I'll read your compass calibration post after this and may find the answer to my question. How do read the compass to see if it needs to be calibrated?
Lost mine today, RTH failed.
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I'll read your compass calibration post after this and may find the answer to my question. How do read the compass to see if it needs to be calibrated?
JKDSensei, thank you for asserting that I don't know what I'm doing, same goes for the moderator. No, I did not get it for Christmas and fly it right out of the box. I "brushed up" my knowledge quite a bit as I have been flying this thing for months quite successfully. Prior to ever flying it I watched every DJI video repeatedly, spent hours on the flight simulator, and have been enhancing my knowledge by reading this forum. I had come to fully trust RTH to bring it back to the area but don't allow it to auto-land per the drift of up to 12 feet in the landing point I mentioned in an earlier post.
Prior to this flight I was prompted to calibrate the compass. I was atop a parking structure so I suspected rebar in the concrete might have been a problem, on the third attempt it was successful, the error cleared and allowed the motors to start. I previously manually changed RTH altitude to 90 meters (high enough to clear any objects in the area), and had the green "safe to fly GPS mode" indicator on the app, steady green rear arm lights, and a verbal "return to home location set" notification.
During this flight RTH engaged once and worked fine. Once it was nearby I cancelled RTH and continued to fly. The second time RTH engaged I was near a tall building. It is very possible that the antenna array atop that building could have caused signal interference. So, if that is the case, is fly off a likely outcome, and could interference be the cause for the RTH fail?
Prior to this flight I was prompted to calibrate the compass. I was atop a parking structure so I suspected rebar in the concrete might have been a problem, on the third attempt it was successful, the error cleared and allowed the motors to start. I previously manually changed RTH altitude to 90 meters (high enough to clear any objects in the area), and had the green "safe to fly GPS mode" indicator on the app, steady green rear arm lights, and a verbal "return to home location set" notification.
During this flight RTH engaged once and worked fine. Once it was nearby I cancelled RTH and continued to fly. The second time RTH engaged I was near a tall building. It is very possible that the antenna array atop that building could have caused signal interference. So, if that is the case, is fly off a likely outcome, and could interference be the cause for the RTH fail?
Meta4
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This almost certainly is the cause of your problem.
You got a compass error because your compass detected an abnormal reading - caused by the proximity of a whole lot of steel in the concrete structure.
You then recalibrated your compass to compensate for a strong magnetic influence.
When you flew away from that distorted magnetic field, your compass is now in trouble because it's compensating for something that isn't there.
Unnecessary recalibration of a perfectly functioning compass has the risk of doing this - getting a bad calibration in a bad location.
There was probably no interference but if there was, it would most likely only swamp your controller signal, leaving the Phantom to RTH because of a lost signal.
Interference never causes a Phantom to fly away.
A bad compass calibration will cause a Phantom to have trouble flying to where it wants to.
This is an educated guess based on the little information presented.
Flight logs will give more info to go by.
But your comment regarding compass calibration indicates this is almost certainly the cause.
I'm not arguing the point, seems like the calibration would be the culprit to me too, but why would the RTH work the first time, and during the same flight not work the second time? That seems odd.
Meta4
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I don't know ... we know very little about the flight or the location.
We don't know how far away both RTH attempts were initiated or what obstacles may have been nearby.
Perhaps the first RTH was from a different direction and the compass compensation wasn't significant but if the second was from somewhere else, it could have been a different situation altogether.
But what is known is that the OP calibrated his compass within a distorted magnetic field - and had to try three times to get the compass to compensate for it.
That says it all.
The compass was screwed up and the Phantom would have trouble flying straight with a compass that isn't working properly.
Maybe the the Phantom switched to atti because it couldn't resolve the conflict between the compass and GPS data. That would have allowed it to drift and it's probably autolanded somewhere when the battery ran low.
There are lots of maybe scenarios.
I'd like to see the flight logs to fill in the blanks.
