compass accuracy Phantom 4 advance/pro

[Dor]

Hello All,
I wasn't able to find in the internet what is the accuracy of Phantom 4 Advance compass (I believe it is similar to the pro)
so if anyone know the answer it will be great, or where i can find those specs

 

[PhantomFandom]

Hi,

I am not sure what kind of accuracy measurement you are looking for. The crucial navigation and orientation instruments (compass, gyroscope, barometer, and compass) are all very accurate across the entire DJI line. I have not heard of or experienced any lack of accuracy, no matter which craft I fly. The instrumentation in my Spark seems every bit as accurate as in my Inspire 2.

 

[Dor]

Thank you for you answer,
But I am looking for specific number of the tolerance of the compass.
For example if I am telling the drone to take a picture from 90° relative to the north, how much it is accurate.
We are talking about tolerance of 1-2 degrees or 10-20

 

[Meta4]

But I am looking for specific number of the tolerance of the compass.
For example if I am telling the drone to take a picture from 90° relative to the north, how much it is accurate.
We are talking about tolerance of 1-2 degrees or 10-20

There's no published data but reading recorded flight data, it's clear that the compass is able to resolve very small angles.
It would not be able to maintain a constant heading otherwise.

How are you wanting to tell the drone to take a picture from 90° relative to the north ?

 

[Dor]

I just have mission from customer to take pictures from specific degrees relative to north, I plan to do it with litchi app.
But I don't find the spec of the compass that I can tell him exactly what is my tolerance

 

[Meta4]

I just have mission from customer to take pictures from specific degrees relative to north, I plan to do it with litchi app.

Here's some sample compass data from a slow turning flight (highlighted in green).
It shows that the compass is measuring to 0.1°

I'm not sure how knowing that makes any difference even if you could find a way to display the heading while you fly.
Because the camera has a very wide angle lens a difference of +/- 5° wouldn't even be noticed.

 

[solentlife]

Basically you cannot.

The compass you have in all these models uses the Magnetic medium and is subject to :

Variation : Local difference of Magnetic North to True North
Deviation : The difference created by the model itself
Local effects : Any influence exterior to the model / compass unit that creates a local anomaly ... iron ore deposits for example ...

This is before we get to errors caused by human intervention such as pipes / cables etc.

The best you can hope for is approximate Magnetic North. It would then need you to correct for Variation of earths True vs Magnetic North.

The purpose of the compass on the model is not as some think to derive North - but to have a reference that direction change of angle can be computed from. The action of saying North is to then reference close enough to North for GPS and Compass together to align to give you Return Home, reference for seeing orientation etc.

If you wish to have single digit accuracy of True North ... then you need either a Gyro or properly setup Fluxgate Compass.

If you do corrections for a location ... as soon as you move from there - the corrections are invalid ... and is why navigational charts carry Variation and Annual rate of change stated in numerous positions on them.
It may not seem important to have such partial or single digit degrees stated on such charts - but take a ship that loses its Gyro Compass ... a single degree can mean many miles off course.

(My principal and original Profession was Professional Ships Senior Navigation Officer).

 

[solentlife]

Here's some sample compass data from a slow turning flight (highlighted in green).
It shows that the compass is measuring to 0.1°

I'm not sure how knowing that makes any difference even if you could find a way to display the heading while you fly.
Because the camera has a very wide angle lens a difference of +/- 5° wouldn't even be noticed.

That's fine but it references to what the Compass see's as its determined Compass to Magnetic North.

If the OP can live with not having exact True North as ZERO and use the angles to select +5 .. +10 etc. then if you can display what the compass output is ... maybe that's good enough ?

 

[solentlife]

I just have mission from customer to take pictures from specific degrees relative to north, I plan to do it with litchi app.
But I don't find the spec of the compass that I can tell him exactly what is my tolerance

Don't forget also that the 'layman' does not realise there are 3 Norths .... Compass North (uncorrected compass result), Magnetic North (Compass North corrected for Deviation and Variation which is presently trucking its way through North Alaska slowly), True North (commonly termed North Pole).

I assume the customer thinks of True North ? Now you need to do some maths and a bit of pre-flight compass work to determine correction to apply.

 

[solentlife]

There is a way to possibly solve it ... overlay the results on a Google Earth map ?

I knew you could do that ... GE will show True North based on the Geosphere ...

Its funny that last few days I found out you can also derive altitude on Google Earth ...

