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How do you tell the Phantom its altitude is 0.0 feet?
2583 25 2015-1-22
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TSP181
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Flight distance : 18258 ft
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Question - what is the procedure for resetting or base lining the altitude to 0.0 feet prior to launch?  Before my last flight my altitude on the iPhone app showed the Phantom V+ 3.0's altitude at 32 feet.   It toggled s2 to reset home point but it didn't change.  I had to keep in mind that I needed to subtract the 32 feet for the entire flight.  

BTW - Yes, I posted a very similar question earlier but it is now gone and I  get a message that says my post is being audited or was deleted by the admin -- WTF?

Thanks,

-TSP181


2015-1-22
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gnixon2015
First Officer

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ok, here goes, not sure if this post will make it with all the reply/forum issues going on but ill try:

i have read a ton on this question because so far i have been unable to use the s2 toggle method to reset my HL or CL.  however, from what I have read, i have not seen any references to the HL reset doing anything to your default altitude.  here are a few thoughts on it from everything i have read but maybe someone else can post up something definitive:

1.  if you actually cant reset the altitude then there is a huge risk of crash if flying in 'non level' areas (like hills, mountains, etc) because if you ever go down below what would be your launch altitude and after that the craft entered into RTH, then it may slam right into a hillside or tree because it doesnt go up far enough.

2.  the only time altitude is used by the craft is:
      a) when calculating if you've exceeded your currently set max altitude
      b) when climging to the RTH altitude when returning home after losing signal or s1Bottom  (naza) or tx loss (phantom/naza)
other than that, i dont see where it would ever 'use' the altitude reading to perform any movement.  i am assuming that if the wind were to 'blow it down' a few meters, it isnt going to go back up (using altitude) to attempt to hold that like it does when trying to regain position using the GPS.  my supposition here is that in GPS mode it wants to hold position but not necessarily altitude (in that it wont return if blown from it but will maintain it if not blown from it).

tsp, when you say you had to keep subtracting, can you be more specific (meaning what exactly were you calculating it FOR or using that info while flying for)?
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COME ON DJI... FIX THIS CRAP... THIS GUY JUST POSTED IN THIS THREAD ACCORDING TO THE MAIN BOARD BUT HIS REPLY IS NOT IN HERE.... YOU REALLY NEED TO FIX YOUR FORUMS (SINCE YOU OBVIOUSLY BROKE THEM LAST NIGHT AS THEY WORKED FINE BEFORE... AND YES, FINE IS A STRETCH *SIGH*):






2015-1-22
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acenothing
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gnixon2015 Posted at 2015-1-23 03:03
ok, here goes, not sure if this post will make it with all the reply/forum issues going on but ill t ...

"if you actually cant reset the altitude then there is a huge risk of crash if flying in 'non level' areas (like hills, mountains, etc) because if you ever go down below what would be your launch altitude and after that the craft entered into RTH, then it may slam right into a hillside or tree because it doesnt go up far enough."

So how does this work if you are on a hilltop and fly to lower levels downhill.  If the RTH is triggered will it hit the hill?
2015-1-22
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gnixon2015
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COME ON DJI... FIX THIS CRAP... THIS GUY JUST POSTED IN THIS THREAD ACCORDING TO THE MAIN BOARD BUT HIS REPLY IS NOT IN HERE.... YOU REALLY NEED TO FIX YOUR FORUMS (SINCE YOU OBVIOUSLY BROKE THEM LAST NIGHT AS THEY WORKED FINE BEFORE... AND YES, FINE IS A STRETCH *SIGH*):

2015-1-22
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gnixon2015
First Officer

United States
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COME ON DJI... FIX THIS CRAP... THIS GUY JUST POSTED IN THIS THREAD ACCORDING TO THE MAIN BOARD BUT HIS REPLY IS NOT IN HERE.... YOU REALLY NEED TO FIX YOUR FORUMS (SINCE YOU OBVIOUSLY BROKE THEM LAST NIGHT AS THEY WORKED FINE BEFORE... AND YES, FINE IS A STRETCH *SIGH*):

2015-1-22
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gnixon2015
First Officer

