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Altitude for RTH if I set a new Home Point during flight

ErikBad

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If I set a new Home Point during flight - does the MM know the altitude of that home-point? If not, I can see scenarios where it flies into trees, mountain walls or obstacles during a RTH-process, due to the fact that it is missing data for the altitude of the new Home Point. Am i right?
 
A good question, easy enough to check but not in the dark and rain lol.
That said, sometime ago I did a midair motor stop and restart with a Phantom 3 the indicated height in the txt recorded after the restart was relative to the original launch point.
So, I think your thinking is correct and the ceilings remain relative to the original launch point.
 
@ErikBad the RTH height is based on where it took of from ,so if you landed and then flew up from another home point then the RTH height would be based on the new take off point
if you just changed the home point in the app,while you were flying then the drone would still do its RTH at the height you set at the first take off point it only knows its height relevant to where it took off from it has no idea how high it is relative to the ground beneath it as it flies over changing elevations ,when it is at 30ft or less then the downwards sensors come into action and then the drones altitude is pretty accurate relative to the ground below it
 
...the RTH height is based on where it took of from... if you just changed the home point in the app,while you were flying then the drone would still do its RTH at the height you set at the first take off point...
That's correct ... this as the HP height are only reset if the barometric sensor is reset, & that only happens at a take off.

This is easily seen in the mobile device DAT log just after take off ... here an example from one of my own logs.

1612479146484.png
 
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does the MM know the altitude of that home-point? If not, I can see scenarios where it flies into trees, mountain walls or obstacles during a RTH-process, due to the fact that it is missing data for the altitude of the new Home Point. Am i right?
Home points are two-dimensional.
They have no altitude associated with them.
 
Home points are two-dimensional.
They have no altitude associated with them.
Interesting
Are there any negatives in setting the homepoint in flight? I always wait for sufficient sats before takeoff, which i assume sets the homepoint too
 
Interesting
Are there any negatives in setting the homepoint in flight?
Do you have any specific reason to reset the homepoint?
One potential negative is inadvertently resetting to a bad location for an RTH autolanding.
But if you aren't moving far from the launch point and your launch point is out in the open, there's really no need at all to be resetting your home point.
I always wait for sufficient sats before takeoff, which i assume sets the homepoint too
What's sufficient?
You don't know because there's no single magic number that's "sufficient".
Don't assume anything, wait for the flight controller to determine that the GPS location data is good and record the home point for you.
 
Do you have any specific reason to reset the homepoint?
One potential negative is inadvertently resetting to a bad location for an RTH autolanding.
But if you aren't moving far from the launch point and your launch point is out in the open, there's really no need at all to be resetting your home point.

What's sufficient?
You don't know because there's no single magic number that's "sufficient".
Don't assume anything, wait for the flight controller to determine that the GPS location data is good and record the home point for you.
Reasons for resetting the homepoint during flights: I'm thinking that resetting your homepoint during flight is useful if you are moving (walking/skiing/cykling etc) while flying the drone, you might not want to return to the original take-off spot if there is a RTH-procedure. Or if you are surprised by strong winds during the flight session, and the drone struggles to return to the original homepoint due to strong headwind.
But I'm a complete newbie, so I'm sure you can give me some good input on this matter!
Cheers
 
...resetting your homepoint during flight is useful if you are moving (walking/skiing/cykling etc) while flying the drone, you might not want to return to the original take-off spot

...Or if you are surprised by strong winds during the flight session, and the drone struggles to return to the original homepoint due to strong headwind.

Well ... for the first alternative I think I rather would go for Return to controller, most mobile devices today have GPS builtin so that should work, & then periodically reset it if constantly moving (as reset to controller is to present position & not follow controller). The main purpose is to get the AC within control distance, not let it land on uncharted ground... take control & fly it all the way to you & land manually.

The second purpose is actually a bit of a clever idea ... usually during a blow away it's the AC-RC disconnect that finally makes the AC disappear to be never seen again. Usually the connection is lost no matter if the pilot tries to lose height, tries to actually land on the spot or hope that the RTH will fix it back home up wind. In all cases the connection is most probably lost & the AC execute the failsafe action, rises up & continue to be blown away until the battery is depleted & low battery force landing happens at some unknown position. But if resetting the HP a good distance down wind the AC will commence RTH with the wind & the chances that it actually will land in a relative known position is high ... then you can go there & pick it up.
 
Well ... for the first alternative I think I rather would go for Return to controller, most mobile devices today have GPS builtin so that should work, & then periodically reset it if constantly moving (as reset to controller is to present position & not follow controller). The main purpose is to get the AC within control distance, not let it land on uncharted ground... take control & fly it all the way to you & land manually.

