nixuspix Posted at 2018-6-18 11:22
Is it possible for DJI programmers to decrease instability of the drone, caused by conflict between Compass and GPS (started with multiple YAW errors and resolved nowadays by switching off GPS and entering ATTI mode), by using the hardware of smartphone - its GPS and compass, which most likely are of much better quality and sensitivity, than built in AC

nixuspix,

I disagree with your statement about higher quality compass, GPS and IMU in mobile devices than in Spark.
But perhaps your comment was tongue in cheek :-). Yes, DJI could improve but - we get what we paid for.

Mobile devices do not fly and acquiring GPS signal is helped with quick cashe table downloads from cell towers. It is complicated. IMU and gyroscopes in mobile devices are not even close to sensitivity of these in Spark. How many times you had you phone in vertical position and looked at some photo and then changed its orientation only to see that orientation of photo is stuck and does not change? And it changed after you tried to wiggle it few times? How many times your google maps navigation got stuck for a few seconds or longer while driving? Why do I need to do figure eights in the air with my mobile every so often to re-calibrate its gyro?

We do not notice those issues with mobiles because they do not manifest themselves in such a drastic way as they would manifest themselves in drones. In mobiles they are small annoyances which everybody got used to and accepts as part of the deal. With drones they may mean crash or fly-away pushed by wind.

While I see a lot of issues with Spark, I am impressed with DJI engineering.
Well, I have to add that I am not impressed at all with their support on this forum though :-).

Mirek6 Posted at 2018-6-18 11:20
Dan,

DMX_MT pointed me to you post – thanks DMX_MT since this case is fairly fascinating!

For me Mirek is one of the Best Analyzers here. I Really Love his Opinions !

I post tomorrow as its late here today !

thank you Mirek, very detailed analysys. I agree all except the tilting. Please see the video and then let me know what you think.

DMX_MT Posted at 2018-6-18 12:09
For me Mirek is one of the Best Analyzers here. I Really Love his Opinions !

I post tomorrow as its late here today !

Hey DMX_MT,

I am flattered. But I would be as happy if DJI proved me wrong.
I know they will not (that's my humble me speaking :-)).
Seriously though, it is one continuous learning journey. I learned and still learn a lot from this forum, and I am happy if I can contribute back.

Dan O Posted at 2018-6-18 12:11
thank you Mirek, very detailed analysys. I agree all except the tilting. Please see the video and then let me know what you think.

Dan,

How can I access your video? I do not see any link.
I would be interested in your low resolution video from DJI GO cache.
Perhaps another valuable lesson to learn here?

Did not uploaded, please see it here.

https://youtu.be/EbZ1mpqrKMI

I am sure you will agree with me after you will notice the behavoiur.

@Mirek6

Very good analysis but lacking one thing - mass forum posting of this issue started in April.
Unless DJI changed IMU manufacturers or specs of the IMU, the issue would have "always been" since the beginning.

Or at least 0900 firmware upgrade.
But that was 12/21/2017

Thoughts?

Mirek6 Posted at 2018-6-18 12:08
nixuspix,

I disagree with your statement about higher quality compass, GPS and IMU in mobile devices than in Spark.

I’m in agreement with Mirek with respect to his analysis and conclusions.

Modern gyros and accelerometers while having the appearance of a regular integrated circuit package are still mechanical devices with moving components. While I generally fly my racequads in ACRO mode I can still tune them to flip and roll in ATTI mode. However when the flight controller tries to auto level after such an aggressive manouver the recovery will usually be far less than graceful, putting it mildly. More often than not the quad might remain confused until a hard reset, disconnecting and reconnecting the battery, is done. This isn’t an issue in this case as these machines generally don’t have the added complication of dealing with data from a GPS and digital compass. As well as the Spark I have a couple of Phantoms and a heavy lift hexacopter for aerial imaging. These are speed limited when in GPS mode. However when switched to ATTI mode they can move at quite a pace but they are not subjected to heavy braking forces in the same way that the Spark is when it’s in Sport Mode.

I’m thankful that I haven’t experienced any issues with my Spark though I use it more as an aerial still camera so it hasn’t been flown in Sport Mode, I have my race and collective pitch quads for speedy shenanigans;-), though I still have the fear that the Spark may unexpectedly decide to go rogue when the IMU, compass, and GPS, components have a disagreement with one another.

If Mirek is prepared to stump up for coffee I’ll gladly bring the cookies/biscuits to the party.

