Flight planning for roof measurements

How do I fly a roof survey with the DJI Mavic 3E? (also applies to other DJI Enterprise drones)

Video tutorial for the DJI Mavic 3E

Best Practices

Fly parallel to the course of the house! How to reduce errors due to lack of overlap.

Example of a commercial building:

Example single-family house:

How do I fly a roof survey with the DJI Mini 3 Pro / Mini 4 Pro? (also applies to other DJI drones such as Air, Air 2s, Mavic 2 and similar)

Video tutorial for the DJI Mini 3 Pro with DJI RC

Click on the video to start the video embedding by Youtube.

Quasi-square buildings (e.g. detached or terraced houses)

• Fly manually at approx. 5-10 m above ridge height

• Position the drone away from the building, not directly above the roof. See figure 1.

• Flight altitude: The lower is better, but not too close! You should pay attention to the obstacles around the house and along the flight path of the drone.
  
  In addition, photos should contain distinguishable patterns for good alignment of the photos (i.e. they should not contain only +70% of the roof objects in individual photos, for example. This can lead to empty roofs on the model. So you should not be so close to roofs in photos. It is all the better to see roofs, surfaces or other patterns together on photos! ) See figure 2.

Figure 1: Circular trajectory

• Manually adjust the gimbal tilt between -45° and -60° (the camera's field of view must cover both the roof and the facades of the building). See figure 2.

Figure 2: Field of view for flight with inclined camera (Oblique)

• Draw a point of interest (POI) in the centre of the object you want to photograph

• Select "Hyperlapse" mode and then "Circular" from the shooting modes

• Set "2s interval" for time interval shots (see Figure 3)

• 75-100 photos are sufficient for a single house. Select "3-4 s hyperlapse length" for this (see Figure 3)
  
  Tip: You can select a longer length (e.g. 8 s) for larger projects than for a single house. This means that you will receive more images per round trip.

• Select an airspeed of 1-2 m/s. (1 m/s is preferable for a detached house, see Figure 3)

• Don't forget to select "JPEG" as the format type! (See figure 4)

• Then select the red record button on the right and start the flight! (See figure 3 or 4)

Figure 3: Hyperlapse settings

Figure 4: Hyperlapse recording format

Tip:

Make sure to cover the entire parts of the building that you want to obtain as a 3D model with the photos. Otherwise, part of the building (e.g. garage or roof) may not be included in the model. We process your data by taking into account the location of your photo and its angle of view and receive an export according to your focal points on the photos.

Rectangular buildings and large buildings e.g. apartment blocks or industrial buildings

For larger buildings, circular flights are usually not suitable. However, in this category we have several options for multiple drones:

• Depending on the characteristics of your drone, you can use the "Oblique", "Smart Oblique" or "3D Photogrammetry (Double Grid)" modes for flight planning. All give almost identical results.
• Draw your flight area (= polygon area)
• Set the appropriate height by taking into account that the roof photos are not taken so close (i.e. not only +70% of the roof objects should be included in individual photos, for example. This can lead to empty roofs on the model. So you should not be so close to roofs in photos. It is all the better to see roofs, faces or other patterns together in photos)
• Select the angle of inclination of the gimbal between 45°-60° (compare: 90° would be vertically downwards, i.e. we want to look at the roof surface at an angle)
• Set the lateral overlap to 70 % and the longitudinal overlap to 80 %

Quality check

• Open images
• [If reconstruction of facades desired: Facades visible?
• All details of the roof clearly recognisable?
• Roof photos are not taken too close?
• Do photos look high quality? (e.g. they should not be blurred)
• Do the photos cover and focus on all objects that need to be included in the 3D model?
• Does my "Hyperlapse" output in "JPEG" format? (It should not be a hyperlapse video!)

FAQ

How can individual objects be depicted well?

Small objects (lightning rods, lanterns, satellite dishes, etc.) are often not modelled optimally, or are not even visible in the 3D model. The reason for this is that information about these objects can only be found in a few images. If you want these objects to be well modelled, simply fly around the object again one by one. This provides more photos and therefore more information that can be processed.

How can I display facades correctly?

The more tilted the camera is, the better the facades will be visible. But beware: don't forget that the quality of the roof is unfortunately affected!