The second purpose is actually a bit of a clever idea ... usually during a blow away it's the AC-RC disconnect that finally makes the AC disappear to be never seen again. Usually the connection is lost no matter if the pilot tries to lose height, tries to actually land on the spot or hope that the RTH will fix it back home up wind. In all cases the connection is most probably lost & the AC execute the failsafe action, rises up & continue to be blown away until the battery is depleted & low battery force landing happens at some unknown position. But if resetting the HP a good distance down wind the AC will commence RTH with the wind & the chances that it actually will land in a relative known position is high ... then you can go there & pick it up.
I see you points. But as I fly Mavic Mini 1 using DJI Fly, i don't think I have the function "Return to controller". But I guess I could just (continuously) update the homepoint to a spot really close to me and my controller, as shown in the map when I update the homepoint.
Learning in process, thanks for the input!
 
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You do, there are 2 symbols in the options, 1 is for the Drone the other is for the controller. You can also set "somewhere on the map" as an alternative BUT the latter is not a very 'accurate' choice so use with care. I have tried all three options in previous flights.
 
Do you have any specific reason to reset the homepoint?
One potential negative is inadvertently resetting to a bad location for an RTH autolanding.
But if you aren't moving far from the launch point and your launch point is out in the open, there's really no need at all to be resetting your home point.

What's sufficient?
You don't know because there's no single magic number that's "sufficient".
Don't assume anything, wait for the flight controller to determine that the GPS location data is good and record the home point for you.

Hi, it was just a general question really, as it's something that I've not done. I sometimes fly while walking, so I could be some way from my original home point

"Sufficient" for me means, wait until the Sat indicator is no longer red on the App, I no longer have the "take off with caution" message and the LED on the Mini is green

The last time I used a DJI with GPS was on a F450 "Flamewheel" with a Naza M V2 GPS, probably 7+ years ago. The procedure was always to wait for the Green light, I don't think that there was an option to reset the homepoint. It's a habit I still use today
 
You do, there are 2 symbols in the options, 1 is for the Drone the other is for the controller. You can also set "somewhere on the map" as an alternative BUT the latter is not a very 'accurate' choice so use with care. I have tried all three options in previous flights.
Oh, wow, I haven't noticed that. I'll definitely check that out next time I'm flying.
Thanks, PhiliusFoggg!
 
Well ... for the first alternative I think I rather would go for Return to controller, most mobile devices today have GPS builtin so that should work, & then periodically reset it if constantly moving (as reset to controller is to present position & not follow controller). The main purpose is to get the AC within control distance, not let it land on uncharted ground... take control & fly it all the way to you & land manually.

The second purpose is actually a bit of a clever idea ... usually during a blow away it's the AC-RC disconnect that finally makes the AC disappear to be never seen again. Usually the connection is lost no matter if the pilot tries to lose height, tries to actually land on the spot or hope that the RTH will fix it back home up wind. In all cases the connection is most probably lost & the AC execute the failsafe action, rises up & continue to be blown away until the battery is depleted & low battery force landing happens at some unknown position. But if resetting the HP a good distance down wind the AC will commence RTH with the wind & the chances that it actually will land in a relative known position is high ... then you can go there & pick it up.
I am curious about "return to controller". Suppose I set that while the drone is flying, then I walk some distance away. Will rth then send the drone to where I am now or to where I was when I set it?
 
I am curious about "return to controller". Suppose I set that while the drone is flying, then I walk some distance away. Will rth then send the drone to where I am now or to where I was when I set it?
It's not following the controller, when this function is used it logs the present position of your controller (or actually your mobile device which provides the GPS coordinate) ... if you're moving you need to redo it periodically.
 
It's not following the controller, when this function is used it logs the present position of your controller (or actually your mobile device which provides the GPS coordinate) ... if you're moving you need to redo it periodically.
Thought so. It would be nice to have both options, "current rc location" and "follow rc"
Imagine misunderstanding this while flying from a boat.
 
Thought so. It would be nice to have both options, "current rc location" and "follow rc"
Imagine misunderstanding this while flying from a boat.
Not mentioned is in order to return to controller your device must be GPS equipped, while most are, one caveat is Apple tablets such as the mini's. IF you opted to go with WIFI only (No 4G) those don't have a GPS System. Only Apple tablets that are WIFI and 4GLTE have a GPS System, but all their phones do and most Android tablets.

IF you see both Icons in App, your device is GPS equipped. :)
 
