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A funny thing happened on my RTH today
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547 43 2018-7-4
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DennisM
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I was out for a fly today when I decided to do a RTH with 34% battery left.  It came home quite nicely until the last 20/25 feet off of the ground when it suddenly lurched to the side and started drifting away from the home point.  I gained control with the sticks and landed it about 15/20 away.  I looked at the controller and saw a low battery warning.  Could this have interruped the landing?  Could this happen a couple of hundrend feet out on a RTH and battery warning kick in?  I am really curious.

I have have the 4 pro + v 2.0.  It's just over a week old.

Thanks
2018-7-4
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Labroides
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The most likely explanation is obstacle avoidance.
Were there obstacles close by that could have set it off or were you in an open area?
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Mark The Droner
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A low battery wouldn't cause it to lurch.  Sounds like you lost the satellite connection.  Check your log.  
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RedHotPoker
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Mark The Droner Posted at 2018-7-4 13:30
A low battery wouldn't cause it to lurch.  Sounds like you lost the satellite connection.  Check your log.

May as well share the link, for checking a drone flight LOG.

http://www.phantomhelp.com/LogViewer/Upload/


RedHotPoker


2018-7-4
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Nigel_
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If it was low light conditions, maybe around sunset then most likely just a GPS error, maybe a switch to a different satellite.  You only notice these things when it is close by and fairly low down.  One reason for keeping it above head height at all times, especially when hand catching.  We should be able to see this in the logs...
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ALABAMA
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"  I gained control with the sticks   "

Did you cancel RTH before you did this?, or was it auto landing?
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Labroides
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Nigel_ Posted at 2018-7-4 14:03
If it was low light conditions, maybe around sunset then most likely just a GPS error, maybe a switch to a different satellite.  You only notice these things when it is close by and fairly low down.  One reason for keeping it above head height at all times, especially when hand catching.  We should be able to see this in the logs...

If it was low light conditions, maybe around sunset then most likely just a GPS error, maybe a switch to a different satellite.

Low light affecting GPS ???
That would be a first.
Low light and sunset have no effect on GPS.
Switching to a different satellite  ??
That's not how GPS works.
Your GPS uses lots of satellites at the same time.
It can't work with just one (or 2 or 3)
Switching to a different satellite isn't an explanation for anything.

Flight data would show what was happening with GPS but it's extremely unlikely it affected the flight as described.

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DennisM
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RedHotPoker Posted at 2018-7-4 13:35
May as well share the link, for checking a drone flight LOG.

http://www.phantomhelp.com/LogViewer/Upload/

log doesn't appear to show anything.  How do I get if off of the controller?  There's nothing on the sd card.
2018-7-4
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Labroides
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DennisM Posted at 2018-7-4 14:13
log doesn't appear to show anything.  How do I get if off of the controller?  There's nothing on the sd card.

Go to http://www.phantomhelp.com/LogViewer/Upload/
Follow the instructions there to upload your flight record from your phone or tablet.
Come back and post a link to the report it gives you.
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RedHotPoker
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DennisM Posted at 2018-7-4 14:13
log doesn't appear to show anything.  How do I get if off of the controller?  There's nothing on the sd card.

As suggested from Labroides, follow the instructions, and then please post a link to the LOG. Thanks.



RedHotPoker
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DennisM
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ALABAMA Posted at 2018-7-4 14:10
"  I gained control with the sticks   "

Did you cancel RTH before you did this?, or was it auto landing?

No........
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RedHotPoker
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DennisM Posted at 2018-7-4 14:13
log doesn't appear to show anything.  How do I get if off of the controller?  There's nothing on the sd card.

Post the LOG link.



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Nigel_
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Labroides Posted at 2018-7-4 14:12
Low light affecting GPS ??? That would be a first.


We get GPS variations all the time, but normally don't notice them because the Vision Positioning corrects them.  In low light conditions the Vision Positioning turns off and then we see unexpected movements due to GPS errors, most likely while landing since that is the only time the aircraft is close enough to see them.

