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Is it normal for altiude & distance to vary?
874 11 2016-8-11
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FlyingCircles
lvl.4
Flight distance : 76309 ft
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I have been attempting to do a perfect calibration of the IMU.  I have tried different conditions like location, temperature, etc.  However I am still getting variation in the distance from the home point once it has been set.

I.E.-  I set the home point then fly away and come right back to same spot but the distance is off by 5-6 feet.  Is this within tolerance or am I doing something wrong during IMU calibration?

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mjlstudios
First Officer
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How do you know you are landing on the exact same spot you took off from?
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DJI-Ken
DJI team
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An IMU calibration probably is not going to make your distance more accurate but it could make a tiny difference.
I would let the aircraft sit for a few minutes and acquire as many satellites as possible then go fly around and come back to the same spot. And if the distance in the app shows 5ft difference, it's not a big deal.
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FlyingCircles
lvl.4
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mjlstudios Posted at 2016-8-11 23:27
How do you know you are landing on the exact same spot you took off from?

You're kidding me right?  I stand five feet away on the driveway with the P3P setting on a point marked with an 'X'.  I increase altitude and fly to some lateral distance away.  Then I maneuver my drone back to the same 'X' that is five feet away from where I am standing.   
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FlyingCircles
lvl.4
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DJI-Ken Posted at 2016-8-11 23:33
An IMU calibration probably is not going to make your distance more accurate but it could make a tin ...

Could a big change in the ambient temperature from the time I did an IMU calibration to the test flight have an effect on the altitude?
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DJI-Ken
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FlyingCircles Posted at 2016-8-12 01:27
Could a big change in the ambient temperature from the time I did an IMU calibration to the test f ...

No, but if you go from a hot to cold or cold to hot condition you need to let the aircraft sit for minutes at the ambient temperature.
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billwish76
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i have a p3s but the p3p has beter gps.. iv heard of this happening more when ppl do a cold imu cal. where they chill the bird in front of a/c or fridge to get warm up time down they say.. i tryed it but the first flight she wondered around more than i like
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DJI-Ken
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billwish76 Posted at 2016-8-12 01:35
i have a p3s but the p3p has beter gps.. iv heard of this happening more when ppl do a cold imu cal. ...

I do a cold IMU calibration as well, make s the "Aircraft Warming up" only take a few seconds. But when you go flying you should let the aircraft sit on the ground for several minutes to get to ambient temperature it your go from inside to outside quickly.
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mjlstudios
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FlyingCircles Posted at 2016-8-11 13:23
You're kidding me right?  I stand five feet away on the driveway with the P3P setting on a point m ...

NO I'M NOT KIDDING YOU! If you are using the RTH function, it is used as an emergency protocol, it will bring the A/C back to you and land safely within 1 to 3 meters from the take off point. It is good practice to ensure that there is  plenty of room around your home point.
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labroides
Captain
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First ... The IMU has nothing to do with distance measuring and will have no effect.
Distance measuring comes from GPS which is unrelated.
2nd .. the inaccuracy you are observing is consistent with the accuracy of consumer GPS.
Sometimes it will be a little closer and sometimes a little further out.
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kcmusa
lvl.2
Flight distance : 132067 ft
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I have turned on the bird and watched the home point move as the GPS gets a better lock. let it sit a min and you can watch the location get closer and more accurate as you wait.
I did this with the Litchi app.
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djordan2
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labroides@yahoo Posted at 2016-8-12 22:21
First ... The IMU has nothing to do with distance measuring and will have no effect.
Distance measur ...

Right you are!  Consumer GPS is accurate to within about 5 feet, sometimes more.  If you want better, you need aviation or military GPS.  In general aviation a GPS approach to a runway is actuate to within something like an inch.  Maybe less, I just don't remember now.
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