I just wish that DJI would either fix all of these problems with the Spark or give us our Money back. They have known about this Yaw issue for months and done NOTHING, they have know about the choppy video, lost connections and GPS issues since day one and done nothing.......... After a year this Spark is nothing but frustration, Thanks DJI for nothing...

Dan O Posted at 2018-6-18 02:05
The wind was close to zero on ground level, as the altitude was 24 meters I suspect no issues over there as well. No high wind messages and 15 min before have flown at 90 meters high in the same area with no issue at all.

I must insist that whatever external factor we may search it's time to accept that this is design issue, either software or hardware.

Since you say this is a design issue, do you know of a drone that is easy to fly in ATTI mode?  One that beginners or first time drone owners can fly without GPS stabilization?  It sounded like the Spark did respond to stick movements but with a video delay to its response (when not flown in VLOS).

I think being able to fly in ATTI mode, or at least keep it near you, is an essential skill for all drone pilots.  Issues as pilots learn to fly better happens with all radio control aircraft (assuming you wrecked your planes and helicopter when learning).

Not a Spark design issue but a learning to pilot quadcopters issue.  Learning to pilot any quadcopter issue.

Nidge Posted at 2018-6-18 13:13
I’m in agreement with Mirek with respect to his analysis and conclusions.

Modern gyros and accelerometers while having the appearance of a regular integrated circuit package are still mechanical devices with moving components. While I generally fly my racequads in ACRO mode I can still tune them to flip and roll in ATTI mode. However when the flight controller tries to auto level after such an aggressive manouver the recovery will usually be far less than graceful, putting it mildly. More often than not the quad might remain confused until a hard reset, disconnecting and reconnecting the battery, is done. This isn’t an issue in this case as these machines generally don’t have the added complication of dealing with data from a GPS and digital compass. As well as the Spark I have a couple of Phantoms and a heavy lift hexacopter for aerial imaging. These are speed limited when in GPS mode. However when switched to ATTI mode they can move at quite a pace but they are not subjected to heavy braking forces in the same way that the Spark is when it’s in Sport Mode.

What do you make of the reports that the Spark does not follow the RC stick movements when in ATTI mode?

It doesn't make sense to me.  I think the newbie pilots are mixed up with their orientation when the Spark is facing them.  Or, they are watching the video, as they fly in ATTI mode, and not compensating for video lag as they bang the sticks around.  The Spark has a lot of lag in the video feed.  Too much for unstabilized (GPS) flying.  Hence the need to keep the drone within VLOS when flown.

I agree largely with Mirek6's analysis of the flight.  Unfortunately, none of us can know for sure what was the reason for the YAW errors, but I have always assumed the same as Mirek6 in regards to something going wrong in the system and causing different sensor systems to provide conflicting data and causing it to drop into ATTI mode.  I also agree that it is very likely that the issue started happening before the Spark's logs actually started indicating there was a problem.  You can see it in the video start to get a bit "slippery" in its movements and not being steady like expected when in full control.

In regards to the "Weak GPS Signal" message at 1:21.5, that is a direct result of the action taken and logged at 1:17.1 where it exited GPS mode and started ignoring all GPS data as far as navigation goes.  I agree with Mirek6's latter thought on this rather than it having anything to do with satellite geo-spacing or anything directly to do with GPS specifically.

Where I do disagree with some of the thoughts expressed in this thread is that although control in ATTI mode is difficult, from my perspective, the Spark responded to all stick inputs from the pilot and gave corresponding movements.  When yaw inputs were given to the sticks, it yawed appropriately.  When roll inputs were given, it rolled appropriately.  I think where a lot of people (even very experienced pilots) misunderstand and think its not responding is because when the Spark is in normal mode, it is like driving a golf cart.  In a golf cart, full throttle is still not that fast and most of the time the top speed is governed to something very slow.  In normal mode (especially with obstacle avoidance turned on), the Spark's speed is severely governed.  However, when it kicks over into ATTI mode, your golf cart immediately transforms into a race car with no brakes.

So in this instance, at 1:04.1, the pilot did a full right stick backwards to move the aircraft backwards at full speed.  While it was in GPS mode, it resulted in a golf cart slow speed.  However, when it flipped to ATTI mode at 1:16.0, the golf cart transformed instantly to the race car with no brakes and accelerated from under 5m/s (under 8mph) to over 16m/s (36mph) in just a few short seconds.  Once the right stick was released, it stopped accelerating and started slightly decreasing its speed until it was flipped into Sport mode and regained its composure and immediately hit the brakes to slow it down.

