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New to Spark - confused about loss of signal and auto land

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Jan 9, 2019
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38
Hi everyone,

New to Spark and to this forum. I'm loving the Spark so far. It's my 3rd drone and it's just amazing.

I am confused though why the Spark goes for a slow auto land when a loss of signal happens. If it has adequate battery, shouldn't it start it's trip home? I was starting to use the real controller this week, and I didn't have it synced right. I turned off the phone's wifi, which it was connected to, and the Spark immediately went in to loss of signal. It was a race for me to run across the field to catch it before it landed itself in high grass.

Should it be landing itself straight down? Seems scary if the drone is over a hazardous area.
 

PhantomFandom

Active Member
Join
Jan 1, 2019
Messages
40
Loc
Philadelphia
Hi everyone,

New to Spark and to this forum. I'm loving the Spark so far. It's my 3rd drone and it's just amazing.

I am confused though why the Spark goes for a slow auto land when a loss of signal happens. If it has adequate battery, shouldn't it start it's trip home? I was starting to use the real controller this week, and I didn't have it synced right. I turned off the phone's wifi, which it was connected to, and the Spark immediately went in to loss of signal. It was a race for me to run across the field to catch it before it landed itself in high grass.

Should it be landing itself straight down? Seems scary if the drone is over a hazardous area.
Yes it can and should return to the home spot depending on several factors:
  • Are you sure it had adequate battery power? If it hit the critical low level then it would just land in its current location.
  • In DJI Go, do you have it set to return to its home location when RTH is triggered? Perhaps it is set to land in current location?
  • When you took off, did you wait for GPS lock and did it register its home location? If it did not register its home location then it would have nowhere to go other than straight down.
 
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Spark 317

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Jul 10, 2017
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Indiana, USA
Hi everyone,

New to Spark and to this forum. I'm loving the Spark so far. It's my 3rd drone and it's just amazing.

I am confused though why the Spark goes for a slow auto land when a loss of signal happens. If it has adequate battery, shouldn't it start it's trip home? I was starting to use the real controller this week, and I didn't have it synced right. I turned off the phone's wifi, which it was connected to, and the Spark immediately went in to loss of signal. It was a race for me to run across the field to catch it before it landed itself in high grass.

Should it be landing itself straight down? Seems scary if the drone is over a hazardous area.

RTH Flow chart.
 
Join
Jan 9, 2019
Messages
13
Age
38
Yes it can and should return to the home spot depending on several factors:
  • Are you sure it had adequate battery power? If it hit the critical low level then it would just land in its current location.
  • In DJI Go, do you have it set to return to its home location when RTH is triggered? Perhaps it is set to land in current location?
  • When you took off, did you wait for GPS lock and did it register its home location? If it did not register its home location then it would have nowhere to go other than straight down.
Thanks for the info. It was over 90% battery left when the signal was lost. I always wait for GPS lock and ensure home point is set. It's supposed to come back to me at 98ft AGL. At the very least, it should hover in place right with a healthy battery? If you can't RTH, then stay put. Instead if decided to slowly descend to a landing.
 

PhantomFandom

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Jan 1, 2019
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Philadelphia
Thanks for the info. It was over 90% battery left when the signal was lost. I always wait for GPS lock and ensure home point is set. It's supposed to come back to me at 98ft AGL. At the very least, it should hover in place right with a healthy battery? If you can't RTH, then stay put. Instead if decided to slowly descend to a landing.
Well it should, depending on the settings, so that's why I asked what you had everything set at.
 

PhantomFandom

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This is super helpful! It was further than 9ft horizontal, but maybe the GPS accuracy was far enough off that it felt the need to land? I know from flying real planes that best accuracy is always down to around 30ft.
You said you had to run across the field to catch it so I thought it was definitely farther than 3m from you. Yes GPS can be off somewhat but generally not that much with a good GPS lock.
 
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You said you had to run across the field to catch it so I thought it was definitely farther than 3m from you. Yes GPS can be off somewhat but generally not that much with a good GPS lock.
Appreciate the info. From now on for testing, I'll hover it right next to me or take it further away after RTH is set. i typically see like 10-12 satellites and confirmed ready with GPS lock and the audio confirming RTH has been updated.
 

twickers14

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Sep 6, 2018
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Hi. Can’t add much more but UAV Forecast, my goto app for flying conditions, seems to say “Not good to fly” if there are fewer than 12 sats. Just a thought.
 

Barbara

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Dec 25, 2018
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Algoma District, North Shore, Ontario
Here's a little snipit from DJI's Guide

How to use DJI’s Return to Home (RTH) Safely

Again it’s worth noting that the Spark is a little bit different with how DJI’s Return to Home operates. When the Spark’s RTH is triggered, if the drone is between 3 meters to 20 meters from its home point then the drone will just land automatically with the RTH at Current Altitude option disabled (the default setting in DJI GO 4). If the option is enabled, then the Spark will not ascend if already at the height of 2.5m or more, but if below 2.5m then it will ascend to 2.5m during its RTH. Finally, if the Spark is more than 20m meters away, then it’ll ascend to the set RTH height before heading back home.

