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Two RTH Tests
839 26 2017-8-26
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Charles Adams
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Inspired by other forum conversations, I performed two RTH tests today.  All equipment is on latest firmware and software.

First test:  Using only gesture control (no phone no RC), I palm launched, sent the spark away to follow, and walked some distance from my launch location.  The purpose of this test was to determine the behavior of the spark, when using only gesture control, when the batteries ran low.

Result:  The LEDs performed their indication of low battery, and the craft then performed an RTH by elevating to altitude, flying back to the original palm launch location, and descending from there.

Conclusion:  Current behavior (whether or not designed or intended) is that the spark considers the location of palm launch the RTH location.  It does in fact elevate (and could therefore plow into above structures or obstacles).

Question:  Is this the best behavior for this use case?  I don't think so.  I think it should assume that it is within 20 feet of RTH when in gesture mode, and descend in place.
Question:  Does not compass and GPS have impact in this use case?  (That's rhetorical).  Could not environment factors impeed the behavior so much that the craft could be at risk?  I need to review the manual and see if the led lights are indicating successful gps and compass operations.  Otherwise anybody who chooses to fly with gestures in a man-made environment may be taking risks.

Second Test:  Using phone and RC, I launched and set home point.  I then walked and flew a great distance away, and I set home point to location of RC.  I then insructed the craft to RTH.  It behaved as though my current (RC) location was home point, and did not fly back to original home point.  I then performed a second test.  I set home point to craft location, I walked and flew some distance away, I set RC location to home point, I walked and flew away from that location (craft was in a separate location from myself and from any of the prior pre-set home points, and I was in a completely different location from craft or any other home-points).  I instructed the craft to RTH, and it flew back to the most recently set RC homepoint location.

Conclusion:  I couldn't get this RTH functionality to fail.  It behaved as expected and desired in every instance.
2017-8-26
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Charles Adams
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As an additional and unrelated note:  My second test didn't use OTG, it used wifi.  While the wifi connection seems more stable than before, it is still not as stable or as reliable as OTG, and I'll continue to use OTG as my primary Phone to RC connection.
2017-8-26
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Lucas775
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Good to know, I haven't had the chance to RTH on the spark yet all I have been doing is manually hand catching this fun little drone.  Thanks for the info.
2017-8-26
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Montfrooij
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Thanks for the testing. It seems the first behaviour is less well thought through indeed
2017-8-26
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Dirk52
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There is no need for a Homepoint when no device is connected.
Dji, remove the HP for gesture control only.
2017-8-26
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fans9ea9c44f
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When mine displayed low batt lights it landed where it was. So don't try it off edgeof cliff
2017-8-26
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fans9ea9c44f
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Also in gesture after swithing on,if you wait before double tap, 6 quick green flashes of rear lights indicate home point is set.
2017-8-26
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JMR58
First Officer
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Still a pity there is no audio signal for low battery...
2017-8-26
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Charles Adams
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fans9ea9c44f Posted at 2017-8-26 11:06
When mine displayed low batt lights it landed where it was. So don't try it off edgeof cliff

I'm guessing it follows the default RTH behaviors...  if in close proximity to original launch point, it comes down.  If some distance from original launch point, it goes up goes across and then comes down.
2017-8-26
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fans9ea9c44f
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Yes but the main problem is if you wave it away, and it tracks you then loses you, no amount of gesturing at all will reconnect you.
2017-8-26
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OneMatt
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Situation 1: RTH still makes some sense, as there are times when landing in place will be disastrous. Example, if the 20ft away location is out over water or a cliff when taking a dramatic selfie.

What I would suggest, would be if it is currently tracking the user, it should treat the home location as where it sees the user (20ft forward and down, like auto-beckon). This would also work indoors.

At a minimum, when the drone knows it has flown entirely in disconnected mode, it should RTH at the present altitude (20ft), and not ascend.
2017-8-26
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fans5d9349b7
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JMR58 Posted at 2017-8-26 12:45
Still a pity there is no audio signal for low battery...

Would you hear it over the blade noise?
2017-8-26
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ImHereToCrash
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fans5d9349b7 Posted at 2017-8-26 13:57
Would you hear it over the blade noise?

hah.. definitely it comes out of the controller... as a mavic user i think low battery beeping is ideal for the spark, but is just annoying as all hell on mavic because a low battery is still sometimes like 10 minutes..basically the entire runtime of a dji spark battery..
2017-8-26
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LouisP
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Thanks....  I have been slowly trying out all the features of the spark one at a time. RTH is my next test.. :-)
2017-8-26
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Spaners
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More intresting stuff that dji should have put in a manual
good work Charles
2017-8-26
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R&L Aerial
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Dirk52 Posted at 2017-8-26 11:01
There is no need for a Homepoint when no device is connected.
Dji, remove the HP for gesture control only.