Actually sunset is the worst time for accurate GPS, the atmospheric conditions caused by sunset affect the timing of the radio signals and it is actually less accurate.

We need the log, or we are just guessing!
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Labroides
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Nigel_ Posted at 2018-7-5 00:17
We get GPS variations all the time, but normally don't notice them because the Vision Positioning corrects them.  In low light conditions the Vision Positioning turns off and then we see unexpected movements due to GPS errors, most likely while landing since that is the only time the aircraft is close enough to see them.

Actually sunset is the worst time for accurate GPS, the atmospheric conditions caused by sunset affect the timing of the radio signals and it is actually less accurate.

Sorry Nigel but that's a load of bunk and you're fantasising.
GPS is an all-weather system and sunset, midnight in a snowstorm or an eclipse during the summer solstice has zero effect.
You don't get GPS errors at all.
And even if it had an effect, your Phantom has a minimum of 6 sats to work with and any minor glitch doesn't bounce the Phantom around even with the VPS system off.
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Nigel_
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Labroides Posted at 2018-7-5 00:52
Sorry Nigel but that's a load of bunk and you're fantasising.
GPS is an all-weather system and sunset, midnight in a snowstorm or an eclipse during the summer solstice has zero effect.
You don't get GPS errors at all.

"You don't get GPS errors at all."

Are you saying that GPS is accurate to the mm at all times?

There are a lot of things that can affect accuracy, but normally we don't see them because of the VPS.
The OP said "it suddenly lurched to the side", that does happen occasionally when there is no VPS.  We don't know if the movement was a 10cm lurch, or a 10m lurch but both are quite possible with GPS and no VPS, if it was 100m then GPS is unlikely to have caused it.
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Labroides
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Nigel_ Posted at 2018-7-5 02:38
"You don't get GPS errors at all."

Are you saying that GPS is accurate to the mm at all times?

A GPS error is a specific error condition that's not what you are talking about at all.

Are you saying that GPS is accurate to the mm at all times?
Of course not because I understand how GPS works.
Each GPS fix is going to be slightly out but it doesnt kick the Phantom left and right.
The Phantom uses a smoothing algorithm to prevent that.
It may do a slow slight drift a little this way and a little that way but it never gets a noticeable kick this way or that - never.

There are a lot of things that can affect accuracy, but normally we don't see them because of the VPS.
No ... VPS only works within 10 metres of the ground.
I fly with it disabled anyway and I never see what you are telling me I should.
My Phantom hovers closely just as my earlier Phantoms without VPS did.

AS the OP described his incident, GPS was not to blame.
GPS just doesn't work that way.

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DennisM
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Sorry but I am not successful in downloading the log off of the controller from the 4p+.  I even googled how to do it and followed their screenshots with no luck.  I will give up for now.  If it happens again I will come back to this thread with another effort.  I did read the logs and they looked quite normal but did show the low battery warning as mention in my original post.

I appreciate everyone's help.................I am a photographer first and a drone enthusiast second.

dennis
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Nigel_
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Labroides Posted at 2018-7-5 02:53
A GPS error is a specific error condition that's not what you are talking about at all.

Are you saying that GPS is accurate to the mm at all times?

"No ... VPS only works within 10 metres of the ground."
Yes, that is one reason for thinking that it may have been around sunset at the time, the OP did say "It came home quite nicely until the last 20/25 feet off of the ground when it suddenly lurched to the side" - it lurched about the time the "VPS" became active.   Of course if you never use VPS then you aren't ever going to see VPS related issues!

We need the log before continuing this conversation!
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Mark The Droner
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DennisM Posted at 2018-7-5 03:48
Sorry but I am not successful in downloading the log off of the controller from the 4p+.  I even googled how to do it and followed their screenshots with no luck.  I will give up for now.  If it happens again I will come back to this thread with another effort.  I did read the logs and they looked quite normal but did show the low battery warning as mention in my original post.

I appreciate everyone's help.................I am a photographer first and a drone enthusiast second.

