RTH without GPS

[mertsendag]

Hi folks,

I was wondering what would happen in the following case:
• Spark has GPS lock and records home point successfully before takeoff
• While in the air, it loses quality GPS signal and enters OPTI mode (which actually does happen)

Will it still be able to return to home point?
If not, doesn't this make flying dangerous as in case of GPS signal loss, we are going down? In that case, RTH is good only in cases of RC connection loss?

Regards

 

[charliespark]

Without GPS there is no RTH as Spark does not know where it is! It will hover where it is. That's why it is important to become proficient in Atti mode so you can bring your SPARK home manually.

 

[Spark 317]

As charliespark has mentioned, it won't know where home is, but if a GPS lock is re-established, I'm pretty sure the Home Point is still there and the Spark knows how to get home.
I've had luck by actually gaining altitude and getting the lock back when flying around hills and trees.

But if it stays in Atti-mode, you are controlling it so keep an eye on the Spark and your telemetry to bring it home.

 

[twickers14]

Atti mode is basically manual mode yes? No GPS so you control everything?

 

[Spark 317]

Atti mode is basically manual mode yes? No GPS so you control everything?

Yes.

The Spark should maintain it's altitude but will drift with the wind.

That's why it is good to check the UAV FORECAST app and see the wind direction and orientation of the Spark when flying manually.
Another useful app is WINDY. Real time wind direction and speed.

If you don't have a visual on the Spark, pay attention to the telemetry on the screen if you reestablish a GPS lock.
Numbers getting bigger= Spark going away from you.
Smaller numbers = getting closer.

 

[mertsendag]

Without GPS there is no RTH as Spark does not know where it is! It will hover where it is. That's why it is important to become proficient in Atti mode so you can bring your SPARK home manually.

Does all this mean that if I lose RC connection somehow, and the aircraft loses GPS signal, there is no way for it to come back?

 

[Spark 317]

Does all this mean that if I lose RC connection somehow, and the aircraft loses GPS signal, there is no way for it to come back?

Yep.

If you lose the Spark, that's where the flight logs come into play to help figure out where it went.

If in Atti-mode at it's last known GPS signal, it will drift with the wind until it hits the critical low battery and will land wherever it's at.

With detailed local weather reports you may be able to make a search area with the information at hand.

Battery time left, wind speed and direction will help in establishing a place to start looking.
If the altitude was lower than surrounding obstacles (trees), follow the search line and look up in the trees if it decided to crash or land there.

 

[twickers14]

Yes.

The Spark should maintain it's altitude but will drift with the wind.

That's why it is good to check the UAV FORECAST app and see the wind direction and orientation of the Spark when flying manually.
Another useful app is WINDY. Real time wind direction and speed.

If you don't have a visual on the Spark, pay attention to the telemetry on the screen.
Numbers getting bigger= Spark going away from you.
Smaller numbers = getting closer.

Thanks for this. Very helpful.

 

[Speedmeister]

No GPS means AC in ATTI mode (no GPS hold). It will hover until feedback from RC or until battery runs out and land. Wind will affect its positioning though. It will not hover in place unless it is less than 10 meters in altitude. VPS will take over if it is not blind. Try it inside your house.

 

[twickers14]

No GPS means AC in ATTI mode (no GPS hold). It will hover until feedback from RC or until battery runs out and land. Wind will affect its positioning though. It will not hover in place unless it is less than 10 meters in altitude. VPS will take over if it is not blind. Try it inside your house.

Many thanks.

 

[mertsendag]

This is terrible at the times where it says aircraft disconnected. So in that case if you lose GPS while in the air, you are in big trouble.

 

[NRRTRAINS]

loosing GPS is the main reason to fly in LOS .

 

[Speedmeister]

It is pretty unusual for it to loss GPS on open sky unless it is defective or extreme signal interferences. Always be aware of telemetry information when flying. You can have GPS problem flying between tall buildings or in between valleys. If you see GPS signal dropping then its time to increase altitude.

 

[mha1]

Atti mode is basically manual mode yes? No GPS so you control everything?

No, with losing GPS the system only loses the ability to hold a position steadily and to navigate to a given position (home point) on its own. All other sensors like IMU (3-axis accelerators, 3-axis gyros), Baro (barometric altitude) are still working and are used to assist you in your piloting task.

