Over the past few months I have noted the VPS system on my Phantom 4 erroneously reporting that I am 5-12 feet above ground when I am flying at much higher elevations (150-400 feet). I do NOT have a gimbal guard (or any other third-party hardware) installed underneath my P4 aircraft. I HAVE calibrated both the bottom facing VPS sensors and the forward facing obstacle avoidance sensors using DJI Assistant 2 software and my computer monitor screen. I am on the latest public release P4 firmware: v1.1.411
Yesterday, I researched this issue more fully and was able to identify and repeatably demonstrate the following circumstances under which this intemittent false reporting of 5-12 feet heights by VPS sensors occurs:
1) P4 aircraft in either P-mode or S-mode.
2) P4 flying forward at full throttle at actual altitude of 100-400 feet.
3) False VPS readings occur more frequently when P4 is flying forward into a headwind, less frequently when flying forward when there is no headwind.
4) During yesterday's testing, I saw false VPS readings EVERY time I flew forward into 12-15 mph headwind, and I NEVER saw false VPS readings when flying backwards (into or with the wind).
Symptoms:
- False VPS readings of 5-12 feet height occur every few seconds, and sometimes continuously, the entire time the P4 is in full throttle (or close to full throttle) forward flight at altitudes of 100-400 feet.
- False VPS readings stop occurring as soon as throttle is reduced and NEVER occur when the P4 is just hovering (even when facing into wind).
Hypotheses:
- I believe the VPS sensors are intermittently detecting the P4 camera when the aircraft is near maximum forward tilt during full-throttle forward flight.
- The reported erroneous VPS height is typically 5-12 feet (instead of < 1 foot) because I think the CPU is averaging the very close camera detection readings (< 1 foot) with the maximum VPS system readings of 30+ feet.
Supporting evidence:
- False VPS readings of 5-12 feet only occur when P4 is in near full throttle forward flight.
- False VPS readings do NOT occur when throttle is reduced, or P4 is hovering or flying backwards.
I invite others to test this and report their experience in this thread.
I have this same occurrence when flying as noted in the OP. Not a big deal as it goes away after a second or two when flying forward max throttle not sure if this is something that can be fixed via firmware because it is a real occurrence of the VPS hitting the drone itself.
I find when flying towards the sun the vps says I'm 4 feet away from it n stops me from moving foward... pretty sure thats not accurate, I dont think the P4 could take that kind of heat, lol
What's more, if it is convenient, you can sync your flight record via DJI Go app and leave your DJI account (the email address) here.We'll look into it by checking the corresponding records so it is necessary to light up the stars of these records before syncing.
How do I "star" or "un-star" an individual flight record? I can sort flight records based on whether they are starred or not (one old record is currently starred), but I can't figure out how to star or un-star a flight record. Also, my flight records are already synced; can I still star several records and then re-sync?
I starred the pertinent flight record and sync'd my flight records to my DJI cloud account. If you post your work email address, I'll send you my account email address. I don't want to post it in a public forum.
I starred the pertinent flight record and sync'd my flight records to my DJI cloud ...
Sorry for the delay. I've discussed your issue with our developers and the DAT flies of these flights which could be downloaded via DJI Assistant 2 are also necessary (Both FC file and vision file). Posting a dropbox link of these data files are appreciated. I can understand your concern so when I get your DJI account, I'll delete your post of your account asap. Thank you for your understanding.
I transferred all the .DAT files from my P4 to my computer. But when I went to check the directory where I told DJI Assistant 2 to put all the flight and vision data files, I just found a single 3 GB file with yesterday's date. It apparently combined ALL the files from over 10 flights into a single .DAT file. How handy. And I can't access this file with DJI Assistant 2 unless I reattach the P4. How handy.
My 03 JUL 2016 flight with my Phantom 4 where I experienced numerous VPS indications of 5-15 feet VPS height while flying full throttle forward in P-mode and S-mode at an actual altitude of 98 to 226 feet has been starred in my flight records and my flight records have been sync'd to my DJI Account. As noted in my original post, previous to this flight I had calibrated the ground-facing Vision sensors and the forward-facing obstacle avoidance sensors using the DJI Assistant program on my PC. I did not have any gimbal guards or any other 3rd-party devices attached to my P4 aircraft during this flight. I believe the Vision sensors might be detecting the P4 camera when the P4 is tilted forward during full-throttle flight.
Please have your service and firmware teams examine the .DAT files and see if they can determine the cause of the false VPS readings during full-throttle forward flight at high elevations. I have seen these same false readings on numerous other flights, but on this flight I was intentionally trying to determine under what circumstances it occurred and was able to duplicate the false VPS readings multiple times.
My 03 JUL 2016 flight with my Phantom 4 where I experienced numerous VPS indications ...
Thanks for your feedback and I've deleted your DJI account in #12. I‘ll pass this case to our data analysis team. I'll post something when I get any update. Thank you for your patience and understanding.
My 03 JUL 2016 flight with my Phantom 4 where I experienced numerous VPS indications ...
