NEW PILOT RTH Question

THook · Mar 22, 2018

OK.. Lets say you have RTH set to 150'. Is that AGL no matter where the drone is? In other words.... The drone is coming home straight line and comes into terrain that is higher than the route you just flew over... Will it auto adjust to the terrain at the set 150'?? Thanks ....I'm sure I'll have a bunch of stupid questions.....

msinger · Mar 22, 2018

When RTH is iniated, the Mavic will ascend from the current altitude displayed in DJI GO up to the RTH altitude. If the Mavic is already above the RTH altitude, it'll return to the home point at its current altitude.

The Mavic does not know where the ground is located below it, so you should always make sure you set an appropriate RTH altitude before taking off.

Mossiback · Mar 22, 2018

THook said:
OK.. Lets say you have RTH set to 150'. Is that AGL no matter where the drone is?.....

The 150' is relative to the takoff point. After a certain height, the Mavic does not know where the ground is, just it's current position relative to the take-off point. If you take off from a hilltop and go down, your height reading will display negative numbers.

THook said:
... Will it auto adjust to the terrain at the set 150'??....

Once it is returning to home, the only adjustments to terrain it will make is if an obstacle is detected. It will either raise up or move to the side until the obstacle is no longer detected, or hover depending on the settings. The preferred setting is to raise up.

THook · Mar 22, 2018

Mossiback said:
The 150' is relative to the takoff point. After a certain height, the Mavic does not know where the ground is, just it's current position relative to the take-off point. If you take off from a hilltop and go down, your height reading will display negative numbers.

Once it is returning to home, the only adjustments to terrain it will make is if an obstacle is detected. It will either raise up or move to the side until the obstacle is no longer detected, or hover depending on the settings. The preferred setting is to raise up.

OK what I thought... THANKS!

chazzm · Mar 23, 2018

Mossiback said:
The 150' is relative to the takoff point. After a certain height, the Mavic does not know where the ground is, just it's current position relative to the take-off point. If you take off from a hilltop and go down, your height reading will display negative numbers.

Once it is returning to home, the only adjustments to terrain it will make is if an obstacle is detected. It will either raise up or move to the side until the obstacle is no longer detected, or hover depending on the settings. The preferred setting is to raise up.

I’m not going to say it’s wrong because I know that the most preferable setting is to rise up, I’m just throwing in my thoughts after doing a little research in Drone crashes I found that a surprising number were caused by raising up instead of going around! Tree branches, awnings, all due to no top sensors. Moving to the side logically makes more sense because of having forward sensors. And I’m not going to beat a dead horse (because that suckers mummified by now! LoL) but these beautiful wonderful drones have 4.7 km range or whatever model your flying, it’s ludicrous to think an operator is going to maintain LOS with the AC when you have the flight time and range we have now! On a side note 94% Operator error to include incorrect settings in RTH and/or manually turning the sensors off. And a number were due to other “Raptors” LoL

Simmo · Mar 23, 2018

Most of those things like trees branches and awnings are not 100 feet in the air.
The crashes you are on about that are so common with new operators is a RTH triggered when fairly low and even close by, where the RTH height has been set too high for the location. Hence hitting awnings etc. 100% operator error.
The true use of RTH comes in when 'issues' arise, when you are out flying proper..... you want your AC to rise above surrounding terrain to come home.

aksobby · Mar 23, 2018

Remember Line Of Sight and have no worries.

THook · Mar 23, 2018

Yeah the reason I was asking is I had my RTH set to 150' on flat terrain where I lifted off... flew across a field and followed a stream for a while... when I hit low bat warning I hit RTH which put the drone in a direct flight to my return point... there was a small hill that was maybe 60' higher than my take off point on its return route and it appeared it was getting too close to the tree tops so I just gave it some altitude... I didn't know if the sensors would save me and I didn't want to find out... good thing I was vigilant.

NestleQuik · Mar 24, 2018

Just curious, if a hill was 60 feet higher on the way back, didnt you encounter that hill on the way there? I wrote this on another thread, you can use google earth to view your location before flying, scroll over points in the direction you intend to fly and check what the change of elevation is where ever the cursor is. if your elevation is a 100ft where you are taking off and you are moving it the direction you plan to fly at 150ft and the number gets lower say like 60ft it means the ground is higher and when you fly over it, you are going to be 110ft ft AGL in that area, if the number gets higher 200, it mean the ground is lower at that point, and you will be 350ft AGL Do a lil math and you can set your setting accordingly.

you RTH height is from the Home Point from which you take off, what ever that elevation will be. But i do the google elevation check, if i think i may be flying in another unfamiliar area, you can observe the elevatioon change in the lower right corner when you have the map pulled up, just view what obsticles are in the area as well, scroll over them too. the elevation should constantly be changing.

NestleQuik · Mar 24, 2018

I had thought about this being in the US, if you are flying over an area say at 200ft, and the elevation of the area you fly over descend by lets say 300ft, that now you are in violation of the FAA rule of not flying above 400ft, technically hahaha crazy huh hahaha

Mossiback · Mar 26, 2018

chazzm said:
...I know that the most preferable setting is to rise up, I’m just throwing in my thoughts after doing a little research in Drone crashes I found that a surprising number were caused by raising up instead of going around! Tree branches, awnings, all due to no top sensors. Moving to the side logically makes more sense because of having forward sensors

It's a judgement call. The forward sensors will not detect an obstacle to the side. If you plan on flying under things (trees, awnings, etc) set RTH to hover.