Lost my P3A in the drink!

[Meta4]

Lots of replies are guesses. And the antenna is not directional.

I don't know how to make this any clearer. I have tested it and the GPS antenna is directional.
Go and try for yourself instead of guessing.

 

[Wessex]

Mine reads the same here. If the antenna was directional it wouldn't read upside down. The satellites are over a vast area of the sky. The antenna needs to receive from all available and that is over a 180 degree area. Hence none directional.

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[Wessex]

I'll leave it to you to solve folp's query.

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[Meta4]

Mine reads the same here. If the antenna was directional it wouldn't read upside down. The satellites are over a vast area of the sky. The antenna needs to receive from all available and that is over a 180 degree area. Hence none directional.

If the antenna is not directional .. then it's a case of reception from the sky being blocked by the internals of the Phantom when it's upside down.
It's common to see the GPS sat numbers falling when a Phantom is tumbling and checking with mine produces the same result.

 

[Wessex]

You don't understand Radio signal transmission/reception.

GPS Antenna:

They are Omnidirectional by design. The more satellites you receive, the greater the known precision of your location. That is the number you see changing, that locates your position within "X" number of meters.

Since More satellites provide greater precision of your location, and the satellites are constantly moving, and the greatest precision comes from the satellites farthest from you (nearer the horizon), the antenna has to be omnidirectional to cover 360 degrees of the sky.

Some antennas are designed to be in a plane (flat and 2 dimensional) and others may be long and rod shaped, they are still Omnidirectional.

Look it up on Google. Don't confuse satellite dishes for receiving satellite TV or telephone signals with the antennas used to receive gps Radio signals


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[folp]

hi all -

thanks for all the input I was viewing the healthy drones report and it looks like I may have hit a bird. at 12' 5" the compass started going crazy, so I'm guessing something sent it into a free fall. the small consolation here is that I bought a used drone knowing something like this could happen

thanks again, this forum is pretty amazing!

mike

 

[Wessex]

One of those moments where you have to draw a line and move on Mike. It could have been a bird or a prop disintegrating: not unheard of.

I had a crash: using Ultimate Flight app and a P3S it was on a waypoint mission to orbit a tower. Took off and then announced the recording had stopped. Took my eye off of the ball and as it went behind the tower I heard a crash. Ran round the other side to find it on it's back with the camera dented and at a funny angle. Fallen approx. 60 feet. At over £200 for a replacement camera I decided to purchase a new A/C. Still got the old one minus the camera for teaching my grandson how to fly it. Can't blame anyone or anything, I should have checked the flying radius.

Ess Aitch One Tee happens.

 

[Meta4]

You don't understand Radio signal transmission/reception.

And you haven't taken in anything I wrote.
btw .. I've been using GPS professionally for 20 years and have a reasonable idea of how it works.

Looking at the data, it's clear that loss of GPS sats is a symptom of a falling and tumbling Phantom and not the cause.
The Phantom loses sat numbers after it starts to fall - not before.
And losing sats doesn't make a Phantom fall.

There's no need to come up with far fetched, imaginary phenomena when a simple explanation fits the data better.

 

[FLBoyZ06]

Jamming GPS is a method of countermeasure, loss of GPS signal was noted.

No. You're not looking at this correctly. Every ship in that area of Oakland is using a GPS to safely navigate the channels there. Every ship pilot is using some type of ECDIS that is dependent on a GPS signal for ship position. Of all areas, there is no GPS jamming here ever.

Probably hit something in the air, a bird or something. Breaks the prop and sends it tumbling and that's where you lose the GPS.

 

[HitFactor]

Your right jamming ships GPS would be a catastrophe. A focused beam, short duration, aimed at a drone would easily confuse the GPS and maybe other sensors. I'm almost certain I read about this as an anti-uas measure.

 

[tevek]

Well this has been an interesting thread with a variety of suggestions for the OPs loss of his drone. I must admit my time in the military on war ships using various means of warfare countermeasures and the extensive use of GPS suggests that not everyone is onboard with how it works. As the OP suggested as others have, it is possibly a simple bird strike and nothing else.

 

[FLBoyZ06]

Your right jamming ships GPS would be a catastrophe. A focused beam, short duration, aimed at a drone would easily confuse the GPS and maybe other sensors. I'm almost certain I read about this as an anti-uas measure.

