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question about flying over concrete path

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Mar 16, 2019
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9
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54
Hi, i was trying to fly my spark along a path lined each side with smallish trees that formed a canopy, i found it erratic esp with flying higher or lower without me adjusting height, the same with obstacle avoidance on or off, im guessing the path may have have to little detail? or maybe steal in the concrete, i was trying to fly about 2 metres above the ground, thoughts
 
it could be because of bottom sensors. If the path was smooth and kinda single-colored, the sensors (they are also used for stabilization when aircraft is flying low) might get confused and having a hard time keeping the drone steady especially if it was in low light conditions. Also concrete might have some metallic rebar in it so the compass interference might come in account too (but that's usually reported by red error on top bar of app).
 
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Hi, i was trying to fly my spark along a path lined each side with smallish trees that formed a canopy, i found it erratic esp with flying higher or lower without me adjusting height, the same with obstacle avoidance on or off, im guessing the path may have have to little detail? or maybe steal in the concrete, i was trying to fly about 2 metres above the ground, thoughts

You may be experiencing a well known copter blade phenomenon known as "ground effect". The flight behavior of a quadcopter becomes unstable at extremely low altitudes because it's own propwash bounces off the ground below and creates turbulent air.

With sufficient altitude this effect completely disappears because there is room for the turbulent air to disperse. It's very noticeable at 2 feet but at 2 metres not so much.

An imperceptible breeze could also push the drone off course and yet be unnoticeable to a operator just a few metres away. You can figure out if it's wind by the direction it's pushed when you fly the straight line course in the opposite direction. Those are usually side to side course deviations.

Unbalanced or damaged props are also a common reason for erratic flight paths. Check your blades with eyes and fingers for cracks and nicks. Swap the props to different motors to balance any subtle warping.

My drones don't all fly perfectly straight line -- I've had to accept that. They're just not all that precise out of the box and become less so over time.

But the up/down drift you see when really close above a hard surface is ground effect -- darn physics again!
 
Always tells me to calibrate the Imu until I move away from the concrete. Happens in many locations with concrete nearby.

That is the rebar inside.
With a Spark I just take off and hover for a few seconds.
Always seems to self fix.
But with my Mavic Air, locks me out of takeoff and have to re-calibrate successfully or reboot the system.
 
Always tells me to calibrate the Imu until I move away from the concrete. Happens in many locations with concrete nearby.


Try the hand launch method.

Set the Spark on the ground to establish the Home Point (unless you want to hold it level in your hand while gathering the HP information) and launch from your hand either by the double tap trick that works for some, or use the auto launch swipe icon on the main page.

You can also program one of the Fn button(s) to auto launch the Spark.

Be careful when using this feature as fumbling with the RC may inadvertently launch the Spark if one of the buttons are pushed during the setup of flight.
 
You may be experiencing a well known copter blade phenomenon known as "ground effect". The flight behavior of a quadcopter becomes unstable at extremely low altitudes because it's own propwash bounces off the ground below and creates turbulent air.

With sufficient altitude this effect completely disappears because there is room for the turbulent air to disperse. It's very noticeable at 2 feet but at 2 metres not so much.

An imperceptible breeze could also push the drone off course and yet be unnoticeable to a operator just a few metres away. You can figure out if it's wind by the direction it's pushed when you fly the straight line course in the opposite direction. Those are usually side to side course deviations.

Unbalanced or damaged props are also a common reason for erratic flight paths. Check your blades with eyes and fingers for cracks and nicks. Swap the props to different motors to balance any subtle warping.

My drones don't all fly perfectly straight line -- I've had to accept that. They're just not all that precise out of the box and become less so over time.

But the up/down drift you see when really close above a hard surface is ground effect -- darn physics again!

oh didnt think of that, you could be right and some great tips
 
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yep maybe where are how i wanted to film just wont work shame as it looked cool while it was level

Now that we've established your aircraft is not malfunctioning...

Here's another method to capture that particular footage that I have used in that scenario. It's a total cheat but gets near perfect results and most people don't think of it...

example: You were trying to fly through a narrow tunnel of trees just a few feet of the ground but drone wouldn't reliably follow your commands and gave erratic footage

Try this: Use the Spark as a hand held video camera that has a gimbal-stabilized image. Just power on AC on as usual but instead of flying it just hold it and walk the exact flight path at the desired height. You need to walk a bit funny to eliminate slight up and down with each step but you'll figure that out in a minute.