I'm in no way blaming the pilot for this because it is impossible to react instantaneously.  Just trying to explain the behavior I see.  In spite of the pilot feeling like they have no control, they actually do have way more control than they think.  

In this particular case, it was great thinking by the pilot to flip it into Sports mode so quickly.  This isn't the first time I've seen Sports mode help a pilot get an aircraft back under control.  Not sure it will help in all situations, but in my opinion, definitely something to potentially try when in a bad spot.

Glad you were able to get your Spark back!  I hope DJI can investigate and understand what the root cause was and create a solution to prevent further occurrences!

Dan O Posted at 2018-6-18 12:53
Did not uploaded, please see it here.

Dan,

You are right - your gimbal movements are abnormal. I am not talking about when you are in Sport mode but regular flying. Your gimbal's gyroscope did not work well.

I do not know Spark inner design but I guess it is possible that Spark's gimbal motor is using signals from Sparks IMU gyroscope. If Spark's IMU gyroscope was stuck or malfunctioning - as I think it was - than we have the answer.

Did you try to fly Spark again? If you did, is gimbal behaving in the same bad manner? If it is while Spark is functioning properly, than it is a separate issue. If it is OK and Spark is OK, than chances are it is the same IMU gyroscope which got stuck and unstuck with Spark's movements.

I wanted to know what YAW ERROR is as well.

It is always the caused of Compass Error the followed by GPS Error then ATTI.. .

YAW Error always comes FIRST ~

SparkChog Posted at 2018-6-18 15:55
I wanted to know what YAW ERROR is as well.

It is always the caused of Compass Error the followed by GPS Error then ATTI.. .

Read through this thread...there are links to the issue yet no solution as of this moment.

pmshop Posted at 2018-6-18 16:11
Read through this thread...there are links to the issue yet no solution as of this moment.

There is no exact explanation. That's what i need to know. What causes YAW ERROR and HOW TO PREVENT IT.

SparkChog Posted at 2018-6-18 16:55
There is no exact explanation. That's what i need to know. What causes YAW ERROR and HOW TO PREVENT IT.

Post #15 and #24

https://forum.dji.com/thread-151297-1-1.html is #15

Please look at #24 too

pmshop Posted at 2018-6-18 13:06
@Mirek6

Very good analysis but lacking one thing - mass forum posting of this issue started in April.

pmshop,

You write: "Very good analysis but lacking one thing - mass forum posting of this issue started in April.
Unless DJI changed IMU manufacturers or specs of the IMU, the issue would have "always been" since the beginning."

I cannot answer this question. I just based my analysis on what I saw in logs. We would need to do similar analysis for other cases and compare. Perhaps there is similarity. Perhaps this one is unique.

Gunship9 Posted at 2018-6-18 14:41
What do you make of the reports that the Spark does not follow the RC stick movements when in ATTI mode?

It doesn't make sense to me.  I think the newbie pilots are mixed up with their orientation when the Spark is facing them.  Or, they are watching the video, as they fly in ATTI mode, and not compensating for video lag as they bang the sticks around.  The Spark has a lot of lag in the video feed.  Too much for unstabilized (GPS) flying.  Hence the need to keep the drone within VLOS when flown.

Gunship9,

You write: "What do you make of the reports that the Spark does not follow the RC stick movements when in ATTI mode? "

In this case it is absolutely not true. Dan's Spark, when it was in ATTIs mode, did exactly what Dan asked it to do. I can see it in the logs:
1m 16 sec to 1m 19.5 sec - full speed back with slight left - roll/pitch and GPS moving as expected.
1m 19.5 sec to 1m 21.7 - short burst of stick to the left, slower back - roll and pitch of the aircraft moves as expected.
1m 21.8 to 1m 23.2 s - sticks released to neutral position - Spark moves by inertia as expected. GPS changes as expected.

KlooGee Posted at 2018-6-18 14:53
I agree largely with Mirek6's analysis of the flight.  Unfortunately, none of us can know for sure what was the reason for the YAW errors, but I have always assumed the same as Mirek6 in regards to something going wrong in the system and causing different sensor systems to provide conflicting data and causing it to drop into ATTI mode.  I also agree that it is very likely that the issue started happening before the Spark's logs actually started indicating there was a problem.  You can see it in the video start to get a bit "slippery" in its movements and not being steady like expected when in full control.

In regards to the "Weak GPS Signal" message at 1:21.5, that is a direct result of the action taken and logged at 1:17.1 where it exited GPS mode and started ignoring all GPS data as far as navigation goes.  I agree with Mirek6's latter thought on this rather than it having anything to do with satellite geo-spacing or anything directly to do with GPS specifically.

