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what if i take off before homepoint recorded?
164 16 2017-4-21 01:38:17
fansce9f006f
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Indonesia
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So many people saying that A/C will keep the last homepoint recorded intact until the new homepoint recorded, thus causing some flyaway.

Example:
Day-1 i flown my A/C at the "A" city with all normal condition, nothing special.
Day-2 i fly at "B" city few miles away from "A" city in a rush, so i can't wait for the "home point recorded" status, that makes me to take off in ATTI mode.

Suppose RTH triggered in this last flight (regardless failsafe or smart), will the A/C going home to the homepoint of Day-1 ???

If any flightlog data/video/review about this, please be kind to show me.... [emoji4] [emoji4] [emoji4]
2017-4-21 01:38:17
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Nigel_
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That might depend on which aircraft, which firmware and how you fly it.

For example, in this log from a P4, the home point gets set automatically after take off, at 78ft altitude, however the aircraft thinks that it is still over the take off point, although I'm not sure how it knows that: http://forum.dji.com/forum.php?m ... &fromuid=316867

Best to check that it is set as part of your pre-launch checks.
2017-4-21 02:06:11
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Labroides
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Australia
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If you launch before the GPS has had time to acquire enough sats for a fix, or from a location where the sky is blocked,  your Phantom will be in atti mode until it gets enough sats for a fix.

Example ... you launch from under tree cover without GPS, fly up and through a gap.
Once up there, your Phantom gets a fix and records the point where this happens as home.

2017-4-21 03:26:57
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Nigel_
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Labroides Posted at 2017-4-21 03:26
If you launch before the GPS has had time to acquire enough sats for a fix, or from a location where the sky is blocked,  your Phantom will be in atti mode until it gets enough sats for a fix.

Example ... you launch from under tree cover without GPS, fly up and through a gap.

That's not the case in the example I linked to, that launches in P-GPS mode but sets the home point later.
I guess it requires a certain GPS quality level before it records the home point.
2017-4-21 03:54:26
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Quamera
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The Phantom will forget the Day-1 homepoint as soon as it is turned off so it won't try to return there on Day-2.
2017-4-21 04:06:11
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Labroides
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Nigel_ Posted at 2017-4-21 03:54
That's not the case in the example I linked to, that launches in P-GPS mode but sets the home point later.
I guess it requires a certain GPS quality level before it records the home point.

The Phantom cannot be in P-GPS mode until it has acquired enough GPS satellites.
Until then, it's in atti mode regardless of the switch position.
Once it has enough sats, it has position holding and records home.
2017-4-21 04:06:17
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fansce9f006f
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Nigel_ Posted at 2017-4-21 02:06
That might depend on which aircraft, which firmware and how you fly it.

For example, in this log from a P4, the home point gets set automatically after take off, at 78ft altitude, however the aircraft thinks that it is still over the take off point, although I'm not sure how it knows that: http://forum.dji.com/forum.php?mod=redirect&goto=findpost&ptid=92471&pid=767673&fromuid=316867

Thanks for your reply Nigel_,

as far as i know form the internal flight log of my Phantom3Adv, there is blank value on the latitude and longitude column until it gain a GPS lock for the first time which means it records the home point.
but why i am asking this while i already has these data is because many people still believe that UAV always keep the last homepoint until it get the new one. that's why i wanna know wether my knowledge is applied only on Phantom3Adv or what.... Thanks again....
2017-4-21 05:20:13
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fansce9f006f
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Labroides Posted at 2017-4-21 03:26
If you launch before the GPS has had time to acquire enough sats for a fix, or from a location where the sky is blocked,  your Phantom will be in atti mode until it gets enough sats for a fix.

Example ... you launch from under tree cover without GPS, fly up and through a gap.

Yes, you're right... and i've done it several times in some situation...
But what i'm asking is..... before the UAV get the HP at the current flight, will it keep the HP coordinates of the previous flight intact ?

Thanks,..
2017-4-21 05:25:32
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fansce9f006f
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Quamera Posted at 2017-4-21 04:06
The Phantom will forget the Day-1 homepoint as soon as it is turned off so it won't try to return there on Day-2.

Thank you very much....
That's exactly what i have in my mind.
2017-4-21 05:26:14
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KM5RG-Robert
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Test it and let us know.
2017-4-21 05:48:58
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Nigel_
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fansce9f006f Posted at 2017-4-21 05:20
Thanks for your reply Nigel_,

as far as i know form the internal flight log of my Phantom3Adv, there is blank value on the latitude and longitude column until it gain a GPS lock for the first time which means it records the home point.

I think there may be some confusion because the map in the Go App will come up at the last location until a new GPS location is acquired.  I've see the map be in the wrong country.  However I don't recall ever seen a log with the home point in completely the wrong place, and if it was then it would instantly do a low battery return to home and the problem would be noticed.