You don't need to google anything.  Everything you need has already been conveniently provided for you in the link.  Simply scroll down to the bottom of the page and you'll see full detailed instructions.  

http://www.phantomhelp.com/LogViewer/Upload/
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RedHotPoker
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Mark The Droner Posted at 2018-7-5 04:07
You don't need to google anything.  Everything you need has already been conveniently provided for you in the link.  Simply scroll down to the bottom of the page and you'll see full detailed instructions.  

http://www.phantomhelp.com/LogViewer/Upload/

I don’t think he wants us to see the flight LOG.

Oh well. Hopefully he is having  fun...  ;-)


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RedHotPoker
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DennisM Posted at 2018-7-5 03:48
Sorry but I am not successful in downloading the log off of the controller from the 4p+.  I even googled how to do it and followed their screenshots with no luck.  I will give up for now.  If it happens again I will come back to this thread with another effort.  I did read the logs and they looked quite normal but did show the low battery warning as mention in my original post.

I appreciate everyone's help.................I am a photographer first and a drone enthusiast second.

We offered to help, you didn’t want to share the flight LOG.

That’s where it ends.

Good luck. Hope you have great success in the future.



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Aardvark
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A nice little article here on GPS

https://www.gps.gov/systems/gps/performance/accuracy/
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Labroides
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Nigel_ Posted at 2018-7-5 03:53
"No ... VPS only works within 10 metres of the ground."
Yes, that is one reason for thinking that it may have been around sunset at the time, the OP did say "It came home quite nicely until the last 20/25 feet off of the ground when it suddenly lurched to the side" - it lurched about the time the "VPS" became active.   Of course if you never use VPS then you aren't ever going to see VPS related issues!

I'll try again ....
We get GPS variations all the time, but normally don't notice them because the Vision Positioning corrects them.
Each GPS fix can be different because of the variable nature of GPS accuracy.
Subsequent fixes will commonly vary by 0.5-1 metre.  
Over time position errors will be even larger.
That's nothing new.
But you don't see a Phantom lurching from point to point in response to GPS position error.
It just doesn't happen, VPS or not.

Actually sunset is the worst time for accurate GPS
Presumably you are referring to changes in the ionosphere.
GPS manufacturers uses a built-in model to correct for this type of error.
The resulting error is not significant enough to stand out.
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ALABAMA
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Can someone just tell me how he gained control of the sticks, as he said, without cancelling RTH?
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djordan2
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I wonder if maybe he was landing too close to himself, and when the sensors saw him they move the drone away.
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Mark The Droner
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ALABAMA Posted at 2018-7-5 14:06
Can someone just tell me how he gained control of the sticks, as he said, without cancelling RTH?

Certainly.  You can steer the AC down while it's descending in RTH.  Sounds like that's what he described.  You don't have to cancel RTH to steer it down.  
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DennisM
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Mark The Droner Posted at 2018-7-5 04:07
You don't need to google anything.  Everything you need has already been conveniently provided for you in the link.  Simply scroll down to the bottom of the page and you'll see full detailed instructions.  

http://www.phantomhelp.com/LogViewer/Upload/

That link is where google took me.  It didn't work for me.  I followed it precisely.  The log was not on the sd card nor did it come through usb cord connected between my desktop and the controller and put any files on my computer.  PA..LEASE........it's not that I don't want anyone to see the logs.  The log is there I have simply lost patience at this point.   If it happens again I will come back to this thread.

Thanks again
dennis
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DennisM
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djordan2 Posted at 2018-7-5 14:23
I wonder if maybe he was landing too close to himself, and when the sensors saw him they move the drone away.

This makes sense.......indeed I was only a handful of feet away, maybe three feet, when it lurched.

Thanks
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Labroides
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DennisM Posted at 2018-7-5 14:57
That link is where google took me.  It didn't work for me.  I followed it precisely.  The log was not on the sd card nor did it come through usb cord connected between my desktop and the controller and put any files on my computer.  PA..LEASE........it's not that I don't want anyone to see the logs.  The log is there I have simply lost patience at this point.   If it happens again I will come back to this thread.