Hello David. The data is under analyzing but we still need more information. Do you keep a screenshot of this? It would be better to post it here with pointing out the wrong place. Thank you.
No - I did not take any screenshots during my July 3rd flight. I am traveling on business this week, but could take some additional flights with my P4 next weekend. I can either take screen shots or might try to use the 3rd-party SHOU screen recorder app, which I haven't tried to use in many months, to record the DJI app screen in real time.
What I saw on the DJI app camera screen during forward level flight at actual altitudes of 98-226 feet while flying in P-mode or S-mode at or near full throttle was the following: at the bottom left side of the screen where the distance from home point is displayed, the display would alternate every few seconds between a) the distance in feet from home point, and b) a VPS height reading of 5-15 feet, while the barometric height displayed remained constant.
Edit：When the drone flies in strong wind and reaches large attitude, the ultrasonic may probably detect the wave reflected from the gear, which leads to the familiar issue like yours. But you don't need to worry about that since your drone works noramlly in most of the situation and the data analysis result shows the drone behaves normaly . We will keep optimizing our product to ensure the user experience. Thanks for your support again.
Thanks for your response indicating that getting false VPS readings is not unusual when flying P4 forward at max. throttle position.
I did some more extensive testing of firmware version 1.2.503 and DJI GO app version 2.8.4 this past weekend after calibrating IMU, gimbal and compass (at location). Overall, I was very pleased with the flight performance and stability of the new firmware and DJI GO app. A few areas for improvement would include: eliminating intermittent false VPS readings during full throttle forward flight in P-mode and S-mode; eliminating gimbal tilt during high-speed sideways and reverse flying; and increasing gimbal stability during high speed sideways flying into wind as noted below.
I posted the following 11-minute video on YouTube of highlights of this flight, which can be accessed using the following link:
In general, these were my findings:
1) ALTITUDE HOLD PERFORMANCE
Actual altitude hold as indicated by barometric height indicator on DJI GO app camera screen is very good under all max. throttle fights forward, backward and sideways in both P-mode and S-mode, even when stopping flight by releasing right stick, which causes the P4 to break hard. At 100 feet elevation, P4 typically stayed between 95 and 105 feet elevation. EXCELLENT!
2) LEVEL HORIZON HOLD AND STABLE GIMBAL PERFORMANCE DURING MAXIMUM THROTTLE FORWARD FLIGHT
Horizon in live camera view (and on recorded video) was very level on takeoff and throughout max. throttle FORWARD flights and during stationary turns at completion of flight segments in both P-mode and S-mode including when flying directly into wind or in same direction as wind. EXCELLENT!
3) TILTED HORIZON AND GIMBAL GLITCHES WHEN FLYING LEFT and RIGHT AT FULL THROTTLE; HORIZON TILT DURING FULL THROTTLE REVERSE FLIGHT
Horizon was noticably tilted during full throttle flights to LEFT or RIGHT, and, when flying sideways into wind in S-mode at max. throttle, the GIMBAL would twitch badly. I believe this is due to both the gimbal not being able to accommodate level flight given the extreme sideways tilt of the P4 and the force of wind on the gimbal at max velocities. Horizon would also tilt when flying full throttle in reverse. When capturing quality video one would not want to fly at maximum throttle sideways, so GIMBAL twitching during such moves is not generally an issue. However, the horizon tilt during sideways and reverse flight segments was disappointing.
4) FALSE VPS READINGS DURING FULL-THROTTLE FORWARD FLIGHT IN P-MODE AND S-MODE
At actual P4 altitude of approx. 100 feet above level ground, during full throttle flights forward in S-mode and P-mode, intermittent FALSE VPS readings of 7-15 feet would appear on the bottom of the DJI GO app camera screen and alternate with correct readings of the P4 aircraft's distance from Home Point. As we have discussed, and you confirmed with your engineers, this is most likely a result of the VPS sonar sensors detecting the gimbal when the P4 is tilted forward at about a 45-degree angle. This occurred during full throttle forward flight in S-mode (Speed mode) regardless of whether I was flying into wind or in the same direction of the wind. In P-mode, false VPS readings occurred, but at lesser % of time, and ONLY during full throttle flight INTO head wind. No false VPS readings were observed during full throttle sideways flying or during Reverse flight in either S-mode or P-mode.
Conclusion: As long as the intermittent false VPS readings do not cause any problems to flight stability or safety features (and none were observed), then I think P4 pilots can live with false VPS readings during full throttle forward flight. Perhaps engineers can tweak VPS sonar sensor programming in a future firmware update to eliminate or greatly reduce the occurrence of FALSE VPS readings during full throttle forward flight.
6) FLIGHT DATA REVIEW
If your firmware engineers are interested in reviewing data from this test flight, I have posted the following files in DropBox:
Thanks for your effort and support.I'll try to pass your test result to our developers for reference.Happy flying and when you want to record videos and take photos, please operate the drone smoothly.
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