When wanting to conduct a drone flight or mapping mission over a precise area of interest, one needs to plan the flight and path beforehand. This ensures that the entire area is covered completely and removes any visual errors or barriers that might occur during field work. Further, prefixing flight settings allows for more consistent data collection as compared to manual flights on the go.
We use a combination of two softwares for planning flights.The first among them is FlyLitchi Mission Hub (FMH) and the second is QGIS. The two can also be used in conjunction with one another. The process using both these softwares is described in this blog.
Using FlyLitchi:
FMH is a web app that enables us to plan drone flights from the desktop and later execute them using the android based Litchi app - Litchi for DJI drones which is available for a one time purchase in Google Play Store.
The FlyLitchi mission hub interface has many flights that are publicly available for viewing on the desktop app as shown in Fig 1. We can also share our flight paths and drone videos to this application.
Fig. 01: FlyLitchi mission hub interface.
Login and Register:
FMH is a free desktop application. One needs to register in order to create, upload and save the flight missions. To do this, click the ‘Log in’ button on the top right of the interface and create your account.
Set your area of interest:
a. Search for your Area Of Interest (AOI) in the search bar which is at the top left of the interface.
b. Click around the AOI to create way points to set the route of the mission.
Fig. 02: Way Point settings
c. Click around the AOI to create way points to set the route of the mission.
d. This mission can be stored by clicking on the MISSIONS option - bottom left and then clicking Save.
Way Point Settings:
I. Lat-Long: The location of the point is automatically logged as soon as you create a point.
II. Altitude (m): One needs to set the altitude of the drone above ground for all the points. In India, the legal limit as per the Directorate General of Civil Aviation (DGCA) is 120m.
There is an ‘Above Current’ option under ‘Altitude settings’ available when you are batch editing the way point attributes. The “Above Current” option in FMH allows you to add a specific altitude to the current altitude of selected waypoints. It’s a convenient way to elevate all waypoints by a set distance without adjusting each one separately.
III. Speed (m/s): One can set the speed depending on the purpose of the mission. Max speed is 15m/s.
In a video mission like this, the speed can be set between 10m/s to 15m/s.
Pro tip: If you’re designing a mission to create an orthomosaic, keep the maximum speed below 8m/s to avoid distortion.
IV. Curve (m): If the curve is 0m then the drone will exactly fly to each point and then head to the next. If the purpose of the mission does not necessitate going to the exact location (esp. Turning Points) of the points, the drone will follow a curved path (blue line in Fig: 2) near the point (curve > 0m).
Fig. 03: Curve at the turns
V. Heading: This is a circular (turn right - turn left) movement of the drone at a point location. It ranges from 0 to 360°. This controls which direction the drone is pointing. It is marked by a triangle-like marker on each way point.
VI. POI: One can set one or multiple Points of Interest (POI) in FMH. The drone automatically points to the POI if set to do so. Here you can select which POI the drone should focus on if there are multiple POIs.
VII. Gimbal Pitch: This is like the angle defining the up-down movement of the camera. One can choose between 30 to -90°, where -90° points straight down.
If you have chosen to Focus on a POI, then the drone automatically recalibrates its gimbal pitch to capture the POI throughout its mission. Alternatively, by picking the ‘Interpolate’ option, you can set a constant pitch angle which will be consistently maintained through the mission.
VIII. Intervals and actions: One can add some actions at each waypoint like Start/ Stop recording, Click a picture, Stay/ Hover etc. This option allows to set an action and the duration of the action if applicable.
Fig. 04: Way Point settings and Mission settings.
Mission settings:
I. Units: One can choose the unit of measurement here.
II. Map Type: One can choose the base map upon which the flight missions appear.
III. Heading Mode: The direction that the drone faces is set by this.
A. Auto: The drone faces the next way point.
B. Initial: The heading of the first way point is fixed for all.
C. Manual: Heading can be fixed during the flight.
D. Custom: You can set the heading for each way point in FlyLitchi.
IV. Finish Action: At the end of the automated flight, the drone follows this action.
A. RTH: Return to home - flies back to the drone launch point.
B. Land: It will land at the end of the mission.
C. Back to Start: The drone returns to the start of the mission.
D. Reverse: It comes back the same path as the mission.
V. Path Mode: The curve setting in way point settings is overridden by this path mode. If path mode is set to ‘Straight line’ then the flight path cannot have curved turns. If ‘Curved path’ is selected, one can set the curves at the points.
VI. Cruising Speed and Max Flight Speed (m/s): The speed can be set here.
VII. Default Curve Size (%): If path mode = ‘Curved turns’, then the new points that you add to the flight path will have the default curve size % that you specify. Default curve size will not work if the Path mode is set to ‘Straight Lines’.
VIII. Default Gimbal Pitch Mode: Same as way point settings but ‘MISSIONS’ settings override the way point settings.
Note: Mission settings override the way point settings.
Using QGIS to aid flight planning:
The boundary of the video mission can also be created in QGIS: This method is useful when the area of interest may not be obviously distinguishable in a satellite image. For example, if one owns a parcel of land, the boundaries need to be incorporated precisely and cannot be determined accurately through an image.
Here one has two options:
a. Load a boundary file of the AOI that you may already have.
b. Create a shapefile layer from the Layer menu.
If you already have a shapefile for your area of interest-load it into QGIS and export it as a .kml file. This is because the FMH only processes .kmls and .csvs at present. The process for importing the .kml into FMH is described towards the end of the blog.
If you don’t already have a shapefile, you can create one using the following steps:
a. Go to Layer> create Layer and select New Shapefile Layer
Fig. 05: Creating a shapefile in QGIS.
b. Choose the name, source folder and projection to save your file.
Fig. 06: Creating a line shapefile.
c. Now right click on the layer and select toggle editing. Then click on the Add line feature. You can now create a feature by digitising this boundary.
Fig. 07: Digitising a line shapefile.
d. Export this line file to a .kml file.
e. Import the .kml file to FMH using the ‘import’ option from the MISSIONS tab on the bottom left of the screen.
Fig. 08: Import kml to FMH
f. Check and edit settings of each way point as mentioned in the previous section.
Thus FlyLitchi and QGIS can be used to create video missions. The planned flights saved in FMH can then be executed using Litchi for DJI drones android app. The videos from the drone are recorded as .mp4 files.
The next step in our workflow would be processing these videos to sync them with telemetry data. More information on this process can be found on our blog on using Dashware.