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RTH and the Return at Current Altitude option mystery

mha1

Active Member
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Aug 1, 2018
Messages
26
Age
41
Hey Spark pilots,

I tried to get a grip on my Spark’s RTH behavior and found mostly misleading tutorials especially on how the DJI GO 4 app “RTH at Current Altitude” option influences the RTH process. After reading the relevant section of the manual over and over again with drawing flow charts let me try to shed some light on the Current Altitude option mystery.

Just a quick recap of how RTH is engaged. For RTH to work it is necessary to have a valid home point recorded and good GPS lock at the instance RTH is triggered. RTH is triggered either manually (smart RTH) by tapping the RTH icon in the DJI GO 4 app or pressing and holding the RTH button on the remote controller or it is triggered automatically by a low battery or loss of signal.

Two settings in DJI GO 4 app are relevant for how RTH behaves after being triggered

- Setting #1: The “Return-To-Home Altitude” setting, i.e. pre-set RTH altitude
- Setting #2: The “RTH at Current Altitude” option

Once the RTH is triggered there are four cases dependant on the drone's distance to the recorded home point to consider.

Case #1 - The drone's distance to the recorded home point is less than 3m
In this case the drone will descend to land immediately from its current altitude and position.
Note: The Current Altitude option is ignored in this case. The drone will not ascend to the pre-set altitude even if the Current Altitude option is disabled.

Case #2 - The drone's distance to the recorded home point is between 3m and 20m with the Current Altitude option disabled.
The drone will immediately descend to land from its current altitude and position.

Case #3 - The drone's distance to the recorded home point is between 3m and 20m with the Current Altitude option enabled
The drone will check its altitude. If its current altitude is above 2.5m the drone will RTH at its current altitude immediately. If the altitude is less than 2.5m it will ascend to 2.5m first and then start to RTH.

Case #4 - The drone's distance to the recorded home point is greater than 20m
The drone will check its current altitude. If the drone is higher than the pre-set altitude it will start to RTH at the current altitude immediately. If it is lower than the pre-set altitude it will ascend to the pre-set altitude first before starting to RTH.
Note: The Current Altitude option is ignored in this case. The drone will always return at the pre-set altitude at a minimum.

Conclusion: The Current Altitude option setting is only taken in account in a scenario where the drone's distance to the recorded home point is in the 3m to 20m bracket. In all other cases the Current Altitude option setting is disregarded. It is perfectly safe to enable the Current Altitude option to avoid immediate landing in case of an RTH event in the 3m to 20m range. If the drone is further out it always returns at the pre-set altitude at a minimum.

Hope this helps.

Michael


Source: Spark User Manuel V1.6
 
Last edited:

OB TV

Member
Join
Nov 5, 2018
Messages
7
Age
56
It's amazing what can be learned when people actually read the instructions!
That is one of my favorite things about getting a new product. You never know the full capability of a product unless you read. While others would rather muck it up and have someone else solve their problems. DJI products are complicated pieces of machinery and need to be treated as such. I encourage everyone to fully read the manual because shortcuts lead to accidents and incidents. Reading all the forums in the world will never give you as much insite as the instructions will. Also more accidents and incidents will only lead to increased regulations. Look at what is happening in the UK right now. The commercial drone industry is already gunning for our airspace. Let's not give them the ammunition they need to take away the hobbyist and 107 pilots right to flight!
 

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