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Home point accuracy issues
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thirkelljjt
lvl.1

United States
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Is there a way to improve the accuracy of your DHP?

I was flying my P3A this morning in a new location (with GPS) and noticed in the map view on the Pilot app the home point it picked up is about 300 meters south of my real position and unfortunately in the middle of a river. This has some obvious concerns .. fortunately I landed safely as i didn’t have to use RTH. (I should note here that i usually fly in Atti mode as my normal fly spot cannot pick up a consistent signal required for GPS)

anyway... Back inside when I look at my tablet (Same one i hook into my controller to fly) and use google maps it is very accurate (Im inside with Wi-fi available, my tablet has a sim slot but its empty) if i switch to my DJI pilot app map under the same situations its way off mark and I’m back in the river ??!!!

Thanks



2015-6-4
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sploodge
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If you fly in an area with BAD GPS then its not a case of accuracy of the Phantom.. I suggest you find a good take off position that HAS good GPS coverage. I think you are taking off with no HP and the Phantom is picking one up after ( when you are over water ) You can always manually set a HP after takeoff manually using the Pilot App and make sure its not over water.

If you take the Phantom to a area that has good GPS coverage, does it set the HP correctly when on the ground?

Not had this issue myself so dont know what to suggest


Remember to buy extra propellers and one or two spare batteries to keep you flying
www.Phantom-Guide.co.uk - The Ultimate Phantom 3 Resource

2015-6-4
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thirkelljjt
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United States
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sploodge Posted at 2015-6-5 15:25
If you fly in an area with BAD GPS then its not a case of accuracy of the Phantom.. I suggest you fi ...


Thanks i will try the Manual option, i assume i just tap the location on the map screen and it relocates where i want that Homepoint to be?

Oddly enough i chatted to another friend who lives in Hong Kong and he has a similar issue (His current location is accurate in Google maps but NOT in the DJI pilot map) maybe its something about the pollution here that messes with the pilot app
2015-6-5
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sploodge
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thirkelljjt Posted at 2015-6-5 16:24
Thanks i will try the Manual option, i assume i just tap the location on the map screen and it rel ...

In the latest App ( IOS ) you can tap the home point button on the left and set it to the phantoms location ( or to the transmitter location if the iDevice has GPS built in ).. Not sure the Android App is updated to have this feature yet..

I will test the map thing out when I get time.. Worth noting , on an IOS Apple device the Pilot App uses the Apple Maps and on an Android Device it uses Google maps. There is no DJI maps as such.. I will try and test your issue though..
2015-6-5
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david.p.mann
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Several detailed comments that may help you:

First, the map screen has three views or layers - Standard, Satellite and Hybrid.  When confirming your aircraft and RC positions, I recommend using only "Satellite" or "Hybrid" view as the map images displayed are based on satellite photos instead of the potentially-flawed and/or inaccurate map "drawings" shown in Standard map view.

Second, the P3's current aircraft position (red arrow) is updated continuously any time the P3 battery is powered on (even when the propellers are not running).  However, the aircraft Home Point is only updated AFTER turning on the propellers.

Third, after powering on the P3 and calibrating the compass but BEFORE turning on the propellers, ALWAYS check your current indicated aircraft position (red arrow) and RC position (blue dot) on the map in satellite (or hybrid) view mode.  Assuming you are holding the RC within a few feet of the P3, the aircraft position (red arrow) and RC position (blue dot) should be within a few feet of one another on the map AND you should confirm these indicated positions are, in fact, accurate.

The P3, P2 and Inspire quads all occasionally get a bad GPS fix on initial battery power-up, even after successful compass calibration and "Ready to Fly" are displayed (7+ satellites).  This is more likely to happen on your first flight of the day in a new location.  Even with 7+ satellites, I have seen inaccurate positions shown on the satellite view map.  The worst I have personally seen has only been about 50 feet with both my Inspire and P2 (once or twice in 30+ flights on each).  

BUT - even this "small" error of 50 feet could be a big problem.  Let me explain.  If you take off in GPS mode with a bad GPS fix and an inaccurate current aircraft position and the P3 then gets a good/accurate GPS fix in the air, the flight control software MAY interpret this as the aircraft getting suddenly moved out of position by a wind gust. It MAY then suddenly try to fly back to the original "incorrect" Home Point.  I'm not talking about a Return to Home (RTH) event; I'm talking about the P3 taking off at full speed at current altitude in the direction of the incorrect original aircraft position/home point because it THINKS it just got blown out of position by the wind.  I believe this is, in some cases, what people have reported as a fly-away event. If this situation occurred, your aircraft could suddenly fly full-speed into a nearby tree, building or people!