Link to the full guide: Click here
 
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PhantomFandom

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Hi. Can’t add much more but UAV Forecast, my goto app for flying conditions, seems to say “Not good to fly” if there are fewer than 12 sats. Just a thought.
That's because it is the default setting. You can choose yourself how many satellites you want to use as the threshold.
 
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That's because it is the default setting. You can choose yourself how many satellites you want to use as the threshold.
Really? Seems odd you'd need over 3 to be honest. I know using real GPS units in the plane, once you have triangulation on 3 satellites it's locked and ready to go.

I may change this down the road, but it seems it finds 12 easily within 30sec or less. What do you recommend?
 

Barbara

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Dec 25, 2018
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That's because it is the default setting. You can choose yourself how many satellites you want to use as the threshold.
Can you? That might be advantageous. I haven't found that option myself yet, or actually any menus for GPS settings other than RTH options. Would love it if you could show where DJI has hidden this, thanks.
 

twickers14

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So what happens if RTH clicks in, perhaps due to loss of signal or poor GPS, and it is 19mtrs away and at 2.5mtrs and there is a big tree between you and craft? Does it crash into the tree? If so can you override the RTH (presume not as craft has lost contact with RC and GPS)?
 

PhantomFandom

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Really? Seems odd you'd need over 3 to be honest. I know using real GPS units in the plane, once you have triangulation on 3 satellites it's locked and ready to go.

I may change this down the road, but it seems it finds 12 easily within 30sec or less. What do you recommend?
The single engine planes I flew did not have GPS in the cockpit so I can't comment definitively on your comment about 3 satellites to get a lock. I do know that you need at least 4 mathematically to pinpoint your position in 3-D space. 3 satellites would only give you a position in 2-D space. Depending on where you are, you "could" make an educated guess with only 3 satellites in 3-D space because one of the two points could end up being way out in space or inside the earth.

Either way I can't conceivably see how a GPS that is approved for navigation in the cockpit, can be used with only 3 satellites. What happens when you have transmission errors? What happens when one satellite moves out of view? I think you need just as many (and likely more) satellites when using a GPS for navigation in the cockpit, as you do when flying a drone.

Each person obviously has their own comfort level and preferences. I have my threshold set at 10. If it's less than 10, I would make a determination on the fly. I would consider 7 a bare minimum. I would fly with fewer (or none) if I knew I was doing strictly ATTI mode flying in close visual range and low wind.
 

PhantomFandom

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Can you? That might be advantageous. I haven't found that option myself yet, or actually any menus for GPS settings other than RTH options. Would love it if you could show where DJI has hidden this, thanks.
No, not in the drone settings. I was talking about in UAV forecast since that is what @twickers14 was talking about.
 

PhantomFandom

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So what happens if RTH clicks in, perhaps due to loss of signal or poor GPS, and it is 19mtrs away and at 2.5mtrs and there is a big tree between you and craft? Does it crash into the tree? If so can you override the RTH (presume not as craft has lost contact with RC and GPS)?
That's a whole lot of "IF" there. If the Spark loses contact with your controller but DOES have GPS reception then it should initiate the proper procedure based on where it is, according to the flow chart

If the Spark loses GPS coverage but still has link to your controller, it should not initiate RTH. It should just switch to ATTI mode and leave you to control it properly.

If the Spark loses GPS coverage and loses link to the controller then I believe it will just hover in place since it cannot find its way home. If it then hovers long enough to reach critical battery level, it would land in place.

On a RTH the Spark should avoid obstacles based on settings you set in DJI Go 4 and the ability of the sensors to see those objects properly. That is of course unless the sensors are off (i.e. if you are flying in Sport Mode).

As I said, there are a lot of different options.
 

twickers14

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Thanks really helpful. We’re so persona non grata here in the UK at the moment it will be a while before I can fly without disapproving looks. Live in a City but with lovely open downs up the road which are popular with dog walkers. Hey ho!
 

Barbara

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Dec 25, 2018
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Algoma District, North Shore, Ontario
No, not in the drone settings. I was talking about in UAV forecast since that is what @twickers14 was talking about.
Okay, thanks for clearing that up. I find the DJI manuals a bit confusing at times as they cover a wide variety of product, and the online manual for the GO 4 App is a pain in the....
 

Bob Johnston

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May 2, 2018
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What hasn't been mentioned (I dont think) is that the ac lands in place if rth is initiated within 3-20 meters of home point.
 

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