Thanks again

Here's the link:  http://www.phantomhelp.com/logviewer/upload/
It will give you the precise instructions to follow.
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Labroides
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Labroides Posted at 2018-7-5 15:20
Here's the link:  http://www.phantomhelp.com/logviewer/upload/
It will give you the precise instructions to follow.

So post #2 probably was the correct answer after all.
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RedHotPoker
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Like pulling elephant to teeth, without an anesthetic...

The trunk will beat you down... haha


RedHotPoker
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RedHotPoker
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A funny thing happened on the DJI forum today... hahaha


You can read about it, above. Chuckles



RedHotPoker
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Before you chastise him too much, be aware that currently many folks can't get the flight data off the P4 Vr 2.0 or the Plus version, which IMO would be even harder.

The "Assistant 2 for Phantom" which is the New version of Assistant only for the Vr 2.0 on my P4 Vr 2.0 will connect, but it will not let me go to the flight logs.  That was as of 1 week ago.  

I realize there should be a version of the log on the device, as it would be on my iPad for my Vr. 2.0, but on the Plus, you only have the built in display.   One way to get the log would be Assistant 2 for Phantom, which again currently doesn't work for my Mac or PC (connects but will not allow viewing of flight logs when drone is attached via USB).  He might be able to pull them via wifi as the screen on the Plus does have a wifi connectivity.  

With the release of the firmware for the Vr 2.0, I again tried to update via Assistant 2 for Phantom and it was a no go, but the upgrade was possible via djigo4.  

The Vr 2.0 is buggy, but not sure which firmware OP is running on.

Paul C
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Labroides
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paul2660 Posted at 2018-7-5 15:54
Before you chastise him too much, be aware that currently many folks can't get the flight data off the P4 Vr 2.0 or the Plus version, which IMO would be even harder.

The "Assistant 2 for Phantom" which is the New version of Assistant only for the Vr 2.0 on my P4 Vr 2.0 will connect, but it will not let me go to the flight logs.  That was as of 1 week ago.  

Before you chastise him too much, be aware that currently many folks can't get the flight data off the P4 Vr 2.0 or the Plus version, which IMO would be even harder.

But that's irrelevant to using the flight data recorded by the app as was suggested several times to the OP.
Until your post, no-one had mentioned Assistant.

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ALABAMA
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" It came home quite nicely until the last 20/25 feet off of the ground when it suddenly lurched to the side and started drifting away"

Not to beat a dead horse, but something doesn't add up.
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DennisM
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ALABAMA Posted at 2018-7-5 16:09
" It came home quite nicely until the last 20/25 feet off of the ground when it suddenly lurched to the side and started drifting away"

Not to beat a dead horse, but something doesn't add up.

Maybe it was closer to my height...... 6' 1" off the ground.  Then it might add up.

I stand by my being able to see the flight log and not being able to down load it........  It's probably me.

Also, I though all of the sensors were turned off when the bird began the RTH descent.

Thanks all for their input.

dennis
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ALABAMA
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I know what it's like ,lol.  Things like small details can't be remembered when something like that happens.   At least no damage and all ends well.    Have fun flying, and forget about the flukes.
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RedHotPoker
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ALABAMA Posted at 2018-7-5 16:56
I know what it's like ,lol.  Things like small details can't be remembered when something like that happens.   At least no damage and all ends well.    Have fun flying, and forget about the flukes.

Ooh, bad choice of words...
Trematoda is a class within the phylum Platyhelminthes. It includes two groups of parasitic flatworms, known as flukes.

Deworm that drone... haha


RedHotPoker
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ALABAMA
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RedHotPoker Posted at 2018-7-5 17:05
Ooh, bad choice of words...
Trematoda is a class within the phylum Platyhelminthes. It includes two groups of parasitic flatworms, known as flukes.

RHP, Sometimes I don't think you understand all you know lol.   
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RedHotPoker
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ALABAMA Posted at 2018-7-5 17:39
RHP, Sometimes I don't think you understand all you know lol.

Smarter than the average bear?

That’s Grizzly to you. Not Teddy!! Hahaha



RedHotPoker
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