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Strange behavior with satellites and DJI Go mode
1116 11 2016-3-19
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mikael
First Officer
Flight distance : 24199 ft
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Sweden
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I was supposed to film in the city center yesterday and film the exterior of a building for a TV show.

I have a Inspire 1 Pro Black edition. Yesterday I used a X3 camera on my I1 Pro. When I started DJI Go (updated) on my Ipad it recognized my I1 Pro as a regular Inspire 1 (not pro). I I restarted the software, my remote and my Inspire and tried again. Same thing. I ended up using the Inspire 1 mode (not pro) in DjI Go.

It was kind of windy. I checked the satellite reception and had between 8-12 satellites and DJI Go said GPS Mode. After liftoff it switched to Atti mode. Since it was kind of windy it started to drift (kind of scary). I landed it to restart the flight again after checking my satellite reception. Again it states GPS mode with between 8-12 satellites. After another Lift off it swichted to Atti mode again. New drifting in the wind. I had to land it again. To risky. After that I aborted everything to make a new try today.

Anyone know why this happened? How many satellites does it need to function in GPS mode? Shouldnt at least 8 be enough? I never saw it go below 8.

Why didnt DJI Go recognize my unit as a Pro unit? Does it automatically use the Non Pro mode because I used an X3 camera on it?

What is the difference between the Pro mode and the Non Pro mode in DJI Go? Anything important?

Please help.

Mikael


2016-3-19
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kvamens
lvl.4

Norway
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.

Don't think satelitte work in Atti mode, that's why it drifting

And i think since you use x3 camera it think you're on regular Inspire
2016-3-19
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Donnie
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That is the whole function of ATTI mode, GPS is disabled.  It is a good idea to practice in ATTI mode because if you do loose GPS this is the mode it goes to.   Also if your aircraft is acting strange in the air from erroneous GPS  signals you can switch to ATTI mode.  I would not train In the beginning in ATTI mode though, get some stick time in and then as soon as you can control the aircraft 100% with the GPS then fly in ATTI mode for at least one flight during a flying session.

Hope this Helps-  Donnie
2016-3-19
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mikael
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Thank you Donnie and Kvamen. I know what ATTI mode is. That isn't the problem. It switched from GPS mode to Atti mode by itself.

My question is: Shouldn't 8 satellites be enough for the inspire to stay in GPS mode? Theoretically 3 satellites should be enough for cross referencing geo points. More is of course preferred. But how many does the bird need to enter and stay in GPS mode?

I didn't have it in ATTI mode. I switched to that mode automatically.

'So how many sats are needed?

And also, Inspire 1 Not Pro mode. Is that due to using the X3? Even though I have an Inspire 1 Pro Black edition bird.

For more info, see my first post at the top please.

Thank You
Mikael

2016-3-19
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jay_herron.yaho
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mikael@ohlen.nu Posted at 2016-3-20 01:56
Thank you Donnie and Kvamen. I know what ATTI mode is. That isn't the problem. It switched from GPS  ...

Any chance you were Downtown? I found when flying downtown L.A., Gps sometimes works, sometimes it doesn't. I shot some Night EXT downtown 2 nights. 1st night it was no problem, 2nd night gps would go on/off into ATTI mode just like you experienced. I believe they have GPS jammers around downtown areas for security issues... Yep, good idea to practice in ATTI mode, its not too bad, just gotta pay a lot more attention...!
2016-3-19
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Mad_Angler1
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United Kingdom
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the lower the number of satellites the less positional data you have, sat count is just a small part of GPS, it's all about the GPS satellite positions and their locations from each other, these are not in geostationary orbit so the number of satellites available to you at the same location is constantly changing.  
2016-3-19
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mikael
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Thanks, I was downtown with semi high buildings around. That may be the reason for not getting perfect reception from a lot of sats. But how many sats does the bird need before switching to ATTI mode?
2016-3-19
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Tharg (from the
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Flight distance : 120784 ft
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This is the problem with people bleating to have the number of satellites received in the display. It is meaningless. Much more important is the HDOP/VDOP quality than any pointless number.
2016-3-20
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Donnie
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    If you are looking for a number I believe it is 6 satellites is the minimum for    GPS lock.  But like Tharg says  it is the quality  of the signal that is very important in the equation.   I am sorry I mis-understood your question.  I have lost GPS and entered ATTI mode when the GO-APP said I had 12 satellites locked, so you need to be ready for it.  

In windy conditions or when there are tall buildings in the area is when i notice I loose GPS function.  Keep in mind it is not only the number of Satellites locked but also if the Aircraft Processor can handle all the data, especially in strong winds.  I hope this helps answer at least part of your question.

Cheers - donnie
2016-3-20
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daver/m
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Donnie Posted at 2016-3-20 06:30
If you are looking for a number I believe it is 6 satellites is the minimum for    GPS lock.  Bu ...

My old phantoms would lock at 7 and after take off and a little altitude would usually show 10 to 17,
My year old inspire won't lock a decent gps signal until 9+  at 7 or 8 the signal strength always flickers back
and fourth from GPS to atti.
Sometimes I'll just take off anyway then when I have a better GPS/Glonas lock I reset the home point to the RC or another appropriate LZ close by. I've also had full bars showing several times with less than the number 7 or 8 showing and the bird stays in atti... at 9 or 10 it's solid and remains stable....Hmmmm. If your flying nearer buildings, city etc,
Then anything could happen signal wise.
2016-3-20
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mikael
First Officer
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thanks for helping with the issue and thanks for clarifying.

Mikael
2016-3-26
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RBirtles
lvl.3

Australia
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Buildings are great at blocking GPS signal.  Just remember that GPS satellites are not always high in the sky and could also be low on the horizon and thus if buildings are around you may find having a few blocked. I am always on alert if I am getting anything less than 13 satellites. Cheers
2016-3-27
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