9992

If you use that technique often there are inexpensive mounts that make it easier and also hold your monitor in view. In that case I remove props for safety. If you are are a perfectionist there after-effects to smooth it even further. And hyperlapse tools that can get very creative results
 
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The thing I'd add is that a Litchi flight path I did up a drive worked fine until I got to a canopy of trees. It went into atti mode as the GPS was interfered with and behaved badly. If the drone loses GPS because of flying under stuff that might also be relevant.

I do like the hand held bracket idea though!
 
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You may be experiencing a well known copter blade phenomenon known as "ground effect". The flight behavior of a quadcopter becomes unstable at extremely low altitudes because it's own propwash bounces off the ground below and creates turbulent air.

With sufficient altitude this effect completely disappears because there is room for the turbulent air to disperse. It's very noticeable at 2 feet but at 2 metres not so much.

An imperceptible breeze could also push the drone off course and yet be unnoticeable to a operator just a few metres away. You can figure out if it's wind by the direction it's pushed when you fly the straight line course in the opposite direction. Those are usually side to side course deviations.

Unbalanced or damaged props are also a common reason for erratic flight paths. Check your blades with eyes and fingers for cracks and nicks. Swap the props to different motors to balance any subtle warping.

My drones don't all fly perfectly straight line -- I've had to accept that. They're just not all that precise out of the box and become less so over time.

But the up/down drift you see when really close above a hard surface is ground effect -- darn physics again!


Andre, I come to the drone world from the R/C copter world. Do quad copters also suffer from vortex ring state?
 
Andre, I come to the drone world from the R/C copter world. Do quad copters also suffer from vortex ring state?

Yes (and no). Quadcopters are also susceptible to vortex ring state. But DJI consumer drones mitigate the effect with altitude hold and automated controlled descent when landing.

When the Spark is descending the downward facing sensors and altitude input temporarily freeze the descent a few feet from the ground. The aircraft then controls the rate of descent regardless of any additional downward joystick input from the operator.

I strongly suspect this feature was primarily implemented to avoid the inevitable hard landings by newbie pilots rather than VRS. Drones have pretty favorable weight to power ratios which make settling with power less of an issue to begin with.

If this feature wasn't standard the average drone would only last a few flights. VRS should be a non factor and hard landings should be rare when everything is functioning as designed.
 
Yes (and no). Quadcopters are also susceptible to vortex ring state. But DJI consumer drones mitigate the effect with altitude hold and automated controlled descent when landing.

When the Spark is descending the downward facing sensors and altitude input temporarily freeze the descent a few feet from the ground. The aircraft then controls the rate of descent regardless of any additional downward joystick input from the operator.

I strongly suspect this feature was primarily implemented to avoid the inevitable hard landings by newbie pilots rather than VRS. Drones have pretty favorable weight to power ratios which make settling with power less of an issue to begin with.

If this feature wasn't standard the average drone would only last a few flights. VRS should be a non factor and hard landings should be rare when everything is functioning as designed.

I’ll tell you, the Spark is a 100 times easier to fly then the older helicopters. I’ve got got fixed and variable pitch birds that can be a real chore to fly. If you look away for a second things can go sideways quickly. With the Spark you can let go of the sticks and it just hovers oh so beautifully all by itself. It’s a real pleasure I tell ya!
 
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I’ll tell you, the Spark is a 100 times easier to fly then the older helicopters. I’ve got got fixed and variable pitch birds that can be a real chore to fly. If you look away for a second things can go sideways quickly. With the Spark you can let go of the sticks and it just hovers oh so beautifully all by o It’s a real pleasure I tell ya!

GPS is the "secret ingredient" that allows DJI quadcopters to hover without drift. RC helicopters don't have GPS? That's really surprising
 
I have always found flying low to ground or water more erratic than flying well above it. Apart from the 'ground effect' and VPS factors described above, one should also remember that we get a much stronger GPS reception when we are well above the ground and clear of obstacles like trees, buildings. That ensures a more steady hover or straight path according to the stick inputs.
 
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