They may even point to a likely location to search.
ianwood
Taco Wrangler
A bad compass calibration can cause RTH to fail. Calibrating on a parking structure is really really bad. As is any man made environment. Only do it in known safe places.
You are far better off with a good calibration from somewhere not too far away vs. a bad one from your take off point.
You are far better off with a good calibration from somewhere not too far away vs. a bad one from your take off point.
I just remembered, smart RTH only works once per flight, that's why the second rth didn't bring it back. It may not have been a bad calibration after all.
Sorry for your loss & hope you are able to find her. I have used RTH many hundreds of times with 100% success. That isn't to say RTH isn't infallible or that something else may have occurred on the way back that caused it to not return. I doubt the antenna array had anything to do with the incident as I have flown within a couple feet of cellular arrays with no effect on the aircraft. I would more suspect the compass calibration issue you experienced at liftoff.
I assume you plotted & searched the line between you & the last recorded location? A little late now but this is why I recommend a Flytrex or another reliable tracker be included on your aircraft. At least you have a means of accurately locating your bird.
I assume you plotted & searched the line between you & the last recorded location? A little late now but this is why I recommend a Flytrex or another reliable tracker be included on your aircraft. At least you have a means of accurately locating your bird.
Sorta on the topic...why doesn't dji implement a safe fly zone and a nfz 1.7xxx?! Well, I guess that's the top 10% controlling us all! I get why they have nfzs but they should also in respects to dji's customer base they should keep things even keel. Step up the game in 2016!
Really? So if i have a rth situation then cancel it once back in range, the next time it needs rth in the same flight it wont work?
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Some users have said that the Return to Home function, is in fact a button designed to lose your drone. However, this is certainly not the case. The objective of this article is to clear up some misunderstands related to the RTH button.
What are the prerequisites of RTH?
When GPS signal strength is GREATER THAN SIX BARS and you hear the app say “Home Point Recorded.”
Please take note of your location. There will also be a green H on the map, which means the Home Point is set and the RTH function is ready to use.
Some users have had accidents after pressing the RTH button, because their drones unexpectedly ascend and crash into something. Therefore, it is essential to understand the logic of the RTH function. Let’s have a look of these pictures from the manual:
There are two ’20 meters’ mentioned in the pictures above. One of the measurements is altitude and the other is horizontal distance.
If RTH is triggered below an altitude of 20 meters, the aircraft will automatically ascend to 20meters, since that is the altitude set by default in the app. The drone can’t be controlled during ascension. This parameter can be adjusted in Flight Control Settings > Advanced Settings > RTH.The default value is 20 meters, but can be modified it according to the situation.
Once RTH is pressed, this is what the drone thinks:
“Master is commanding me to return home.” (When receiving the RTH command)
“Alright, I’m ascending to the preset RTH altitude! Nothing can stop me from ascending!’ (To the predetermined height)
‘Ok, now I’m adjusting my nose towards master.’ (Adjusts direction)
‘I’m on my way back now!’ (Returns to the Home Point)
‘I’m going to land now!’ (Descends after reaching the Home Point)
Please remember that the drone can’t be controlled while rising to the RTH altitude!
What is the 20 meters of horizontal distance?
“Aircraft automatically descends and lands if RTH is triggered when the aircraft flies within a 20 meter (65 foot) radius of the Home Point. Aircraft will stop ascending and immediately return to the Home Point if you move the throttle stick if the aircraft reaches 20 meters (65 feet) altitudes or beyond during Failsafe.”
When the drone flies within a 20 meters radius of the Home Point and the RTH button is pressed,the aircraft thinks:
‘Master is directing me back to home.’ (When receiving the RTH command)
‘I’m in within 20meters, and I can land now! I don’t need to ascend.’ (The drone descends and lands without turning the nose)
TIPS:
The drone automatically lands when RTH is triggered within a 20 meter radius, BUT users can operate the control stick to avoid dangers!
PS: If the flight altitude is higher than the RTH altitude,the drone will just turn the direction of the nose and return to the HomePoint.