Every time there is a problem with the home point it is because someone has set it from their mobile device and they can sometimes be wildly inaccurate, especially if they don't have a GPS receiver and are using the mobile signal to guess their location.

I'm not convinced that the home point is set on the very first GPS fix though, it may wait for a good quality fix before setting the home point.
2017-4-21 05:54:23
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fans987d278a
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Canada
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Nigel_ Posted at 2017-4-21 05:54
I think there may be some confusion because the map in the Go App will come up at the last location until a new GPS location is acquired.  I've see the map be in the wrong country.  However I don't recall ever seen a log with the home point in completely the wrong place, and if it was then it would instantly do a low battery return to home and the problem would be noticed.

Every time there is a problem with the home point it is because someone has set it from their mobile device and they can sometimes be wildly inaccurate, especially if they don't have a GPS receiver and are using the mobile signal to guess their location.

Why one would not wait for the command- "Home point recorded", if somehow home point isn't recorded, say until you get 20-30 mters away, maybe because bird doesn't get satililte fix,  your home point would then be, 20-30 meters away from you!
But, don't worry about the day before's flight, once you turn off your bird, the last home point is history, so no worries about it going back to a previous  flights home point
2017-4-21 06:30:36
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Nigel_
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fans987d278a Posted at 2017-4-21 06:30
Why one would not wait for the command- "Home point recorded", if somehow home point isn't recorded, say until you get 20-30 mters away, maybe because bird doesn't get satililte fix,  your home point would then be, 20-30 meters away from you!
But, don't worry about the day before's flight, once you turn off your bird, the last home point is history, so no worries about it going back to a previous  flights home point

I am not sure that turning off resets the home point?

I think it may be removing the battery that resets it...
2017-4-21 07:06:05
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Eric13
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Germany
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Nigel_ Posted at 2017-4-21 05:54
I think there may be some confusion because the map in the Go App will come up at the last location until a new GPS location is acquired.  I've see the map be in the wrong country.  However I don't recall ever seen a log with the home point in completely the wrong place, and if it was then it would instantly do a low battery return to home and the problem would be noticed.

Every time there is a problem with the home point it is because someone has set it from their mobile device and they can sometimes be wildly inaccurate, especially if they don't have a GPS receiver and are using the mobile signal to guess their location.

"Every time there is a problem with the home point it is because someone  has set it from their mobile device and they can sometimes be wildly  inaccurate, especially if they don't have a GPS receiver and are using  the mobile signal to guess their location."

I don't think something like a 'wild' homepoint is possible.
If there is no GPS signal available on the device, home point cannot be set to RC. Same thing when AC has no GPS.
I have tried this indoor (with my device having a SIM card and good mobile signal):


HP-1.jpg
HP-2.jpg
2017-4-21 10:45:48
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Eric13
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Quamera Posted at 2017-4-21 04:06
The Phantom will forget the Day-1 homepoint as soon as it is turned off so it won't try to return there on Day-2.

That might make the problem even bigger.
If there is no GPS, latitude/longitude are set to "0" values. I've checked that in the csv file.
The map below shows where those coordinates are.

I have been digging a lot into HP/RTH/GPS topics and find it fascinating.
On my next flight I'll start from a barn or something with no GPS and then fly into the open.
Then I'll trigger RTH. Will let you know if the bird is on its way to Africa :-)

zero home.jpg
2017-4-21 11:46:04
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DJI-Jamie
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Canada
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Nigel_ Posted at 2017-4-21 05:54
I think there may be some confusion because the map in the Go App will come up at the last location until a new GPS location is acquired.  I've see the map be in the wrong country.  However I don't recall ever seen a log with the home point in completely the wrong place, and if it was then it would instantly do a low battery return to home and the problem would be noticed.

Every time there is a problem with the home point it is because someone has set it from their mobile device and they can sometimes be wildly inaccurate, especially if they don't have a GPS receiver and are using the mobile signal to guess their location.

You pretty much hit the nail on the head. The GPS count needs to be stable for at least a few seconds or so before it's properly recorded.
2017-4-21 12:46:31
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Labroides
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Nigel_ Posted at 2017-4-21 05:54
I think there may be some confusion because the map in the Go App will come up at the last location until a new GPS location is acquired.  I've see the map be in the wrong country.  However I don't recall ever seen a log with the home point in completely the wrong place, and if it was then it would instantly do a low battery return to home and the problem would be noticed.

Every time there is a problem with the home point it is because someone has set it from their mobile device and they can sometimes be wildly inaccurate, especially if they don't have a GPS receiver and are using the mobile signal to guess their location.

"I'm not convinced that the home point is set on the very first GPS fix though, it may wait for a good quality fix before setting the home point."

A regular hand-held GPS can give a dodgy 2D fix with 3 sats and a reasonably good 3D fix with 4 sats.
The Phantom has a higher standard and requires either 6 GPS or 6 Glonass sats before it registers a fix.
When the Phantom has a fix, it's a good fix.
2017-4-21 16:44:37
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