Atti is still a heavily assisted flight mode using IMU and baro data to support you with self leveling the drone and maintaining a steady altitude. In a pure manual mode you'd loose the self leveling and alt hold ability degrading to a flight mode race quad flyers love (Manual or Acro). So no panic if it reverts to Atti mode. One side effect of not being able to hold a steady position though is drift. Your drone will drift with the wind if you don't counteract the motion with pitch and roll inputs. Apart from this you won't notice a huge difference in flying the drone. Push the stick forward and the drone will pickup speed and fly to where the nose is pointing. Release the stick it will stop, self level and hover happily drifting with the wind. Think you get the picture. One other important aspect: losing GPS does not affect your RC link and video link.

So what do you if your drone reverts to Atti and you still have a good visual:
- don't panic, it won't fall out of the sky immediately
- don't think RTH will save you. Man up.
- Turn it by using the yaw stick until you see the back of the drone
- Pull the the pitch stick moderatly back to fly it towards you
- If it drifts off course due to wind apply some roll inputs

If you lost visual there is still hope:
- don't panic, it won't fall out of the sky immediately
- don't think RTH will save you. Man up even more and fight.
- Use your video link. Turn the drone by using the yaw stick until you identify some known ground reference points.
- Fly by your screen. Don't give up!

If you lose GPS and your video link with the drone out of sight at the same time you are in a double failure mode which should statistically be rare. And you are doomed. Think about staying in LOS or at least video range with lots of margin for errors for the next flight after buying a new drone. Remember, even bad experiences make you a better pilot.

Too bad DJI doesn't allow Spark customers to practice Atti mode in order to demystify it.

 

[Dodge DeBoulet]

- If you can't identify any ground reference points apply a small amount of forward pitch and check the distance indicator. If it increases turn the drone 180 degree. Fly by your screen and instruments. Don't give up!

How does the distance indicator calculate the distance if GPS is lost?

 

[Spark 317]

How does the distance indicator calculate the distance if GPS is lost?

Huh.
Good point.

 

[mha1]

How does the distance indicator calculate the distance if GPS is lost?

It can't be calculated. I got carried away. Text corrected.

 

[charliespark]

Does all this mean that if I lose RC connection somehow, and the aircraft loses GPS signal, there is no way for it to come back?

probably but it is a very unlikely senario if you are obeying the drone 'rules'

 

[Stephen]

No, with losing GPS the system only loses the ability to hold a position steadily and to navigate to a given position (home point) on its own. All other sensors like IMU (3-axis accelerators, 3-axis gyros), Baro (barometric altitude) are still working and are used to assist you in your piloting task.

Atti is still a heavily assisted flight mode using IMU and baro data to support you with self leveling the drone and maintaining a steady altitude. In a pure manual mode you'd loose the self leveling and alt hold ability degrading to a flight mode race quad flyers love (Manual or Acro). So no panic if it reverts to Atti mode. One side effect of not being able to hold a steady position though is drift. Your drone will drift with the wind if you don't counteract the motion with pitch and roll inputs. Apart from this you won't notice a huge difference in flying the drone. Push the stick forward and the drone will pickup speed and fly to where the nose is pointing. Release the stick it will stop, self level and hover happily drifting with the wind. Think you get the picture. One other important aspect: losing GPS does not affect your RC link and video link.

So what do you if your drone reverts to Atti and you still have a good visual:
- don't panic, it won't fall out of the sky immediately
- don't think RTH will save you. Man up.
- Turn it by using the yaw stick until you see the back of the drone
- Pull the the pitch stick moderatly back to fly it towards you
- If it drifts off course due to wind apply some roll inputs

If you lost visual there is still hope:
- don't panic, it won't fall out of the sky immediately
- don't think RTH will save you. Man up even more and fight.
- Use your video link. Turn the drone by using the yaw stick until you identify some known ground reference points.
- Fly by your screen. Don't give up!

If you lose GPS and your video link with the drone out of sight at the same time you are in a double failure mode which should statistically be rare. And you are doomed. Think about staying in LOS or at least video range with lots of margin for errors for the next flight after buying a new drone. Remember, even bad experiences make you a better pilot.

Too bad DJI doesn't allow Spark customers to practice Atti mode in order to demystify it.

I've got a problem with GPS board, won't operate in attic mode, just said can't take off ??