PPS: If the RTH altitude is set as 50 meters and the user pushes the throttle stick, the drone will return at the current flight altitude. It’s easy to crash into something.
DO NOT operate the control stick when the drone is returning to the Home Point!
In the next section, we’ll look at some examples of crashes and flyaways while using RTH.
Example 1:
“After pressing RTH button, the drone ascended and hit an obstacle.”
Remember that the drone will ascend to the RTH altitude when RTH is triggered!
Example 2:
“When flying the drone on a mountain, I lost image transmission. When pressing the RTH button, the remote controller sounded, but I could not find my drone. So I operated the sticks, and the drone lost.”
Don’t operate the control sticks if you can’t see your drone! Just wait patiently for it to return to you. Make sure you record a Home Point before flying.
Example 3:
“When pressing RTH button, the drone automatically descended into the water.”
Remember, the drone automatically lands if RTH is triggered when the drone is within a 20 meters radius of the Home Point. Unlike in the previous case, use the control sticks to stop the drone from descending!
Please remember to set the Home Point before using RTH and wait patiently during the return. DO NOT look for the drone anywhere else.
Also, please remember to set the RTH altitude.
What are the prerequisites of RTH?
When GPS signal strength is GREATER THAN SIX BARS and you hear the app say “Home Point Recorded.”
Please take note of your location. There will also be a green H on the map, which means the Home Point is set and the RTH function is ready to use.
Some users have had accidents after pressing the RTH button, because their drones unexpectedly ascend and crash into something. Therefore, it is essential to understand the logic of the RTH function. Let’s have a look of these pictures from the manual:
There are two ’20 meters’ mentioned in the pictures above. One of the measurements is altitude and the other is horizontal distance.
If RTH is triggered below an altitude of 20 meters, the aircraft will automatically ascend to 20meters, since that is the altitude set by default in the app. The drone can’t be controlled during ascension. This parameter can be adjusted in Flight Control Settings > Advanced Settings > RTH.The default value is 20 meters, but can be modified it according to the situation.
Once RTH is pressed, this is what the drone thinks:
“Master is commanding me to return home.” (When receiving the RTH command)
“Alright, I’m ascending to the preset RTH altitude! Nothing can stop me from ascending!’ (To the predetermined height)
‘Ok, now I’m adjusting my nose towards master.’ (Adjusts direction)
‘I’m on my way back now!’ (Returns to the Home Point)
‘I’m going to land now!’ (Descends after reaching the Home Point)
Please remember that the drone can’t be controlled while rising to the RTH altitude!
What is the 20 meters of horizontal distance?
“Aircraft automatically descends and lands if RTH is triggered when the aircraft flies within a 20 meter (65 foot) radius of the Home Point. Aircraft will stop ascending and immediately return to the Home Point if you move the throttle stick if the aircraft reaches 20 meters (65 feet) altitudes or beyond during Failsafe.”
When the drone flies within a 20 meters radius of the Home Point and the RTH button is pressed,the aircraft thinks:
‘Master is directing me back to home.’ (When receiving the RTH command)
‘I’m in within 20meters, and I can land now! I don’t need to ascend.’ (The drone descends and lands without turning the nose)
TIPS:
The drone automatically lands when RTH is triggered within a 20 meter radius, BUT users can operate the control stick to avoid dangers!
PS: If the flight altitude is higher than the RTH altitude,the drone will just turn the direction of the nose and return to the HomePoint.
PPS: If the RTH altitude is set as 50 meters and the user pushes the throttle stick, the drone will return at the current flight altitude. It’s easy to crash into something.
DO NOT operate the control stick when the drone is returning to the Home Point!
In the next section, we’ll look at some examples of crashes and flyaways while using RTH.
Example 1:
“After pressing RTH button, the drone ascended and hit an obstacle.”
Remember that the drone will ascend to the RTH altitude when RTH is triggered!
Example 2:
“When flying the drone on a mountain, I lost image transmission. When pressing the RTH button, the remote controller sounded, but I could not find my drone. So I operated the sticks, and the drone lost.”