Coming from a maritime background and have sailed out of Oakland on American Flagged container ships from nearly those berths in the photo early in the thread I don't see the reasoning behind it. I understand that a focused beam could have been used but the terminal operators and shipboard operations aspect have no interest in a drone flying out over the water or even over the terminal. But this given location is heavily ship based operations on the north side of the channel and then on the south side you have the old airport that the Mythbusters were using.

 

[NHCarl]

I am totally new to DJI, in fact have yet to fly my P3P due to winter in NH. However, suspect a hardware failure could possibly be to blame. Broken prop, motor failure, ESC failure, etc. Really sorry for the loss of your aircraft though. I know I would be totally bummed!

 

[folp]

Hi all -

I want to say thanks again for everyone's input, this forum is an invaluable resource. My plan is to get a P4Pro (or P5?) when I have the $$$. In the meantime however, if anyone is interested, I'm selling my remaining gear: Lost my drone in the Oakland Harbor, so I guess I don't need these anymore :(

Hope to be flying again soon

Cheers!

Mike

 

[dwallersv]

You are entitled to your thoughts but if you offer outlandish guesses, expect to be corrected.

Fair enough, and you did correct his misunderstanding.

However, "outlandish" is purely an opinion, and a rather denigrating one at that. While I understood well the technical details you were drawing upon, I'm an EE. Most people are not, and in fact most do not understand these details.

You are being uncivil. You could contribute much more the general community if you were friendly and patient with otherwise innocent fellow members when educating them about these interesting technologies. They're much more likely to focus and remember, rather than feeling offended and drawing their own opinions about you.

 

[dwallersv]

The GPS receiver isn't directional. It will receive just as well upside down as well as the correct way up.

Actually, it is, but not for the reasons you may think.

The antenna is not a directional design. However, when the aircraft is upside-down the battery and battery compartment are in between the antenna and most of the sky. The metal ions in solution in the battery are an exceptional shield for electromagnetic radiation, particularly at microwave frequencies (GPS signals). The metal battery compartment adds more attenuation to the signal.

So, while the design itself is not strictly directional, operationally it ends up being that way. This is why when a Phantom tumbles, it loses satellite fixes.

 

[pomonabill220]

They are Omnidirectional by design.

But since there is a shield over the GPS receiver internally, when the antenna is "looking" at the ground, it will not receive any sat. signals as they are being shielded.

 

[Wessex]

@dwallersv thank you for the reply to meta4. As a moderator I was disgusted with his response.
I do know what I'm talking about. I am a licenced radio operator (G4TMF) and an electrical engineer.
If the assumption that the battery is going to shield radio signals from reaching the receiving antenna on the drone then ask yourself why the drone will still receive radio signals inside a building? Not just drones but mobile (cell) phones and SatNav units. These also receive radio signals from satellites whilst inside of the automobile and that is an environment surrounded by a metal shell.
I mentioned initially that the loss of gps signals switching the unit to ATTI mode would not have caused the craft to have suddenly drop because of internal barometers would maintain it's height.
The main clue to the fact that the craft flipped is in the speed increase prior to hitting the water. Why it flipped no one knows. A few have posted suggestions but to accuse my suggestions as outlandish is not worthy of reoly.
I have studied gps technology and I understand it. End of.


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[Meta4]

The main clue to the fact that the craft flipped is in the speed increase prior to hitting the water. Why it flipped no one knows. A few have posted suggestions but to accuse my suggestions as outlandish is not worthy of reoly.
I have studied gps technology and I understand it.

Then perhaps you can explain why ....
When I turn my Phantom over, holding it by one arm, the sat number drops 50%.
I've tested this and it's consistent.
I've also noted dropping GPS numbers in many of the falling-from-the-sky incidents I've investigated.
I'd thought this would be because:
The Phantom GPS antenna has a shield under it to protect the GPS from interference from the internal circuitry of the Phantom.
The battery and possibly the metal section of the underbody would also add to the GPS signal blocking when the Phantom is upside down.

And .. the notion of a busy port and public waterway being "protected from drones by GPS jamming as was suggested in the thread is fanciful nonsense.

 

[Wessex]

And .. the notion of a busy port and public waterway being "protected from drones by GPS jamming as was suggested in the thread is fanciful nonsense.

At least we agree on something. However I didn't post that comment.

Peter

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