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Altitude again...

Discussion in 'Phantom 2 Vision + Discussion' started by rtg, Dec 20, 2014.

  1. rtg

    rtg

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    Having received my P2V+, V2 a couple of weeks ago I have been reading, watching others experiences, and recommendations. All updates have been installed and all calibrations completed. For the IMU it was the advanced calibration.

    I have read that the altitude readout on the Vision app is based on the IMU altimeter. It is not accurate. However in the link I have provided it is clear that, as a percentage of error, it is way off. Look at the distance from the Vision app station to the P2V+ when on the ground. This is a reasonable estimate. While watching the ascent the altitude is no way close when comparing to the distance measurement. I realize the distance is the hypotenuse of the triangle but should be close the altitude.

    Video here: http://youtu.be/oQ56k1gRScw

    So the question that I have not been able to find an answer is, does the Ground Station app use the GPS altitude data or IMU altimeter?

    Also I found it interesting the GPS receiver dropped several sats while at altitude.... The additional GPS EMI shielding has not been implemented.

    Thanks in advance.

    Rob
     
  2. iswimmer

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    The distance reading is the horizontal distance from the home point to the phantom rather than the straight line distance.

    The altitude reading is from the IMU. Ground Station app uses the IMU altimeter. If you start it up cold then as it warms up the altitude will be off on the high side. If you want a more accurate altitude then let it idle for a while or fly for a bit, for a whole battery if you want. Then shut down the battery. When you restart, without letting it cool, it the altimeter will set at zero and will be already warm so the altitude won't drift up so much as it flies.
     
  3. rtg

    rtg

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    Thanks for the replay. I should have pointed that this was the second flight on the same battery. The P2V+ had been outside for around 10 to 15 minutes before this flight. The temp was around 28F.

    Rob
     
  4. rtg

    rtg

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    Slight change from the altitude discussion.

    I implemented the GSP copper tape EMI reduction mod. Notice the improvement in GSP sat received as well as them being stable today. Granted the available sats do change hour by hour. However, this is another data point that indicates that this mod is a must for anyone with a version 2 of the P2V+.

    Here is a link to the video:

    http://youtu.be/A5dHdAy6s6k

    A little more snow today. Great flying weather!

    Rob
     
  5. Larry L

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    rtg, You are not joking about better GPS reception. It would of been pretty nerve wracking trying to fly & make sure you had enough satellites to fly in GPS mode before you did the mod.
     
  6. rtg

    rtg

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    Larry,

    Looking at the first video you can see I start with GPS lock but in the middle of the flight the number of sat drops, losing lock.

    Would not be good if in the middle of a Ground Station mission.

    Rob
     
  7. singapore_phantom

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    The display on my Garmin GPS unit shows not just the number of satellites, but also the degree of connection, i.e. whether it's a solid hook-up or a barely-there one. Satellites close to the horizon tend to have iffy signals. Solar issues and weather also may have an effect. IOW, the number of satellites tends to fluctuate, particularly when the receiver is moving about.

    It would be great if you guys could check http://satpredictor.navcomtech.com/ on the days of your sorties. This way, you'll be able to home in a bit more on your GPS issues.
     
  8. rtg

    rtg

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    I have been checking that website as a quick rough estimate. However, use a cell phone to get a more accurate view of how many sats are in view before flying. Now with the EMI mod the P2V+ is more inline with the phone.

    FWIW.

    Rob
     
  9. Larry L

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    Rob, That is what I was talking about. I was watching it & the second vid, you were GTG!
    Larry
     
  10. nucadude

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    There is a simple mod. that can greatly improv the sat. GPS reception. By moving the GPS cable to under the GPS shield instead of leaving on top of the shield you will immediately notice the increase in GPS Sat reception. I have even had 6-7 Sat inside my house and as many as 10-11 outside. Have not flown yet as the temperature here in Denver area of Colorado have been in the range of 9-18 F with some in the low to mid 30's F, so can only vouch for the inside GPS sat reception. will update information as soon as fly outside. The plus of this mod. is that you are not adding any material just altering location and according to the DJI locally does not invalidate the warranty.

    My question for the group is with the V2 modification and with installation of the new Phantom 2 Static Proof Compass, Part 18, what should the IMU Calibration data be, especially for the compass "Mod"?
     
  11. rotorwash

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    maybe dumb question but how do you get the video with the ground station info. I only get the raw video when I record meaning just the view from the camera.
     
  12. rtg

    rtg

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    I used an Android app called Shou screen recorder. Then I took the recorded video from the Phantom camera and placed it on top of the Shou screen recording.

    I did not have a telemetry recorder like Flytrex so this is the next best thing.

    You Android device has to be rooted for this app.

    Rob
     
  13. Dartmoor Dave

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    There is also an android app that will work on a non rooted phone and enables screen recording to be done very easily. The app is Mobizen and recording a smartphone screen is just one of the features it offers. You will need Android 4.2 or later versions in order to use it though.
     
  14. crash1sttime

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    Just downloaded Mobizen, what a great little app, now i can put my telemetry data onto the videos i do.