Don’t operate the control sticks if you can’t see your drone! Just wait patiently for it to return to you. Make sure you record a Home Point before flying.
Example 3:
“When pressing RTH button, the drone automatically descended into the water.”
Remember, the drone automatically lands if RTH is triggered when the drone is within a 20 meters radius of the Home Point. Unlike in the previous case, use the control sticks to stop the drone from descending!
Please remember to set the Home Point before using RTH and wait patiently during the return. DO NOT look for the drone anywhere else.
Also, please remember to set the RTH altitude.
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Meta4
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I don't think that's right. I've never seen mention of it in the manuals etc.
Each RTH instance is quite separate and there's no reason it would prevent using again
I have frequently used RTH multiple times in a single flight.
Easy enough to test this for anyone interested..
Re; Compass calibration and recalibration. Would it not be a good idea to buy a simple hand held basic magnetic compass to confirm that the N being used the a/c is in actual fact true magnetic N. Then if you move location you can just compare the onscreen compass to the hand held. Somebody mentioned issues with flying in urban areas, surely these a/c are, for many , intended to be used in urban areas? Hence the requirement for UAV CAA permissions etc; for commercial use. If the onboard compass is "likely" to be affected to such an extent by magnetic effect in those and possibly lose GPS signal as well due to large objects (buildings) maybe a connection with mobile telecommunication masts for triangulation purposes could be looked at by DJI , it may not get you back to within a metre but certainly within 20m. Just a thought from a newbie.
Meta4
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Not really. There is no compass display to compare in the app. But this isn't really the problem.
The problem is people unnecessarily recalibrating in an area with a distorted magnetic field and screwing up a perfectly good calibration.
The solution is to understand compass calibration, what it does, when to do it and where not to do it.
It was mentioned ... but urban areas present no particular compass or GPS issues for flying.
The compass isn't likely to be affected in flight - but it is if you launch from a concrete structure, manhole cover, your truck or anywhere else in close proximity to a lot of steel. And if you recalibrate your compass to deal with the magnetic distortion, you stand a good chance of having problems in the air.
When you see a Compass Error message - it's not saying that there is a problem with your compass - It's saying that your compass has detected an error.
The appropriate action is to move away from the steel that is causing the error condition.
What I mean by the compass display is incorrect, my error ,sorry, the display on the app shows the orientation of the nose of the a/c , so if you point it due N as per your hand held it should show as being the same orientation on the display, hard to explain......, I sail, if my boat is heading N on the gimbal compass I check on my Silva occasionally just to check they are the same, you'd know if the display was more than a few degrees out. Thanks for clarifying about the start up in urban areas ,near trucks ,manholes etc: I bloody love this Forum ;-)
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Why have people used RTH hundreds of times? I tried it once and never used it again. It is an emergency feature, not a button to use to simply let it come back. You should always fly back to your location under your own control.
BS. RTH is a feature, not an emergency feature. I use it multiple times PER flight. It is amazing really.
People above are confusing Smart RTH, Failsafe RTH and RTH. They all have their different logic.
I like to know how things work. I've tested RTH more than 100 times, as I said multiple times in flight. You CAN operate the controls while it is returning to home. You can control the camera pan the entire trip back. The P3 will fly towards its home point, NO MATTER its orientation. You can increase or decrease its RTH speed with the elevator stick (22 mph, +/- 7 mph). You can raise and lower its altitude above or below the set RTH height. When I see the P3 is clear of obstruction, I lower it below my set RTH altitude so I don't wait as long descending during landing.
I have never entered a Smart RTH yet, where the P3 RTH's due to battery levels, calculating what it needs to get to the home point. I have also never entered a Failsafe RTH where RC signal was lost for more than 3 seconds. I imagine they will work the same way as activating the RC or the tablet to RTH.
SD
Smart RTH is when the P3 calculates how much energy the battery needs (+ reserve) to get back to the home point. You will only get this RTH once. If you cancel, it will not reactivate a Smart RTH from the battery level for the rest of the flight.
SD
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