THE FIX:  To avoid this, hopefully, rare possibility, check your indicated aircraft position (red arrow) on the map (in satellite view mode) before turning on the propellers.  If you observe a bad initial GPS fix (incorrect aircraft position), pick up your P3 and walk around with it in a large circle so it can see more satellites or, at least, recalculate its position several times because its moving. Hopefully, you will then get a good GPS fix. If you are in an area where the aircraft's view of GPS/GLONASS satellites is hindered, you may have to move to another area with a clear view of the sky.  Set the P3 down, check the satellite map, if the current aircraft position is now accurate, you are good to go.

Fourth, after powering on the aircraft propellers, the Home Point position will update.  Now, BEFORE taking off, check the updated Home Point position (green circle with H) on the map in satellite (or hybrid) view mode, as instructed by the nice lady's voice on the DJI Pilot app. It should be the same as the current indicated aircraft position (red arrow) and should accurately reflect the aircraft's actual current position.  If not, something is wrong.  Don't take off until you figure out what is causing the aircraft's current position and/or home point to be incorrectly indicated.

Finally, based on a few other threads in this forum, before taking off you should also check that the aircraft's orientation (direction nose of P3 is facing) is correctly shown on the satellite map. Also, check that the P3's orientation relative to the RC is correctly shown on the compass graphic in the lower left-hand corner of the DJI Pilot app Camera screen.  In some RARE reported cases, this orientation can get 180 degrees out of whack. A couple reports suggest this MAY lead to all flight controls getting reversed, which would result in a nearly impossible to control aircraft.  This is pure speculation.  But it certainly can't hurt to check the accuracy of the indicated aircraft orientation.  If it's not correct, I'd suggest performing another compass calibration.  
2015-6-5
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clkilljoy1
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Flight distance : 15207 ft
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david.p.mann@ea Posted at 2015-6-5 23:01
Several detailed comments that may help you:

First, the map screen has three views or layers - Stan ...

Definitely detailed.  Can not add anything to that.
2015-6-5
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thirkelljjt
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Hong Kong
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david.p.mann@ea Posted at 2015-6-5 23:01
Several detailed comments that may help you:

First, the map screen has three views or layers - Stan ...

Thanks for that information will run with that next time I'm out
2015-6-5
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JtrJr-Droner
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Flight distance : 4341 ft
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david.p.mann@ea Posted at 2015-6-5 23:01
Several detailed comments that may help you:

First, the map screen has three views or layers - Stan ...

David,

Great information in a well written format. Thank you for providing the input!

Jerry
2015-6-6
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edde_m
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Czechia
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david.p.mann@ea Posted at 2015-6-5 23:01
Several detailed comments that may help you:

First, the map screen has three views or layers - Stan ...

Hi David,

I read your info great help thanks, I wonder if you could help I had an issue with setting my home point. I went through all the procedure normally but I kept having a message that my home point was not recorded. However on the map the H symbol was showing me that i had my Home point well set. Do you have any idea what could provoke conflictual info ? I have finally taken off carefully and provoked a RH which worked well. I there a a known bug in the software? In all cases I am quite nervous I do not know what to trust the Map or the RC message .. thanks for your light. M
2015-7-16
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david.p.mann
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edde_m Posted at 2015-7-17 14:08
Hi David,

I read your info great help thanks, I wonder if you could help I had an issue with set ...

edde_m,

I've never had the DJI Pilot app tell the home point was NOT recorded, so I've not dealt with that situation personally.  However, if you are getting conflicting information from the app, the standard recommendation from the DJI contacts on this forum and from other forum regulars is to delete the DJI Pilot app from your mobile device and then reinstall it.  Give that a try and see if that eliminates your reported issue.

On what mobile device and operating system version are you running the DJI Pilot app?
2015-7-17
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CaveDrone
Second Officer
Flight distance : 11549 ft
United States
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david.p.mann@ea Posted at 2015-6-5 23:01
Several detailed comments that may help you:

First, the map screen has three views or layers - Stan ...

Great information!
2015-7-17
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edde_m
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Czechia
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david.p.mann@ea Posted at 2015-7-18 09:20
edde_m,

I've never had the DJI Pilot app tell the home point was NOT recorded, so I've not dealt  ...

I am using ipad air 2 so ios operating system. Shall i go ahead and re-install the software on my ipad ? This problem started when i did a software update actually. Thanks
2015-7-17
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edde_m
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Czechia
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david.p.mann@ea Posted at 2015-7-18 09:20
edde_m,

I've never had the DJI Pilot app tell the home point was NOT recorded, so I've not dealt  ...

