Launch Type: Waypoints vs. Virtual Sticks

Drone Harmony Mobile offers two fundamentally different ways of launching the drone in a Drone Harmony automated mission: Waypoint and Virtual Stick. In this article we describe the differences between them and gives a few recommendations with regard to which launch type is advised in which situation.

What is a Launch Type?

A launch type determines the way that Drone Harmony Mobile and the DJI firmware combine to control the DJI drone in an automated mission. There are two launch types: Waypoints and Virtual Stick.

Most missions can be safely flown with any launch type. There are, however, several factors that would favor using one type over another, or even enforce using a certain launch type:

• The used drone model: certain drone models are only enabled by DJI in the virtual stick mode,
• The capture mode: certain capture modes are only enabled by DJI in the virtual stick mode,
• Whether the mission includes a certain type of waypoints, such as Panorama waypoints,
• Advanced aspects related to desired in-flight behavior and the physical environment.

What happens in the background in every launch type?

There is a fundamental difference in the way that Drone Harmony handles flight execution in each launch type. While it is only important to understand the behavior of each, it can also be instructive to understand what happens behind the curtains.

Before we speak of the differences, let’s state the commonalities: when you execute a mission in Drone Harmony, regardless of which launch type or capture mode you are using, you start with a waypoint mission, composed of Drone Harmony waypoints. These waypoint encode the desired flight trajectory and the camera actions. When launching you also choose additional parameters, such as flight speed and various actions, such as end-of-mission action.

When launching the mission in the waypoint launch mode, Drone Harmony translates the Drone Harmony waypoints into DJI’s representation of waypoints and uploads the result to the drone. The DJI firmware is then responsible for the physical execution of the mission, namely for following properly the flight path and triggering the camera. Drone Harmony remains in the background monitoring the flight execution.

When launching the mission in virtual stick launch type, Drone Harmony Mobile translates the Drone Harmony waypoint mission directly into RC stick commands (hence the name “virtual stick”). These RC stick commands are sent many times per second to the drone through the RC radio connection. Intuitively, Drone Harmony Mobile is simply emulating in software a human pilot that would try to follow the pre-planned waypoint mission by using the stick commands. As a result, this flight mode requires continuous stable radio connection between the RC and the drone.

What is the difference between Launch Type and Capture Mode?

A launch type determines how the drone is controlled by Drone Harmony on a low level – what control algorithm is used to move the drone and its payload during flight.

The capture mode, on the other hand, determines higher-level attributes of the mission: what data should be captured (photo/video/nothing), whether the drone should stop at every waypoint etc. While most capture modes are enabled in both waypoint and virtual stick launch types, some capture modes require the use of a specific launch type (see below).

I have a Drone Harmony waypoint mission. Do I have to execute it in Waypoint launch type?

No. Every mission in Drone Harmony is a waypoint mission. The launch type determines how the mission will be flown, no whether it is a waypoint mission or not.

There are, however, kinds of waypoint missions that require the use of a specific launch type (see below). In such cases, the launch dialogue in Drone Harmony Mobile will automatically restrict the choice of launch types to that specific mode.

What are the advantages of each launch type?

Each launch type has both advantages and disadvantages. While in some cases the attributes of the mission, or drone, determine the required launch type, in many cases both options are available. It is hence useful to know what properties they have in order to minimize risks and maximize performance in the automated flight. The following are the main advantages of each launch type.

Waypoints

• Better performance on a wider range of devices: since the DJI firmware is responsible for all low-level drone maneuvers, the drone flight control algorithm places a lesser computational burden on the mobile device.
• Flights outside of radio signal range are possible: while it is not advised to fly outside of radio signal range, it can happen that radio signal gets lost during an automated flight. This can happen in long flights as well as flights in an environment with many large obstructions. The waypoints launch type enables you to choose a launch dialogue parameter that instructs the drone to continue flight along the the pre-planned route in such a situation.
• generally smoother flights for video captures: in some cases, waypoint execution mode leads to a more cinematic feel to a video capture.

Virtual Stick

• More flexible and dynamic capture modes and waypoint actions: virtual stick launch type enables a number of capture modes and more complex types of waypoints (such as panorama waypoints).
• No waypoint uploads: there are no upload sequences when executing with virtual stick launch type. In particular, the drone takes off immediately upon launch and long missions are executed uninterrupted without uploads in batches (that are needed in waypoint launch type due to DJI’s waypoint upload limits).

The main advantages and disadvantages of each launch type are listed in the launch dialogue in Drone Harmony Mobile on the appropriate screen, so there is no need to memorize them.

In what scenarios is the launch type determined by other parameters of the mission?

As we mentioned before, certain features of Drone Harmony missions are only enabled in certain launch types. Here is a (potentially non-exhastive) list of such scenarios.

Mission parameters that are only enabled in virtual stick launch type

• You are using one of the following drones: Mini, Mini 2, Air 2S, Spark.
• You have panorama waypoints in your mission.
• You are using the auto-fly & manual shoot capture mode.

Mission parameters that are only enabled in waypoint launch type:

• You plan to fly a mission that requires flight outside of radio signal range (e.g. in case of flying around very large obstructions).

Important Safety Considerations

Drone Harmony works hard to ensure the safety of flight execution in any launch type. It is, however, important to keep the following information in mind.

In case you are using the virtual stick launch type:

• You should always strive to have good radio signal strength.
• In case of signal loss, the drone will hover in place. You will have to relocate to regain the signal. In case you are unable to relocate appropriately, the drone will initiate a fail safe procedure and land when the battery level drops below a threshold.
• Be prepared to see the drone take off immediately upon launch, as there is no upload sequence.
• By touching the control sticks you immediately pause the automated flight and regain manual control (the drone will hover). You can choose to resume the mission by tapping on the appropriate button in the app.

In case you are using the waypoints launch type:

• If you are flying a long mission (with more than 99 waypoints), be prepared for batch-uploads, namely situations in which the drone stops in the air and another waypoint upload sequence begins. This will happen every 99 waypoints for all drones different from the Matrice 300. This is required in waypoint launch type due to a DJI restriction on the largest possible waypoint upload batch. For the M300, this restriction does not exist, and hence no batch uploads should occur.