What is Drone Flight Planning?

Drone flight planning is the task of choosing the route, height, speed and camera settings of a drone mission before the flight.

What a plan sets

A plan for mapping or inspection sets four things: the flight pattern, the flight height, the overlap between images and the camera settings.

The flight height sets the ground sampling distance (GSD). GSD is the distance between two consecutive pixel centres measured on the ground. It also depends on the image width, the sensor width and the focal length. GSD is proportional to the flight height, so a flight at twice the height gives twice the GSD.

For the general case, Pix4D takes the images in a regular grid. It recommends at least 75 percent frontal overlap, along the flight direction. It also recommends at least 60 percent side overlap, between flight lines. For dense vegetation, it recommends at least 85 percent in both directions. A 3D model of an urban area needs a double grid, so that the building facades are visible. For a tall structure, Pix4D recommends flying close and turning around it several times at several heights.

These figures come from the documentation of one photogrammetry product. They are not an airfield inspection rule.

Flight limits that a plan must respect

In the US, 14 CFR 107.51 sets these limits for a small unmanned aircraft:

• Groundspeed: at most 87 knots (100 mph).
• Altitude: at most 400 feet above ground level. A flight within a 400-foot radius of a structure may go up to 400 feet above its uppermost limit.
• Visibility: at least 3 statute miles.
• Distance from cloud: 500 feet below and 2,000 feet horizontally.

Under 14 CFR 107.41, a flight in Class B, C or D airspace needs prior air traffic control authorisation. The same applies in the surface area of Class E airspace designated for an airport.

In the EASA area, the open category requires a flight altitude below 120 m above ground level. The specific category applies outside the open category limits, for example above 120 m. It has four ways to operate: a standard scenario declaration, a PDRA, a SORA, or a light UAS operator certificate. The authority of the state of registration issues the authorisation.

Each EASA Member State also sets drone geographical zones. Zones near airports can bar drones or require a flight authorisation. They cover all drone categories. Ask the national aviation authority for the local zones before you plan a flight.