Hi , i have installed again the ipad software and it works well now. Thank you for your advice. M
2015-7-18
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Swiss Tony
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Flight distance : 505459 ft
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edde_m Posted at 2015-7-17 14:08
Hi David,

I read your info great help thanks, I wonder if you could help I had an issue with set ...

Hi edde_m, I also get this message whenever I try and manually set the home point, I don't understand it. I've tried setting it to both of the options but get the same message. It updates itself every time and is fine, but I would very much like to know what I/ we're doing wrong here. I checked the instructions and it only tells you how to set the home point. Can anyone offer any advice? I'm going to start a thread on it, I've not worried about it previously but now I think about it I should really figure it out.

The tips from david.p are good. I was testing my new Polarpro filters yesterday and on one of the flights my P3 clearly wasn't stable. It was in GPS mode but was trying to fly as if I had calibrated it on a slope. It was doing so in different directions thoughIt was at about 15 feet when I released the throttle to check its stability which is something I do as standard now before sending it too faraway. It was really tricky to get it back and down, it ended up flipping onto its roof on landing and ruined a set of props but at least it was intact. I recalibrated it and it was fine. Good job that I learnt to fly on the Blade mCPX heli so I have fast fingers, those things are crazy!
I have to fly without the Ultrasonic until DJI figure out what's going on with it, I got "Land Immediately" messages, they took it back and replaced it but the new one did it again and they've just said to turn it off for now. This means that up to about 10 feet, it doesn't hover as perfectly as it normally would. I would recommend to everyone that after take off, they put it into a hover at about 10 feet and see how it behaves.
2015-7-18
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mtnmaddman
Second Officer
United States
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wow mine did that once also to the south "exactly and about 300 meters,  I have no idea what was going on,  earth shift
2015-7-18
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mtnmaddman
Second Officer
United States
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david.p.mann@ea Posted at 2015-6-5 23:01
Several detailed comments that may help you:

First, the map screen has three views or layers - Stan ...

I agree with everything that you have said, I am not sure though if I am reading right that you say to calibrate compass every flight?  On page 49 of the manual the way I read it is, that there may be two meanings to pre flight .  

The pre flight before you fly for the first time, and the pre flight between each session or flight.  I am interpreting the pre flight referred to on pg.49 is the preflight procedure befpre the first flight, it then says recalibrate if you move to a different location.  

I totally agree with the preflight orientation check, I do this every time,  if the app is not calling for a compass calibration I don't think it is necessary to do it.  you may calibrate something in that is spurious at the moment,  almost every fly off starts with I calibrated the compass or Imu or both.

I calibrated my p2 only on occasion the app. called for it once or twice in a year, I calibrated when I moved around , and not always, no trouble what so ever.  You don't go out and unhook your battery wire on your car , to reset the computer every so often, or every time you drive it.
2015-7-18
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david.p.mann
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I only calibrate my compass once before the first flight at a new location.  But you need to make sure its a good calibration with no magnetic interference.  For example, don't try calibrating P3 compass while standing on a concrete driveway or roadway with rebar.
2015-7-18
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david.p.mann
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edde_m Posted at 2015-7-19 06:47
Hi , i have installed again the ipad software and it works well now. Thank you for your advice. M

Good - glad to hear it!
2015-7-18
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edde_m
lvl.1

Czechia
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Swiss Tony Posted at 2015-7-19 09:16
Hi edde_m, I also get this message whenever I try and manually set the home point, I don't underst ...

Hi,  as i wrote re-installing the software did the trick.  Now that you talk about a slope, i must mention that my problem occured also may be because i turned on P3 on top of a hill then moved down to find a flat spot. When i found a flat spot i did my procedure and wanted to set a Hp. This is when the map was showing the H and the sofware on my ipdad was telling me no home point was set. Eventhough i restarted  my Ipad and the RC the problem wad still there. The p3 must have freaked out trying to find out what is going on. So i suggest to turn on p3 on the spot of taking off and not before. ..
2015-7-19
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Swiss Tony
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Flight distance : 505459 ft
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edde_m Posted at 2015-7-20 03:34
Hi,  as i wrote re-installing the software did the trick.  Now that you talk about a slope, i must ...

I always do edde, this flight just got messed with by Gremlins. It was pitching all over the place like rodeo, to an unknowing bystander it would've looked like I was a crappy pilot but anyone who knows how hard it is to fly and land an out of control copter would've high fived me. After they'd come out from behind whatever they jumped behind for cover!
2015-7-19
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