After the P4 is switched on, the DJI GO app show a warning that the IMU is initializing - do not move. It takes about 10 seconds and then disappears. What is the P4 actually doing during this time? Is it really important to avoid moving the drone during this initialization?
P4 IMU initialisation
- Thread starter KykPhantom
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Hello,
I just bought my P4 and so far i've booted it several times around the house but no real flight, i was getting IMU is initializing several times when powering the drone on i waited minutes and kept staying like that, had to switch it off and on until finally it disappeared. What exactly is a cold IMU calibration, anyone else had this?
I just bought my P4 and so far i've booted it several times around the house but no real flight, i was getting IMU is initializing several times when powering the drone on i waited minutes and kept staying like that, had to switch it off and on until finally it disappeared. What exactly is a cold IMU calibration, anyone else had this?
The IMU is the inertia measurement unit. It's basically what tells the craft if it's level, how it's tilted, and also measures G forces to measure movements of the craft. I'm not sure why, but there is a warm up process for this unit to work correctly. The IMU must warm up to the point that the last calibration was done at before you can fly. What most pilots do to minimize this warm up time is to fool the IMU during calibration and cool down the craft before starting a calibration. The CPU records that temperature during the calibration. Then, when you start the craft to fly, during the warm up period the IMU only has to warm up to the point that is was initially calibrated at, adequate to fly. That's the only reason to do a "cold IMU calibration", it shortens warm up time when you fly.
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That's not even a thing with the P4, it was a "maybe" thing back in the day with some Inspire's even then, I doubt it.
On top of it, that's not even what he's asking, it's like saying some other completely not related sentence, you might as well have said the weather in Nome AK, that would have been closer
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The reason it warms up a little has to do with the barometer and how it measures pressure, and we all know pressure changes with temp, so it wants to get closer to its operating temp, it lets me do the compass calibration, so I usually do that while its warming up
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During the startup process the IMU provides the drone a reference to being level, based on the most recent IMU calibration when you leveled it. The start up process determines how to level the gimbal (among other things) based on the IMU calibration reference. If you move it around during the start up process, that could affect the initialization process, potentially affecting the leveling of the gimbal accuracy, and other things. I believe that's why.
Well, there went your credibility.
Seriously, if you are unaware of the correlation between the aircraft temperature at the time of the last IMU calibration, and the time it takes for it to be flight-ready after turning it on, you are way behind the times.
Computers run differently at different temps, electronics is affected and your P4 is a lot more advanced than it looks on the outside. There's a lot going on!
Ever left your phone in the glovebox overnight in winter? Not as noticeable these days but older phones show it as they were already slow.. Even the display update will be slow.
Allowing the craft to warm up would suggest that we would get more steady readings, and that all the systems internally would also be in sync and less erratic. I don't move her while warming up.
I did my IMU calibration on a level surface at work.
I do compass dance every time I take the bird out to fly, even if the same place as last time I flew. Personally I'd not advise doing the compass calibration while it's still 'warming up'.
But then I'm a relative newbie to drones, so if anyone wants to give me better advice, please do
Ever left your phone in the glovebox overnight in winter? Not as noticeable these days but older phones show it as they were already slow.. Even the display update will be slow.
Allowing the craft to warm up would suggest that we would get more steady readings, and that all the systems internally would also be in sync and less erratic. I don't move her while warming up.
I did my IMU calibration on a level surface at work.
I do compass dance every time I take the bird out to fly, even if the same place as last time I flew. Personally I'd not advise doing the compass calibration while it's still 'warming up'.
But then I'm a relative newbie to drones, so if anyone wants to give me better advice, please do
It's not a good idea to do a compass calibration every time you take the bird out to fly. There's no need for it unless:
1. You are more than 100mi from the last calibration
2. You have loaded new firmware.
3. You are getting a compass error message
4. The compass sensor bars in Go are not green (ie yellow or red).
Although there has been some mis-information from DJI themselves about this in the past, the consensus in this forum is there is more risk in performaning a calibration every time you fly because you don't know what's around you, buried, or nearby that could give you a bad calibration. Bad calibrations can happen, but the drone doesn't know it until it starts to fly, then things can go whacky. Generally speaking if you get a mid-flight compass error you will be forced into ATTI mode. If you know how to fly ATTI competently, you should be OK. But if your are out of VLOS and flying FPV and don't know the area, you may have navigation problems finding home, but the radar screen and map should suffice. RTH won't work if you have a compass error, the drone will be "lost in air-space".
Many times you'll want to take off from places that are not ideal for compass calibrations, so doing your calibration in an open field with nothing metal nearby and leaving that calibration alone is the best practice, until you encounter one of the 4 circumstances above.
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100 miles? I travel to sisters house sometimes for family deals and they want me to bring it, it's only 2 miles away but if I move I calibrate. But I fly from same spot 97% of the time and don't recal everytime, I used too
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