones don't just rely on sats but also use wifi and cell data so we can't compare smart devices to our Phantoms.

    I'm sure I recall my old satnav showing a 7/8 sat lock on from my dining room window. Put my Phantom there and I bet it won't get over 4!


    Also, my p2v+ appears to really struggle to get sat lock compared to my P1. I hope it's not the p2v+ and instead an environmental/temporary gps issue.


    Sent from my iPhone using Tapatalk
     
  11. RedRyderMedia

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    Thanks for the info.....I downloaded the app, but need the instructions.....looking to learn, ELI5....maybe you could point me in the right direction.
     
  12. MikesTooLz

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    Mine takes about 1 minute (just a guess).

    I turn it on, wait for my phone to see the wifi and join the wifi, I fire up the vision app and have to wait maybe 30 seconds for it to go from 5 sat's to 6. Longest Ive waited was one time about 2 minutes.
    Once I'm up in the air I get around 8-11 sats.
     
  13. MikeySoft

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    I had a p2v before the plus. The p2v never had this problem. Maybe it was just back luck? I also understand a GPS system must update/download tables to know what SATs to look for. Maybe this was the problem?

    I found an android app which displays GPS SATs over head and shows how strong the signal is. I'll check it should this happen again.
     
  14. MikeySoft

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    I had my p2v+ on for a long time while this was happening. I ran it until the battery warning when I gave up hoping it would stay with 6 or more SATs.
     
  15. Mori55

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    I've had days where struggled to get 6 sats, then other days where I had sats up the kazoo! Been a lot of solar activity going on.
     
  16. gilmbento

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  17. frankycro

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    To introduce myself: Vladimir from Croatia, I fly with all possible types of multirotors, for fun and for the profession, I also assemble them.
    I recently bought the Phantom V2+ to test it, and everything is so cool except this:
    http://youtu.be/e8g9vSLINZg
    Video is from my friend who has an identical problem on his Phantom V2+.
    What do you guys think about this problem on Phantom 2 Vision plus?
     
  18. Mori55

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    Look at the post right before yours , click on the link. Should answer your question.