How does the maivc tell the time?

[andykearns]

Hi Guys just a quick one,

Im doing a thesis on the mavic pro and need to determine how the time is stamped onto the image.

I originally presumed it was GPS time, but when i ran the images through an exif viewer the GPS time wasn't there.


Cheers let me know

 

[Mr. Salty]

The DJI Go app picks it up from whatever device you're using to fly it with.

 

[Simmo]

Off your device. A way to prove that would be to set the incorrect time on your device and take a photo.

 

[tcope]

The DJI Go app picks it up from whatever device you're using to fly it with.

I doubt this is the case as the Spark and Air can be flown without an device or controller and the Pro can be flown without a device and only a controller.

 

[tcope]

Off your device. A way to prove that would be to set the incorrect time on your device and take a photo.

Fly without a device and there will still be a time stamp.

 

[tcope]

I suspect it comes from the GPS unit as the GPS unit needs to be _extremely_ accurate. I'm pretty sure GPS sat send their own time directly to the GPS chip in the drone. I'm guessing this is simply converted or read into real world time.

 

[DroneJI]

I suspect it comes from the GPS unit as the GPS unit needs to be _extremely_ accurate. I'm pretty sure GPS sat send their own time directly to the GPS chip in the drone. I'm guessing this is simply converted or read into real world time.

I’m going to agree with from the GPS satellites I know my Garmin gets it from the Satellites and also uses it to set the correct Time Zone.

 

[matth1000]

Every gps sat has an atomic clock. This then gets sent to the device that is using the gps signal, at least that’s what I remember from land surveying school 20 years ago

 

[tcope]

Every gps sat has an atomic clock. This then gets sent to the device that is using the gps signal, at least that’s what I remember from land surveying school 20 years ago

The Earth device keeps time. The sat sends it's own time to the earth device. This allows the Earth device to know it's distance to that sat. Do this with several devices and, using triangulation, the Earth device can know where it is on Earth. All time devices need to be _extreemly_ accurate. So accurate that even the different gravity and speed of the sats need to be compensated for as this changes the time.

But the Earth device needs to keep it's own time.

 

[Qoncussion]

I flew for a while with a dedicated LG-G2 phone that would not retain the time every time it was turned off. Having forgotten on endless occasions to set the clock before a flight, I can say that my .txt logs always had the wrong times showing, but the images and videos on the microSD card from the Mavic had the correct timestamp. So my guess is, GPS.

 

[Cslucas34]

The Earth device keeps time. The sat sends it's own time to the earth device. This allows the Earth device to know it's distance to that sat. Do this with several devices and, using triangulation, the Earth device can know where it is on Earth. All time devices need to be _extreemly_ accurate. So accurate that even the different gravity and speed of the sats need to be compensated for as this changes the time.

But the Earth device needs to keep it's own time.

You are partially correct. The “earth” device you refer to gets its time signal from the same place the satellite does, the US Atomic clock that’s land based. The time code and source has to be the same. To triangulate position you need at least 3 satellites and they simply measure how long it took for the signal to get to the device. But in order to know that, they have to have the same time.. thus they both use the same source, the US Atomic clock. 4 satellites needed for elevation as well as position. Sorry, geeked out a little when I read your explanation. Used to teach this for the military lol.

 

[joshmentele]

Hi Guys just a quick one,

Im doing a thesis on the mavic pro and need to determine how the time is stamped onto the image.

I originally presumed it was GPS time, but when i ran the images through an exif viewer the GPS time wasn't there.


Cheers let me know

The GPS provides time.

 

[Qoncussion]

You are partially correct. The “earth” device you refer to gets its time signal from the same place the satellite does, the US Atomic clock that’s land based. The time code and source has to be the same. To triangulate position you need at least 3 satellites and they simply measure how long it took for the signal to get to the device. But in order to know that, they have to have the same time.. thus they both use the same source, the US Atomic clock. 4 satellites needed for elevation as well as position. Sorry, geeked out a little when I read your explanation. Used to teach this for the military lol.

And, if you want or need to blow your geek mind to shreds (and I'm sure you already know this, as an instructor), GPS clocks must adjust for general relativity. At their speed and altitude, their clocks - if left unchecked - are running at a different speed than clocks on Earth. Clocks move relatively slower at high velocity - in the case of GPS satellites, -7 microseconds/day, but relatively faster in low gravity, +45 microseconds/day. So they adjust by 45-7=38 microseconds/day to maintain relative time for us Earth-bound folks.

 

[Kilrah]

Both app and GPS provide time. If an app is connected the aircraft will know the time before it gets GPS signal, if not it needs to wait. Guess GPS gets priority when available as @Qoncussion 's post above suggests.