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[Kilrah]

Also forgot to mention it also shows I never altered altitude via sticks on the way out to where it does a 360 and then drops altitude. Did you say there was evidence of manual altitude adjustment on the way out. If so can you give me any indication of where that occurred please.

It is still not clear which file is the crash file. One shows adjustments and the other doesn't.

5ft seem to be a great deal of altitude loss?

Not at all. Due to how the technology works you should expect height to potentially deviate easily 30ft either way. And again that particular situation is just asking for it to go off track.
Precise height can be held only when the ground below is close (specs say 11m aka ~30ft) and not changing height too much like here.

I have seen many Youtube videos of the Mavic 2 in similar situations and i can't remember them dropping height by around 5ft.

Real life isn't perfect. Sometimes it will be super precise, sometimes it won't. Need to expect the worst and be ready for when it doesn't.

its a £1300 drone not £100.

That makes no difference at all. Tech is what it is. Actually in this case the £100 drone could have done better... the M2 has advanced sensors that will improve behavior in some scenarios, but can potentially reduce accuracy in others like yours. Again you need to understand function correctly when you get that close to tolerances.

i was stood on the embankment and the bricks of the old reservoir actually made it difficult to see an height fluctuation.

It is subjective to say keep an eye on the drone and not the screen, i'm sure there are thousands of people out there who have flown their drone kilometres with only camera view?

That's why I pointed that out, the height variation was VERY obvious watching your video.

The whole idea of the flight was to prove nothing was working as expected.

I actually do not see anything that doesn't work as expected in the video posted in this thread...

Just as a point of interest where does it state in the manual that the drone is capable of losing altitude because i must of missed that.

It's important to read the manual but it won't go to depth explaining the technology and all good piloting practices. You don't learn to drive a car (or fly an aircraft, which this is) just by reading its manual.

 

[BudWalker]

Sorry BudWalker i have been thanking Sar104,.....

Sorry BudWalker i have been thanking Sar when its you who has been looking at the log. ......

Regards

That's OK, I've been called worse.

 

[Newton Heath]

It isn't that you missed anything in the manual about it changing altitude, it's that you missed noting that the manual doesn't promise that it won't. A couple of meters variation is neither uncommon nor unexpected for an aircraft that has a barometric sensor as its primary absolute altitude measurement.

Thank you Sar104 for your response it much appreciated, but i still feel aggrieved given i had legitimate claims to return the unit given issues i reported. £500 is a lot of money as a quote, when the leg only costs £25 and they are claiming issues with the camera which i had previously reported amongst other things and is proven in the flight log and submitted video. I just hope they play fair and offer a repair where at worst i just have to pay for the replacement leg. By the way when i sent in the drone, they also quoted for the back leg which had nothing more than an abrasion on it, which ironically it never had it on when posted back. in fact it did not have a mark on it, not even the front buckled leg had a mark as it hit grass.

 

[ac0j]

Being on the pointy hill didn’t help the barometric sensor either.

 

[sar104]

Thank you Sar104 for your response it much appreciated, but i still feel aggrieved given i had legitimate claims to return the unit given issues i reported. £500 is a lot of money as a quote, when the leg only costs £25 and they are claiming issues with the camera which i had previously reported amongst other things and is proven in the flight log and submitted video. I just hope they play fair and offer a repair where at worst i just have to pay for the replacement leg. By the way when i sent in the drone, they also quoted for the back leg which had nothing more than an abrasion on it, which ironically it never had it on when posted back. in fact it did not have a mark on it, not even the front buckled leg had a mark as it hit grass.

That's understandable, and it's unfortunate that it crashed before you sent it back. It may still be worth arguing the point with them regarding the camera/gimbal issue.

 

[Newton Heath]

It is still not clear which file is the crash file. One shows adjustments and the other doesn't.


Not at all. Due to how the technology works you should expect height to potentially deviate easily 30ft either way. And again that particular situation is just asking for it to go off track.
Precise height can be held only when the ground below is close (specs say 11m aka ~30ft) and not changing height too much like here.

Real life isn't perfect. Sometimes it will be super precise, sometimes it won't. Need to expect the worst and be ready for when it doesn't.


That makes no difference at all. Tech is what it is. Actually in this case the £100 drone could have done better... the M2 has advanced sensors that will improve behavior in some scenarios, but can potentially reduce accuracy in others like yours. Again you need to understand function correctly when you get that close to tolerances.



That's why I pointed that out, the height variation was VERY obvious watching your video.


I actually do not see anything that doesn't work as expected in the video posted in this thread...


It's important to read the manual but it won't go to depth explaining the technology and all good piloting practices. You don't learn to drive a car (or fly an aircraft, which this is) just by reading its manual.