As others have stated home point is useful in gesture mode, if standing on a dock over water you want the spark to come back to the dock, not land 10 feet away?
2017-8-27
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Dirk52
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R&L Aerial  Posted at 2017-8-27 07:25
As others have stated home point is useful in gesture mode, if standing on a dock over water you want the spark to come back to the dock, not land 10 feet away?

He won't come back when it's only 10 feet away.
The normal failsafe options like on the other Dji drones would also be okay.. Land, Hover or RtH. But just RtH is the worst solution. You can't track yourself safe in an area where the Spark is not allowed to rising up.

DJI, why you are not activating these options?
2017-8-27
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Indi91
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Thanks for sharing!
2017-8-28
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TranceMist
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I have performed these tests as well and my conclusion was that it all works well under good conditions.
I also now carefully plan my takeoff point and set RTH altitude accordingly to make sure I'm clear enough of any trees or other obstacles.

It's the edge cases that I worry about. Aircraft encountering compass interference while flying, high KP index affecting GPS lock and high contrasts affecting obstacle avoidance on RTH (which I have had prevent my Spark from returning on RTH causing me to take over manual control: http://forum.dji.com/forum.php?mod=viewthread&tid=110072)
2017-8-28
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Sparky_17
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Thanks for posting this .. this is great information and seems to work as expected.
2017-8-28
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DJI Susan
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Dirk52 Posted at 2017-8-27 23:26
He won't come back when it's only 10 feet away.
The normal failsafe options like on the other Dji drones would also be okay.. Land, Hover or RtH. But just RtH is the worst solution. You can't track yourself safe in an area where the Spark is not allowed to rising up.

I agree with R&L Aerial. The take-off point is considered as the safe point. Landing to water is always a catastrophe.
2017-9-3
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Dirk52
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DJI Susan Posted at 2017-9-3 23:22
I agree with R&L Aerial. The take-off point is considered as the safe point. Landing to water is always a catastrophe.

With Wifi only I can't check the Homepoint on the map -> no map available. So I can't be sure wether it is correct or not.
I can't change the Failsafe settings to hover, so I can't track my self in an area where the spark should not rising up.
I can't track myself for a distance longer than 50m.

If you ask me, remove the HP when no device is connected and you can use the Spark as it is supposed to.
Or add more Features to the go app like hover or land for failsafe. Also a dynamic when no device is connected that is based on the tracked Person would be helpful.
2017-9-3
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HrMelin
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I don't see the problem about the spark elevating during RTH. In the ac settings under rth setting it is possible to activate rth in current altitude.
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2017-9-4
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Dirk52
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HrMelin Posted at 2017-9-4 00:00
I don't see the problem about the spark elevating during RTH. In the ac settings under rth setting it is possible to activate rth in current altitude.

I see a lot of porblems... example:
You track youself on a way with trees on both sides. The way is not straight, it got some curves. No the spark want to rth..on the direct way to the hp. What do you think will happen?
We need the option to let the spark land or hover for failsafe.. Phantom, Mavic, Inspire..all got these features.
2017-9-4
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HrMelin
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Dirk52 Posted at 2017-9-4 00:07
I see a lot of porblems... example:
You track youself on a way with trees on both sides. The way is not straight, it got some curves. No the spark want to rth..on the direct way to the hp. What do you think will happen?
We need the option to let the spark land or hover for failsafe.. Phantom, Mavic, Inspire..all got these features.

I see your point in regards to curvey hallway off trees then it is no good
2017-9-4
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DJI Susan
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Dirk52 Posted at 2017-9-3 23:41
With Wifi only I can't check the Homepoint on the map -> no map available. So I can't be sure wether it is correct or not.
I can't change the Failsafe settings to hover, so I can't track my self in an area where the spark should not rising up.
I can't track myself for a distance longer than 50m.

Due to the virtual sticks and limited screen size, the map is not available when connecting mobile only. Active track might be helpful for the feature you described.
2017-9-5
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Dirk52
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DJI Susan Posted at 2017-9-5 02:29
Due to the virtual sticks and limited screen size, the map is not available when connecting mobile only. Active track might be helpful for the feature you described.

Maybe you can explain me the difference in the behavior when I use active track instead of the tracking after the away and follow gesture?
I got in both modes no map, a very short tracking distance and in case of failsafe the spark will rth and not hover. Or am I wrong?
2017-9-5
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