United States
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COME ON DJI... FIX THIS CRAP... THIS GUY JUST POSTED IN THIS THREAD ACCORDING TO THE MAIN BOARD BUT HIS REPLY IS NOT IN HERE.... YOU REALLY NEED TO FIX YOUR FORUMS (SINCE YOU OBVIOUSLY BROKE THEM LAST NIGHT AS THEY WORKED FINE BEFORE... AND YES, FINE IS A STRETCH *SIGH*):

2015-1-22
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gnixon2015
First Officer

United States
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COME ON DJI... FIX THIS CRAP... THIS GUY JUST POSTED IN THIS THREAD ACCORDING TO THE MAIN BOARD BUT HIS REPLY IS NOT IN HERE.... YOU REALLY NEED TO FIX YOUR FORUMS (SINCE YOU OBVIOUSLY BROKE THEM LAST NIGHT AS THEY WORKED FINE BEFORE... AND YES, FINE IS A STRETCH *SIGH*):

2015-1-22
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gnixon2015
First Officer

United States
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COME ON DJI... FIX THIS CRAP... THIS GUY JUST POSTED IN THIS THREAD ACCORDING TO THE MAIN BOARD BUT HIS REPLY IS NOT IN HERE.... YOU REALLY NEED TO FIX YOUR FORUMS (SINCE YOU OBVIOUSLY BROKE THEM LAST NIGHT AS THEY WORKED FINE BEFORE... AND YES, FINE IS A STRETCH *SIGH*):

2015-1-22
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gnixon2015
First Officer

United States
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COME ON DJI... FIX THIS CRAP... THIS GUY JUST POSTED IN THIS THREAD ACCORDING TO THE MAIN BOARD BUT HIS REPLY IS NOT IN HERE.... YOU REALLY NEED TO FIX YOUR FORUMS (SINCE YOU OBVIOUSLY BROKE THEM LAST NIGHT AS THEY WORKED FINE BEFORE... AND YES, FINE IS A STRETCH *SIGH*):

2015-1-22
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gnixon2015
First Officer

United States
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COME ON DJI... FIX THIS CRAP... THIS GUY JUST POSTED IN THIS THREAD ACCORDING TO THE MAIN BOARD BUT HIS REPLY IS NOT IN HERE.... YOU REALLY NEED TO FIX YOUR FORUMS (SINCE YOU OBVIOUSLY BROKE THEM LAST NIGHT AS THEY WORKED FINE BEFORE... AND YES, FINE IS A STRETCH *SIGH*):

2015-1-22
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gnixon2015
First Officer

United States
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COME ON DJI... FIX THIS CRAP... THIS GUY JUST POSTED IN THIS THREAD ACCORDING TO THE MAIN BOARD BUT HIS REPLY IS NOT IN HERE.... YOU REALLY NEED TO FIX YOUR FORUMS (SINCE YOU OBVIOUSLY BROKE THEM LAST NIGHT AS THEY WORKED FINE BEFORE... AND YES, FINE IS A STRETCH *SIGH*):

2015-1-22
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TSP181
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gnixon2015 Posted at 2015-1-23 03:03
ok, here goes, not sure if this post will make it with all the reply/forum issues going on but ill t ...

Thanks for replying.  The dji app reported that my phantom was 32 feet of the ground BEFORE it lifted off.  I thought that was weird.  New flight, fresh battery, turned it on and it said you're 32 feet up and it was sitting on the ground not flying.   

My S2 toggle wasn't to reset the homepoint.  It was just an attempt to reset the altimeter- which didn't work.   

I don't know why it was 32 feet high but the offset was present the entire flight.   When it was head high it reported about 40 feet high.   

I wi see if it works next flight but there should be a way to tell the phantom it is sitting at zero feet altitude.