KlooGee,

I should have read your post first before answering Gunship9 :-)
You answered ATTI question and concern first and perfectly! I fully concur that, from analysis of stick movements and Spark's response, it was spot on in ATTI. No problem there. Everything as expected - including inertia.

SparkChog Posted at 2018-6-18 16:55
There is no exact explanation. That's what i need to know. What causes YAW ERROR and HOW TO PREVENT IT.

SparkChong,

Although you want one answer to what causes YAW errors, there is no one answer. pmshop pointed you to some posts and articles which will show you that there may be multiple causes.

But to spare you long reading (although I do encourage you to read these posts and articles) Yaw error means simply disagreement between drone's compass and IMU. Which can be caused by plethora of things. It may be accompanied by some other errors when Spark's complex navigational system is confused.

The best way to prevent it is to read and follow all the good advice, articles and videos posted on this forum and study Spark's manual.
The bad news is - sometimes you simply can't prevent it. As was in this particular case.

Mirek6 Posted at 2018-6-18 18:59
Gunship9,

You write: "What do you make of the reports that the Spark does not follow the RC stick movements when in ATTI mode? "

That's what I figured.  I was skeptically open to somehow the Spark ignores the sticks when it drops into ATTI mode.

Lots of RC airplanes have gone down with the newbie/unskilled pilot claiming it wasn't following his controls.  It always turns out he was giving it the wrong inputs, which it followed.  

Figure this guy was a Spark pilot:

Gunship9 Posted at 2018-6-18 14:31
Since you say this is a design issue, do you know of a drone that is easy to fly in ATTI mode?  One that beginners or first time drone owners can fly without GPS stabilization?  It sounded like the Spark did respond to stick movements but with a video delay to its response (when not flown in VLOS).

I think being able to fly in ATTI mode, or at least keep it near you, is an essential skill for all drone pilots.  Issues as pilots learn to fly better happens with all radio control aircraft (assuming you wrecked your planes and helicopter when learning).

I see no correlation between the fact that I say it is a design issue (indeed it is) and the simplicity to fly it in atti mode.

Yes, the usual toy quads (same weight as spark) are far easier to control than the Spark in atti mode(at least my spark in my experience) as they do not jump to speeds above 70km/h in a few meters which is visible in my flight log.

Yes I am able to fly in atti mode as you may see that I bring in back from 80+ meters away and safely landed but still my skills is not what we are talking about but instead what DJI is doing for an abnormal behavior which is affecting a huge amount of Spark users.

KlooGee Posted at 2018-6-18 14:53
I agree largely with Mirek6's analysis of the flight.  Unfortunately, none of us can know for sure what was the reason for the YAW errors, but I have always assumed the same as Mirek6 in regards to something going wrong in the system and causing different sensor systems to provide conflicting data and causing it to drop into ATTI mode.  I also agree that it is very likely that the issue started happening before the Spark's logs actually started indicating there was a problem.  You can see it in the video start to get a bit "slippery" in its movements and not being steady like expected when in full control.

In regards to the "Weak GPS Signal" message at 1:21.5, that is a direct result of the action taken and logged at 1:17.1 where it exited GPS mode and started ignoring all GPS data as far as navigation goes.  I agree with Mirek6's latter thought on this rather than it having anything to do with satellite geo-spacing or anything directly to do with GPS specifically.

That is very coherent, thank you. The first fly away experience of a Spark I seen it in one of your YouTube videos last year when I was thinking to buy the Spark, I remember your face

On top, it might be that I was underestimating the max speed as I was still full throttle as I do in GPS mode with sensors on and the I underestimated the inertia.

But this is one thing, what is concerning me is why is this happening, on my previous flight I was 96 meters high, with the same issue it would have been for sure a bye bye Sparky.

Mirek6 Posted at 2018-6-18 15:05
Dan,

You are right - your gimbal movements are abnormal. I am not talking about when you are in Sport mode but regular flying. Your gimbal's gyroscope did not work well.

Still not, I wait for DJI response first as I have an open ticket for more than 24 hours now.

Mirek6 Posted at 2018-6-18 19:15
SparkChong,

Although you want one answer to what causes YAW errors, there is no one answer. pmshop pointed you to some posts and articles which will show you that there may be multiple causes.

@Mirek

Thanks. Hope it won't happen to me.
So far, I have about 28 flights (3hr 14min in total) and everything works perfectly.
Highest altitude of 120m and farthest at 800m without using RTH, this is also to practice my flying skills not just relying on auto modes of spark.. .