Thanks for your response, it is obvious you know much about this drone which i respect, i read the part on the website about the 30ft. The ironic part is i took the unit to that area because there is a prison nearby and it was away from buildings and built up areas etc. Prior to this flight i took it to another location with a lot of trees and a deep valley and it kept it's course and altitude perfectly it just had bad skipping on the video in point of interest mode and when i took it to the next location the camera flipped out and gave a Gimbal overload warning which was in the flight log i posted. A brand new drone should not be flipping out and giving an overload message.

 

[DanMan32]

30ft height drift without an external trigger sounds excessive expectations to me. Even 5ft drift seems borderline.

 

[BJR981S]

30ft height drift without an external trigger sounds excessive expectations to me. Even 5ft drift seems borderline.

I think that 30 feet is where the optical sensor priorities over the barometer. On a grassy embankment the Optical sensor is unlikely to be able to determine the reduction in altitude reliably.

I suspect that there is all some bugs in the M2 Optical sensors that are not yet fixed. Hence the precision landing feature not enabled.

 

[laurens23]

I think that 30 feet is where the optical sensor priorities over the barometer.

The optical sensor is only for increasing positional accuracy, (ie. to supplement the GPS, not the barometer)
The ultrasonic sensor measures the altitude when below ~30ft, but is NOT used to keep altitude.
Otherwise the drone would climb and descend with the terrain when below 30ft it does not do this.

The drone always uses the barometric sensor for altitude. the ultrasonic sensor is to detect the ground when landing.

 

[BJR981S]

The optical sensor is only for increasing positional accuracy, (ie. to supplement the GPS, not the barometer)
The ultrasonic sensor measures the altitude when below ~30ft, but is NOT used to keep altitude.
Otherwise the drone would climb and descend with the terrain when below 30ft it does not do this.

The drone always uses the barometric sensor for altitude. the ultrasonic sensor is to detect the ground when landing.

Not correct. You make too many false assumptions.

Watch this video.

Pay attention to the referenced video in this video of altitude wandering over water due to the Optical sensor.

Also pay attention to the DJI Reference material used in the video where DJI recommends to disable the Vision System to prevent altitude fluctuations.

Also read this section posted below from the DJI manual on the vision system. The highlighted text would not be required if your assumptions were correct.

The performance of the Forward and Downward Vision Systems are affected by the surface beingflown over. Ultrasonic sensors may not be able to accurately measure distances when operatingabove sound-absorbing materials and the camera may not function correctly in suboptimal environments. The aircraft will switch from P-mode to Atti mode automatically if neither GPS nor Forward and Downward Vision Systems are available. Operate the aircraft with great caution in the following situations:
Flying over monochrome surfaces (e.g. pure black, pure white, pure red, pure green). Flying over a highly reflective surfaces.
Flying at high speeds of over 22mph (36kph) at 2 meters or over 11mph (18kph) 1 meter.Flying over water or transparent surfaces.
Flying over moving surfaces or objects.
Flying over inclined surfaces that will deflect sound waves away from the aircraft. Flying over small and fine objects (e.g. tree branches and power lines).
Flying in an area where the lighting changes frequently or drastically.
Flying over extremely dark (lux < 10) or bright (lux > 100,000) surfaces.
Flying over surfaces that can absorb sound waves (e.g. thick carpet).
Flying over surfaces without clear patterns or texture.
Flying over surfaces with identical repeating patterns or textures (e.g. tiling).
Keep sensors clean at all times. Dirt or other debris may adversely affect their effectiveness. The Downward Vision System is only effective when the aircraft is at altitudes of 0.3 to 13 meters.Forward and Downward Vision Systems may not function properly when the aircraft is flyingover water.
The Forward and Downward Vision System may not be able to recognize patterns on the ground in low light (less than 100lux).
Do not use other ultrasonic devices with a frequency of 40KHz when Forward and DownwardVision Systems are in operation.

 

[sar104]

Not correct. You make too many false assumptions.

Watch this video.

Pay attention to the referenced video in this video of altitude wandering over water due to the Optical sensor.

Also pay attention to the DJI Reference material used in the video where DJI recommends to disable the Vision System to prevent altitude fluctuations.

Also read this section posted below from the DJI manual on the vision system. The highlighted text would not be required if your assumptions were correct.