TSP181
2015-1-22
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cmgreenejr.emai
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I agree...there is a problem with the altimeter, and it does matter. After every step in a proper pre-flight routine, before takeoff, my altimeter reading is typically non-sensical, sometimes 300 ft., sometimes -325 ft., and changing all the time. I have read posts wherein at that point, before takeoff, you need to power-cycle Phantom, and then reconnect iPhone. In my experience, this doesn't produce a meaningful result. What I end up doing is burning 5 minutes or so of battery, hovering visually about 50 ft. away both horizontally and vertically from me, and then bringing Phantom back to me, landing, power-cycling, then taking off again, and then the altimeter becomes more trustworthy. For sure, the altimeter DOES matter, both in terms of the 400 ft. ceiling, and the RTH altitude.
2015-1-22
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perdidoflyer
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I agree...there IS an issue with the altimeter, and it DOES matter, both in terms of the 400 ft. ceiling, and RTH.
2015-1-22
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TSP181
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cmgreenejr.emai Posted at 2015-1-23 05:31
I agree...there is a problem with the altimeter, and it does matter. After every step in a proper pr ...

I absolutely agree, it does matter.   I was totally afraid to run a ground station mission which was my original plan.  

Is it possible the problem is caused by transporting the phantom in a Go Professional Case.  It is pretty air tight.  

I was really hoping for a way to just tell the system it was at 0.0.  I'm amazed that whatever altitude it is at at power on isn't established as 0.0 feet.
2015-1-22
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bjr981s
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TSP181 Posted at 2015-1-23 11:01
I absolutely agree, it does matter.   I was totally afraid to run a ground station mission which w ...

It can't set the altitude at power on as it has not locked enough satellites to determine its vertical position.

It will only lock its vertical position after locking 6 sats and then a motor start.

i.e. Set home location in all 3 axis.


2015-1-23
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johnwarr.email
Captain
Flight distance : 6467 ft
United Kingdom
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The Phantom uses a barometric sensor to determine its altitude, GPS has nothing to do with it.
Every time the Phantom is powered up it should automatically calibrate its altitude to zero, within a few feet either way.
If you get a wildly inaccurate reading then power off and on again, if that does not work then you need to check the sensor on the leg and try an IMU calibration.   
2015-1-23
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TSP181
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johnwarr.email Posted at 2015-1-23 19:35
The Phantom uses a barometric sensor to determine its altitude, GPS has nothing to do with it.
Every ...

Is the barometric pressure sensor colocated withe the compass?
2015-1-23
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gnixon2015
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jwarr, i was curious on the relationship between IMU and the altitude?  i thought IMU was just for 'level' (attitude).  as for the 'sensor on the leg' is the barometer the one that looks like a small wire (not the white compass box but the other non covered 'wire' that just has tape holding it inside the leg)?
2015-1-23
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kamikaze
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gnixon2015 Posted at 2015-1-23 21:01
jwarr, i was curious on the relationship between IMU and the altitude?  i thought IMU was just for ' ...

The other cable is the antenna
2015-1-23
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johnwarr.email
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The barometric sensor connects to the IMU.
2015-1-23
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TSP181
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I will fly today or tomorrow and see if I'm still off.  If so, I will IMU calibrate and report back.   
2015-1-23
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johnwarr.email
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You don't need to fly, just turn on the phantom and connect your phone as normal, the motors do not need to be running and no GPS lock is needed, so indoors on the table is fine.
Altitude reading should be 0 or a few feet either way, mine is usually somewhere around 2.5 feet.
If the IMU calibration does not fix the issue then you need to check that the tube on the leg is clear and not blocked by any dirt.
Failing all that then the unit will need sending in for repair.
2015-1-23
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TSP181
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I was able to do a props off check.   When I powered it on with it on the gound it said 18 feet.   I poere cyled and it said 8 feet.  Power cycle again and 3.5 feet.   It should be perfect next time I power it on to fly.   Cant explain it but I can probably live with it.   
2015-1-23
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gnixon2015
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unless it goes back up again sometime... very odd... please share future results if you dont mind...
2015-1-23
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firehousekidz
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I have a brand new PV+ Ver 3, I took off with ground Station altitude set at 98 feet. It started heading
For some trees so I took over flight and brought it home only to notice as it was landing the altitude said
78 feet at ground level. I am scared if you locked the  control to land would it slam into the ground thinking it was still along way to land.
2015-1-23
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