Excellent write up of the problem many have had since the .900 firmware roll out, most of which were obtusely dismissed as 'pilot error'. Now imagine getting this problem AND your AC/RC disconnecting at the same time!!

I got almost the exact same problem as Dan except i was just moving my Spark directly vertical, no (intentional anyway) horizontal inputs. I got the cascade of errors then the Spark just took off faster than i've ever seen it move before. Fortunately my connection stayed in place and i was able to wrestle it back to the ground. The 'Fly away' part of it has nothing to do with wind, the Spark pitches aggressively and is under full power, Kloo Gee's explanation is the only feasible one i've seen offered so far.

MKPSG12 Posted at 2018-6-19 00:09
Excellent write up of the problem many have had since the .900 firmware roll out, most of which were obtusely dismissed as 'pilot error'. Now imagine getting this problem AND your AC/RC disconnecting at the same time!!

I got almost the exact same problem as Dan except i was just moving my Spark directly vertical, no (intentional anyway) horizontal inputs. I got the cascade of errors then the Spark just took off faster than i've ever seen it move before. Fortunately my connection stayed in place and i was able to wrestle it back to the ground. The 'Fly away' part of it has nothing to do with wind, the Spark pitches aggressively and is under full power, Kloo Gee's explanation is the only feasible one i've seen offered so far.

Although my flight logs are saying different it was for me as well that spark was hardly pitching and also visible in FL reaching 72km/hour...now this is a record. Anyhow we were both able to control it sign that it was responding to our inputs.

Once again, I do not care if it was responding or not and how skilled I should be to fly atti, my issue is WHY is this drone going out of GPS mode and have all this errors?

And yes, thank you all for the contribution but still no answer from DJI?

Hi all! I had a similar experience this weekend, the drone went into ATTI mode but I was able to control it and bring it back. This is the flight log: https://app.airdata.com/main?share=oQDMJF&page_id=GENERALDetails

Some details:
- Latest firmware on drone and RC - DJI GO 4.2.16 with OTG
- As you can see I was basically in the middle of nowhere, so no power lines or stuff that could cause magnetic interference
- There was no "compass error" (or I didn't notice / they were too fast) on my display (the errors you see at 6:19 and 7:25)
- I went full throttle forward in sport mode at about 7:30 and soon I lost connection
- I heard him going up after a little while (10-15 seconds) and I regained connection, the app was beeping and the drone was returning home
- All of a sudden, something happened and I saw ATTI on the screen. The drone was basically drifting with the wind (not very strong but there was some wind), so I tried to bring it down balancing the wind, he went back to classic GPS when it was near me so I landed him as usual.

I recorded everything so I can also upload the full video. I'm not sure but I from the video looks like ATTI mode (and Yaw errors) triggered right after the drone reached its RTH altitude (50mt) and turned to come back to me. Does this make sense?

Mirek6 Posted at 2018-6-18 12:13
Hey DMX_MT,

I am flattered. But I would be as happy if DJI proved me wrong.

I read your posts Mirek and I agree with you.

Thank you for taking time to reply, I wish that now DJI will come back and tell us their part, so that we can know what this IMU Problem is.

unlink Posted at 2018-6-19 01:18
Hi all! I had a similar experience this weekend, the drone went into ATTI mode but I was able to control it and bring it back. This is the flight log: https://app.airdata.com/main?share=oQDMJF&page_id=GENERALDetails

Some details:

Thank you for sharing your experience.

Welldone in Recovering your Drone back.

Keep tuned as we are waiting the Response from DJI Support on these type of cases of ' YAW ERROR ' so they can tell us what is causing this problem.

Dan O Posted at 2018-6-19 00:19
Although my flight logs are saying different it was for me as well that spark was hardly pitching and also visible in FL reaching 72km/hour...now this is a record. Anyhow we were both able to control it sign that it was responding to our inputs.

Once again, I do not care if it was responding or not and how skilled I should be to fly atti, my issue is WHY is this drone going out of GPS mode and have all this errors?

DJI Support, we are waiting for you response on this case please.

DMX_MT Posted at 2018-6-19 01:51
DJI Support, we are waiting for you response on this case please.

CAS-1900122-B3J2T3

So, close to 48 hours and still no official answer either in the open case or here.

@Dji Moderator: could you please let me know at least when I will have your official position and proposal  of resolution for my (and hundred others)  resolution?