The performance of the Forward and Downward Vision Systems are affected by the surface beingflown over. Ultrasonic sensors may not be able to accurately measure distances when operatingabove sound-absorbing materials and the camera may not function correctly in suboptimal environments. The aircraft will switch from P-mode to Atti mode automatically if neither GPS nor Forward and Downward Vision Systems are available. Operate the aircraft with great caution in the following situations:
Flying over monochrome surfaces (e.g. pure black, pure white, pure red, pure green). Flying over a highly reflective surfaces.
Flying at high speeds of over 22mph (36kph) at 2 meters or over 11mph (18kph) 1 meter.Flying over water or transparent surfaces.
Flying over moving surfaces or objects.
Flying over inclined surfaces that will deflect sound waves away from the aircraft. Flying over small and fine objects (e.g. tree branches and power lines).
Flying in an area where the lighting changes frequently or drastically.
Flying over extremely dark (lux < 10) or bright (lux > 100,000) surfaces.
Flying over surfaces that can absorb sound waves (e.g. thick carpet).
Flying over surfaces without clear patterns or texture.
Flying over surfaces with identical repeating patterns or textures (e.g. tiling).
Keep sensors clean at all times. Dirt or other debris may adversely affect their effectiveness. The Downward Vision System is only effective when the aircraft is at altitudes of 0.3 to 13 meters.Forward and Downward Vision Systems may not function properly when the aircraft is flyingover water.
The Forward and Downward Vision System may not be able to recognize patterns on the ground in low light (less than 100lux).
Do not use other ultrasonic devices with a frequency of 40KHz when Forward and DownwardVision Systems are in operation.

But neither that statement, nor any of the others on the vision system, imply that the ultrasonic height measurement system is used to maintain altitude in flight. It cannot do that, because constant altitude while flying means does not mean constant altitude AGL. The ultrasonic height measurement on the Mavic Pro is used to maintain position during hover when, at least over solid ground, the altitude AGL is expected to remain constant.

 

[BJR981S]

But neither that statement, nor any of the others on the vision system, imply that the ultrasonic height measurement system is used to maintain altitude in flight. It cannot do that, because constant altitude while flying means does not mean constant altitude AGL. The ultrasonic height measurement on the Mavic Pro is used to maintain position during hover when, at least over solid ground, the altitude AGL is expected to remain constant.

The quoted text was for the sake of the post I responded to where he claimed "it was for landing" only. And the text clearly states flying. Not landing. The specific highlight is for the OP complaint that he ran into the bank and expected obstacle avoidance to prevent the collision. It would not matter if it was sideways or forward as was previous suggested.

Please watch the video link I posted and DJIs response on disabling the vision system to prevent altitude wandering over water. This only occurs when the vision system has priority over the barometer for altitude. The real world demonstration confirms this as the Barometer does not care about what surface its flying over.

Watch the video and then reply again if you want further clarification.

Cheers

 

[sar104]

The quoted text was for the sake of the post I responded to where he claimed "it was for landing" only. And the text clearly states flying. Not landing. The specific highlight is for the OP complaint that he ran into the bank and expected obstacle avoidance to prevent the collision. It would not matter if it was sideways or forward as was previous suggested.

Please watch the video link I posted and DJIs response on disabling the vision system to prevent altitude wandering over water. This only occurs when the vision system has priority over the barometer for altitude. The real world demonstration confirms this as the Barometer does not care about what surface its flying over.

Watch the video and then reply again if you want further clarification.

Cheers

Not wished to drag this out, but the post that you responded to with the statement "Not correct", was:

The optical sensor is only for increasing positional accuracy, (ie. to supplement the GPS, not the barometer)​

The ultrasonic sensor measures the altitude when below ~30ft, but is NOT used to keep altitude.​

Otherwise the drone would climb and descend with the terrain when below 30ft it does not do this.​

​

The drone always uses the barometric sensor for altitude. the ultrasonic sensor is to detect the ground when landing.​

Those statements are correct. The Mavic 1 uses the ultrasonic sensor to measure height when close to the ground and for landing, but it does not use it in normal flight to control altitude. FYI the Mavic 2, under discussion here, doesn't even have an ultrasonic sensor.

Maybe I've simply lost track of the point that you are trying to make.

 

[BJR981S]

But neither that statement, nor any of the others on the vision system, imply that the ultrasonic height measurement system is used to maintain altitude in flight. It cannot do that, because constant altitude while flying means does not mean constant altitude AGL. The ultrasonic height measurement on the Mavic Pro is used to maintain position during hover when, at least over solid ground, the altitude AGL is expected to remain constant.

Ah, I have read your statement a number of times now. I think I see the conflict in definitions.

My flying definition on this subject relates to hover or low speed flight and / or Flight mode selection. I should have specified this in the first place.

My definition of Barometer being Overridden by the Vision system is: Landing, Hovering, or minimum speed adjustments, Terrain Follow, and Tripod Mode (yet to be confirmed by me) all only within the Vison system parameters 1 to 13 Metres AGL. As defined in the terrain follow enablement parameters.

From the Pro manual.