This is a great question. I thought I knew most answers to these type of questions because mainly I've got over 2000 flight hours logged in and I've been through practically every type of situation myself but where I live and fly is all flatland so I've never had to deal with different heights of terrain other than a few foot in the distance of any flight so that was something I didn't have an answer for but am glad you asked because I was able to read the responses and find out the answer. Altho the answer is what I would have guessed it to be knowing how the system works in other ways I was reluctant to give my opinion because I don't want to guess at any question asked and give the wrong info. Theres plenty of that going on in the Facebook groups and nothing makes me angrier than someone giving a wrong answer to someone else's question and I'll blast that person everytime. With that being said... new pilots to groups and forums should never except any 1 answer no matter how confident that person sounds. Some throw out a guess and don't let be known it was a guess or an assumption of how he may have taken the question. Not like you can hold that person responsible or accountable for giving a wrong answer. These kids and idiots in some of these groups don't care whether or not you crash or not. Most will see a post about someone's crash and all you ever see of the is when they are laughing at that post in the reaction comments. I see nothing funny about a crash. Even if that person has insurance and didn't cost him much it still isn't funny when you consider why that person crashed. Usually means that person did something because they weren't aware that the aircraft would react as it did and if they werent aware then that crash could have been much worse in a different scenario and someone or some kid could have got hurt. Could you imagine what could happen if a family with kids was driving a car at 60 mph and all of a sudden out of nowhere a drone came crashing into the windshield? Even if it didn't penetrate the glass it would definitely shatter it causing the driver not to be able to see in front of him. Not to mention if it was someone that would be so startled they swerved into an oncoming lane and had a head on collision with a vehicle. And this is why I will blast these idiots...END RANT
 
If I set a new Home Point during flight - does the MM know the altitude of that home-point? If not, I can see scenarios where it flies into trees, mountain walls or obstacles during a RTH-process, due to the fact that it is missing data for the altitude of the new Home Point. Am i right?
What sort of scenarios are you worried about?

If you set your RTH height to 40m, for instance, that's always referenced back to the height of your original power up and takeoff location. As others have pointed out, that recorded zero height remains the same even if you subsequently record a new home point while flying.

It's important to always survey your surroundings to take note of the highest possible obstacle you might encounter along your flight path, and set your RTH height to something safely exceeding the height of that tallest obstacle.

But it's also important to remember that, if the Mini is already flying at a height greater than your configured RTH height, when RTH is triggered it will return at that current height. It will not first descend to the configured RTH height.

So if you are planning to fly around behind a tall tree or other obstacle, make sure you are either already flying at a height greater than the top of that tree, or be certain you have configured your RTH height higher than that tree. Then, if control signal is lost the Mini will either turn for home already at its current safe height, or it will first climb to its set RTH height before heading home.

My original DJI Phantom-1 actually did record a new height whenever a new Home Point was recorded while in flight. This way you could trick it into exceeding its max ceiling limit. I made a video demonstrating this back in 2014.

With a RTH height set to 20m, the Phantom would ascend to 20m before turning for Home. That's all normal. Then I recorded a new Home Point while hovering 10m off the ground. Triggering RTH would then again cause it to climb another 20m above that recorded Home Point before heading home. In this case it climbed to 30m above ground level.

At the time, the question was what happens when it then tries to "land" at its new Home Point that's 10m above the ground? Would the motors turn off 10m above ground, or would it continue to descend until landing normally on the ground? That's why I made this video.

DJI changed this in later products. So now the Mini has a hard-coded maximum ceiling of 500m. You cannot fly higher than 500m above the recorded takeoff height. Upon reaching that limit, you cannot simply record a new Home Point while hovering at that height to reset to zero and then climb an additional 500m.

 
@ErikBad the RTH height is based on where it took of from ,so if you landed and then flew up from another home point then the RTH height would be based on the new take off point
if you just changed the home point in the app,while you were flying then the drone would still do its RTH at the height you set at the first take off point it only knows its height relevant to where it took off from it has no idea how high it is relative to the ground beneath it as it flies over changing elevations ,when it is at 30ft or less then the downwards sensors come into action and then the drones altitude is pretty accurate relative to the ground below it
Ok after thinking about it im either learning something today or everyone is lol. I didnt know the recorded RTH position took in consideration of ground level. I mean I know it has to know the the ground level in order to climb to the height you have it set at but I guess I assumed that was 2 seperate things. I assumed that GPS locations was just longitude and and latitude. Ive never heard of GPS being a 3 position thing. I thought it just added in your start off ground level to the GPS coordinates. Because if that were the case that its a 3 part coordinate then why wouldn't it tell you the 3rd part of ground level when you use "find my drone" it only gives you lat and long. I had my drone stuck in a tree once and it doesnt say whether its on the ground or 50 ft in the air off from home point. Because that would come in handy if find my drone did do that. You'd know if you should be looking on the ground or up in a tree and I feel if GPS had that ability it should certainly let you utilize wouldnt you think? Why would purposesly leave that out of the equation. I just assumed it used the the ground level at first to rise to the altitude you set it at then changed over to GPS location to get it above HP and then just started to decend until the sensors picked up ground level no matter how far it was or close it was. That would also explain why it doesnt take into consideration of height when determining if you're far enough from HP to activate RTH. What is it 30 meters away from home point correct? If it took in consideration of your ground point height then If you were 31 meters up youre technically more than 30 meters away from HP. Im thinking it only knows ground point to go to preset altitude for RTH only using how far the it has calculated your upward rise from zero when you started the flight. Which would also explain why you can reset HP at anytime during your flight and it doesn't need to calculate ground level. When you reset HP during flight you arent giving it a height just long and lat. You move the image 2d not 3d. Am I right here or have I had to much to drink tonight lol
 
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