P.S. As you appear not to acknowledge the issue I will start a pool and collect case No's with the same issue from multiple users on different sites (this forum, Facebook groups, samd), I am confident you have this data's but I will help you make it public as you keep on ignoring us.

Dan, we're sorry for the troubles. Is there any error message when the issue appears? Could you upload the original flight records and flight logs for analysis? Thanks in advance!

Dan O Posted at 2018-6-18 21:36
That is very coherent, thank you. The first fly away experience of a Spark I seen it in one of your YouTube videos last year when I was thinking to buy the Spark, I remember your face

On top, it might be that I was underestimating the max speed as I was still full throttle as I do in GPS mode with sensors on and the I underestimated the inertia.

Speaking of the "fly away" I had in the video you mention, I need to go back to that and do a follow up analysis video of it now that I've got a bit more knowledge and experience.  In that particular case, I think it was 100% user error on my part taking off right next to a big chunk of iron (old farm implement) and flying closely up a metal windmill.  

Your case appears to be a different scenario than mine.  Unfortunately I think only DJI will be able to for sure identify what the root cause was.  However, if the past serves as any indication, I highly doubt you will get a specific answer from them.  If they do anything, they will just do a firmware update and not provide any explanation.

I think you are far from the first to underestimate the speed difference between governed GPS flight and full-tilt ATTI mode.  I helped another gentleman a few weeks ago that was flying in a narrow canyon that lost GPS and went into ATTI mode.  Unfortunately for him, he was in Tripod mode when it flipped to ATTI mode and he was in fairly close proximity to the canyon wall.  Even with fairly quick reaction, he couldn't respond quick enough to avoid the canyon wall and drop into the creek below.  In his case, he was an experienced FPV pilot.  However, his case was different from yours in that I think the decision to fly in a narrow canyon and repeatedly ignoring multiple low GPS signal warnings was the root cause for his crash.  

Best of luck to you in your pursuit of getting an answer!  Definitely keep us in the loop as you proceed.  

DJI Susan Posted at 2018-6-19 03:31
Dan, we're sorry for the troubles. Is there any error message when the issue appears? Could you upload the original flight records and flight logs for analysis? Thanks in advance!

All the info's and the flight record was posted already. On top I did send it in the case No above. Would be nice if you will starting giving me answers instead of questions I have already answered before.

DJI Wanda told me in this post that the data's are already sent for analyze, should I understand she was giving me false information?

Nevertheless I will upload the log file again. All the error messages and a complete time frame is visible in my initial post.

Here is the log:

http://www.phantomhelp.com/logviewer/3NF3ZGNPYY9TY68FJVW7/

Mirek6 Posted at 2018-6-18 19:15
SparkChong,

Although you want one answer to what causes YAW errors, there is no one answer. pmshop pointed you to some posts and articles which will show you that there may be multiple causes.

Mirek,

Please help me understand the following:



How was I able to accelerate at such a high level in less than 1 second?

On the second picture here I do not understand how I was able to reduce the speed from 43.5 miles an hour to zero again in less than a second when my input was still full throttle at that time. More than this the acceleration afterwards is very slow which is unusual for atti mode.

Dan O Posted at 2018-6-19 05:42
Mirek,

Please help me understand the following:

Dan O,
The PhantomHelp page only shows some of the information.  Below is a screenshot from the CSV file that PhantomHelp exports from the log file.  As you will see, there are 2 different speeds recorded.  I believe one is based on the accelerometers/IMU and the other is from GPS.  You will see that for the moment you mention, the GPS speed is consistent whereas the speed coming from the accelerometers/IMU is not consistent.  In this case, I think the GPS data is likely to be more reliable.

KlooGee Posted at 2018-6-19 05:54
Dan O,
The PhantomHelp page only shows some of the information.  Below is a screenshot from the CSV file that PhantomHelp exports from the log file.  As you will see, there are 2 different speeds recorded.  I believe one is based on the accelerometers/IMU and the other is from GPS.  You will see that for the moment you mention, the GPS speed is consistent whereas the speed coming from the accelerometers/IMU is not consistent.  In this case, I think the GPS data is likely to be more reliable.

Ok, I seen it now, so one of the speeds, the one hardly decelrating is false, might be the gps one as the drone had issues understanding it's own position, no?

Dan O Posted at 2018-6-19 05:57
I only see one speed in the pic you uploaded, both in miles per hour and in meters per second, but only one...

Columns K and L are the IMU speed in mph and m/s respectively.  Columns M and N are the GPS speed in mph and m/s respectively.