The Downward Vision System is utilized in Terrain Follow Mode to maintain a height above ground between 1 and 13 meters. This mode is designed for use on grassland sloped at no more than 20°.
Enable the Terrain Follow Mode by tapping the Intelligent Flight Mode icon in the DJI GO 4 app. When this mode is enabled, the aircraft’s current height will be recorded. The aircraft will maintain the recorded heightduring flight and ascend when the slope rises. However, the aircraft will not descend in downward slopes.

I need to investigate the downward slopes some more. I don't know if it refers to descending below the preset height as an absolute or descending from above the preset height to the min of the preset height.

e.g. Flying up a slope and then returning. Does it return and descend to the preset altitude or return at the max altitude it reaches. In the later case it can fall out of the scope of the 13 Metre range. And in the first case it can also fall out if it travels over a valley.

Have you tried this yourself?

 

[BJR981S]

Not wished to drag this out, but the post that you responded to with the statement "Not correct", was:

The optical sensor is only for increasing positional accuracy, (ie. to supplement the GPS, not the barometer)​

The ultrasonic sensor measures the altitude when below ~30ft, but is NOT used to keep altitude.​

Otherwise the drone would climb and descend with the terrain when below 30ft it does not do this.​

​

The drone always uses the barometric sensor for altitude. the ultrasonic sensor is to detect the ground when landing.​

Those statements are correct. The Mavic 1 uses the ultrasonic sensor to measure height when close to the ground and for landing, but it does not use it in normal flight to control altitude. FYI the Mavic 2, under discussion here, doesn't even have an ultrasonic sensor.

Maybe I've simply lost track of the point that you are trying to make.

Just a misunderstanding of definitions I believe.

The Mavic 2 has demonstrated a number of issues with the downward vision system. I suspect in the M2 space that there are some bugs in the FW / HW that they are yet to resolve. Hence the no precision landing feature availability.

Please watch the video and the DJI reply. The Vison system is operational and controls altitude in a hover as demonstrated in the video.

This is why you get greater accuracy of altitude stability when below 13 Metres than you do above. This is how you get the increased precision indoors in particular and outdoors than the specified accuracy of the Barometer and GPS system.

The real point that I try and get across is that the automation is complex, well misunderstood and at some stage will let you down. Everyone should learn how to fly first and not rely on the automation.

Cheers.

 

[mrgrind]

I would have been much closer to the drone while testing it, even in the frame if needs be. Not trying to capture footage from a distance.
Good luck

 

[sar104]

Ah, I have read your statement a number of times now. I think I see the conflict in definitions.

My flying definition on this subject relates to hover or low speed flight and / or Flight mode selection. I should have specified this in the first place.

My definition of Barometer being Overridden by the Vision system is: Landing, Hovering, or minimum speed adjustments, Terrain Follow, and Tripod Mode (yet to be confirmed by me) all only within the Vison system parameters 1 to 13 Metres AGL. As defined in the terrain follow enablement parameters.

From the Pro manual.

The Downward Vision System is utilized in Terrain Follow Mode to maintain a height above ground between 1 and 13 meters. This mode is designed for use on grassland sloped at no more than 20°.
Enable the Terrain Follow Mode by tapping the Intelligent Flight Mode icon in the DJI GO 4 app. When this mode is enabled, the aircraft’s current height will be recorded. The aircraft will maintain the recorded heightduring flight and ascend when the slope rises. However, the aircraft will not descend in downward slopes.

I need to investigate the downward slopes some more. I don't know if it refers to descending below the preset height as an absolute or descending from above the preset height to the min of the preset height.

e.g. Flying up a slope and then returning. Does it return and descend to the preset altitude or return at the max altitude it reaches. In the later case it can fall out of the scope of the 13 Metre range. And in the first case it can also fall out if it travels over a valley.

Have you tried this yourself?

Flying up a slope requires the application of positive throttle to ascend as you go. Flying back down the slope similarly requires negative throttle, otherwise the aircraft will hold altitude, barometrically, relative to the takeoff point. There is no Mavic flight mode that follows the terrain via ultrasonic height measurement. Terrain following will use DEMs. One day, not doubt, it will be able to follow terrain via its vision system, but I doubt we will see that for a while.

 

[sar104]

Just a misunderstanding of definitions I believe.

The Mavic 2 has demonstrated a number of issues with the downward vision system. I suspect in the M2 space that there are some bugs in the FW / HW that they are yet to resolve. Hence the no precision landing feature availability.

Please watch the video and the DJI reply. The Vison system is operational and controls altitude in a hover as demonstrated in the video.

This is why you get greater accuracy of altitude stability when below 13 Metres than you do above. This is how you get the increased precision indoors in particular and outdoors than the specified accuracy of the Barometer and GPS system.

The real point that I try and get across is that the automation is complex, well misunderstood and at some stage will let you down. Everyone should learn how to fly first and not rely on the automation.

Cheers.

Yes - agreed on those points, and definitely on that conclusion.