Hover Altitude Up and Down

r62ewa · May 20, 2016

While hovering to film myself and son at the playground my Phantom would vary in it's hover altitude up and down ~5-7 ft, go down then up again. It was hovering at ~12 ft above ground when this was happening. Will calibration possibly fix this issue, IMU?

Phantomix · May 20, 2016

I dont think an IMU calibration would fix it. the IMU is for horizontal movement, not vertical, but im not 100% sure. You may as well try though... I would suggest trying it somewhere else, and was there much wind?

r62ewa · May 20, 2016

No wind. It's the first time I've done an extended hover where I could watch the drone close up, I could hear the motors speeding up as it would regain altitude after a drop.

John Locke · May 21, 2016

I think a lot of pilots have this issue. I accepted the 6-8' yoyo effect with no stick input as normal SOP on my P4 from the beginning. However mine has increased to 40-60' now. It's shipping to Dji tomorrow, I just got my rma#. I think they have a bad barometer vendor, that's got to be the issue.

Erised · May 21, 2016

My P4 doesn't drop in a hover, only when I'm flying and let go of the sticks it stops and drops 4 feet and more and then remains very stable. When moving slow around the yard and stop there is no drop. You may have a problem with barometer or the verticle sensors.

ftttu · May 21, 2016

Mine is rock solid also. Only is strong wind will you see any movement. I'd say something to do with your barometer and/or the sonar side.

r62ewa · May 21, 2016

Ever since I've had this Phantom even at 100' altitude the VPS sensor would often show a number as if it was sensing the ground.

John Locke · May 22, 2016

Erised said:
My P4 doesn't drop in a hover, only when I'm flying and let go of the sticks it stops and drops 4 feet and more and then remains very stable. When moving slow around the yard and stop there is no drop. You may have a problem with barometer or the verticle sensors.

Yes I agree it's barometer related, you too likely have the same issue but to a smaller degree. I think DJI went cheap on the accuracy and quality of their barometer. P3 HAS NO SIGN of these up and down yoyo effects. I've never heard any complaints in a year in this forum about P3 doing this, yet many have the 6-8' yoyo effect with P4 when stopping. How can that be explained other than a crappy barometer? Could it be the fan inside playing havoc with the barometer sensor?

I should have named my P4 Duncan.

tcope · May 22, 2016

VPS does not show accurate altitude when you are higher then 10 feet.

BengalBoy · May 22, 2016

Here is a video I took today of my second Phantom 4 doing the "Altitude Yo-Yo"... First one did the same thing..

Stevie_UK · May 22, 2016

Calibrate the RC too? Otherwise looks like faulty barometer. What's it like when not over water? At the end of the vid the visual positioning seems to hold it better. Odd u got this on 2 birds :/ nice location btw

BengalBoy · May 22, 2016

Yes, RC calibrated as well. Flys the same over land or water and really, at 200-300 feet would it even matter? At the end of the video is after I have nudged the sticks a few times, up/down, right/left, etc... If you play around with it for a bit keeping it at a certain altitude and position,, it will eventually hold position. What upsets it is if you fly off full throttle and then take your hands off the sticks. That's what begins the Yo-Yo effect.

John Locke · May 22, 2016

I just shipped my P4 to DJI for this yoyo issue along with doing only 15mph top speed in P mode with OA enabled. Mine has yoyo'd 6 to 8' upon stopping since I got it March 18. However a few weeks ago this yoyo grew to 40 to 60', and doesn't happen right when I stop anymore. I could be hovering for 15 to 30 seconds, then all of a sudden it drops 40' to 60', then it goes back up where it started. This happens with the stock P4 RC and with an Inspire RC that I have. It's pretty strange but I'm confident it will get fixed.

WetDog · May 22, 2016

John Locke said:
Yes I agree it's barometer related, you too likely have the same issue but to a smaller degree. I think DJI went cheap on the accuracy and quality of their barometer. P3 HAS NO SIGN of these up and down yoyo effects. I've never heard any complaints in a year in this forum about P3 doing this, yet many have the 6-8' yoyo effect with P4 when stopping. How can that be explained other than a crappy barometer? Could it be the fan inside playing havoc with the barometer sensor?

I should have named my P4 Duncan.

Although a barometer is certainly possible it doesn't need to be that. For one, if it were a bad batch of barometers, one might expect it to cause variation in both positive and negative altitude. It could also be the firmware attached to the barometer / VPS - perhaps it is picking up or integrating the signal incorrectly. Could be another chip. Could be the VPS system. Could be an interaction between the twin GPS units. It's a very complicated system - lots of ways it can screw up.

Murphy was an optimist.

robinb · May 22, 2016

Phantomix said:
I dont think an IMU calibration would fix it. the IMU is for horizontal movement, not vertical, but im not 100% sure. You may as well try though... I would suggest trying it somewhere else, and was there much wind?

IMU is the vertical movement. Also measures sideways forces etc.
GPS is horizontal position.

Could be VPS is active and having problems with reading the surface texture.

Do an IMU calibration from cold an a flat surface indoors.

BengalBoy · May 22, 2016

IMU calibrations don't solve the issue. I think I'd rather have bamboo jammed under my thumbs than to read one more comment about this issue that starts with "Do IMU calibration...." Chances are, if your on this forum,, your a Geek and have been flyiing Phantoms for awhile unless indicated otherwise.... i.e.,, "Hey, I just got my new Phantom 4 and I don't know much about flying a drone...."

r62ewa · May 22, 2016

Tried mine again today and it is still yo-yoing the 6-8' when hovering. It also usually does 15 mph or so in pmode with OA enabled. Also, when using ActiveTrack it is constantly sensing and avoiding obstacles when there are none to avoid. These issues coupled with my latest No Image Transmission Signal yesterday now puts me in a sour mood after flying as opposed to a good one, very disappointing. Wish I had bought from Apple.

WetDog · May 22, 2016

One thing you could try to get some data is to either download the txt file and analyze it or just turn on the on screen telemetry (I'm spazzing on the actual term - where you create an .SRT file that has the GPS and barometer data on it). See if the barometer is going wonky or if there is something else doing it.

I guess you can't shut off VPS on a P4. You could tape the sensors....

BengalBoy · May 27, 2016

My Altitude Yo-Yo was caused by the carbon fiber gimbal/camera guard I was using. Results from my testing can be seen in this video.

John Locke · May 27, 2016

BengalBoy said:
My Altitude Yo-Yo was caused by the carbon fiber gimbal/camera guard I was using. Results from my testing can be seen in this video.

Bingo, I had a camera guard on mine too. It wasn't carbon fiber but it was positioned just like my P3 carbon fiber camera guard. I never thought the camera guard would do that since everyone uses them on P3s, but the sensors on P4 are different, as they work up to 30' high, and P3 sensors will only work up to 9' high. Since the P4 sensors are different technology, that may be the reason.

I wish I had thought of that before I sent my craft into DJI so I could have tested it. However, I had other issues I wanted fixed, such as my top speed of only 13-15mph in P mode with OA enabled. It's suppose to do 22mph. I've never had it over 19mph, that that was flying with the wind. The other issue was spontaneous total control signal lost at 3000 and 4000' distances when flying over the ocean. This happens regularly, sometimes initiating RTH, and with my P3P this never happens at the same locations, I can go a couple miles with my P3 easily, and then I lose video first, not control signal. My Inspire RC has much better signal integrity when paired with my P4, no complaints with that setup.