 

[N017RW]

Article filter

www.ordnancesurvey.co.uk

 

[solentlife]

There are actually many norths due to man navigates in many different locations and conditions. My Father was involved in BOAC doing the pioneer trans Polar flights - I still have his manual computers he used, he was the CAA representative on the flight deck with the crew. Because trans polar means there is no way to use North as we know it - they used a transferred Grid North which basically provides a reference point. Obviously thyere is far more to it than that ... but I think you get the idea.

When I had my land Surveyed for the building of my large workshop / garage - I asked the Topo people to give me two versions. First the usual topographic referenced survey map and a pure GPS position stated map. Why ? So I can later find the reference points myself using my own GPS equipment - which I have a number of. I have rough ground to one side and the markers soon disappear.

Back to OP request ... the customers North is important to know which he wants ...

 

[solentlife]

Please note that Ordnance Survey and similar Bodies have that Grid North which is basically not much use to as its a referencing for their charts and overlays.

The general are : Compass +/- Deviation -> Magnetic +/- Variation -> True North

 

[BudWalker]

Thank you for you answer,
But I am looking for specific number of the tolerance of the compass.
For example if I am telling the drone to take a picture from 90° relative to the north, how much it is accurate.
We are talking about tolerance of 1-2 degrees or 10-20

Your best bet is to use Google Earth to determine where you want to shoot from.

 

[BudWalker]

That's fine but it references to what the Compass see's as its determined Compass to Magnetic North.

If the OP can live with not having exact True North as ZERO and use the angles to select +5 .. +10 etc. then if you can display what the compass output is ... maybe that's good enough ?

Yaw is based on True North.

 

[solentlife]

Yaw is based on True North.

Yaw is the level rotation of a vehicle such as aircraft / boat etc. Please explain where you get YAW is based on True North ?

Yaw doesn't care ... all it is, is a level rotation about an axis ... as in using rudder on an aircraft or putting the left stick to side ...

 

[bsartist]

Here's some sample compass data from a slow turning flight (highlighted in green).
It shows that the compass is measuring to 0.1°

I'm not sure how knowing that makes any difference even if you could find a way to display the heading while you fly.
Because the camera has a very wide angle lens a difference of +/- 5° wouldn't even be noticed.

That would be precision. Not accuracy. ;-)

 

[BudWalker]

Yaw is the level rotation of a vehicle such as aircraft / boat etc. Please explain where you get YAW is based on True North ?

Yaw doesn't care ... all it is, is a level rotation about an axis ... as in using rudder on an aircraft or putting the left stick to side ...

The Yaw values scale is aligned with True North. If Yaw = 0° then the AC is pointing true north. That's assuming that 1) the AC has acquired enough sats to know it's position and 2) the compass is calibrated.

 

[sar104]

Yaw is the level rotation of a vehicle such as aircraft / boat etc. Please explain where you get YAW is based on True North ?

Yaw doesn't care ... all it is, is a level rotation about an axis ... as in using rudder on an aircraft or putting the left stick to side ...

It sounds like you have misunderstood the meaning of the yaw value used by the flight controller. It's the angle between the horizontal projection of the aircraft x-axis and the direction of true north. It's therefore the aircraft's true heading.

 

[solentlife]

It sounds like you have misunderstood the meaning of the yaw value used by the flight controller. It's the angle between the horizontal projection of the aircraft x-axis and the direction of true north. It's therefore the aircraft's true heading.

Sorry but wording it in technical sounding jargon does not change the fact that YAW is purely a horizontal rotation and only has a numerical factor when referenced.
Your last post now uses the the term YAW VALUE .... which agrees with this.

YAW is a indeterminate horizontal rotation

YAW VALUE or number of degrees YAW is a YAW with a numerical addition.

As to being referenced to True North. I agree that the Flight Controller via IMU and Compass, arrives at an approximate True North reference to give a degrees value to its heading.
But Yaw value in fact can be based on any value of the 360.

??

Lets take a P3 / P4 that is heading 000 (North) and yaws -30 ... it now has applied a YAW VALUE of -30 and is heading 330.
Now lest assume the P3 / P4 is now heading 010 ? The YAW VALUE that was applied was +40 ...
Take any heading and cause YAW ... read of the new heading and the difference of the two is YAW VALUE.

Where is True North in that ? The only function of North is to provide a reference 000 for direction. If I said to you - I YAW'd 60 degrees ... are you then going to tell me my new heading is 060 ? Even though I never told you what my original heading was ?

The OP asked what accuracy and how to FLY specific headings ... which is only possible to an approximate accuracy in terms of actual True North, regardless of how many decimals flight log shows.