DJI Mavic Mini

The multicopters I have used so far are my own designs based on components from the company HiSystems (Mikrokopter.de) and have the task of transporting larger cameras for the best possible image results. Since I attach great importance to redundancy and safety, these multicopters are large and heavy, with flight times of around 10 minutes. This gave rise to the desire to build or purchase a small drone that makes it possible to quickly and easily ascend to an interesting location to check whether the ascent with a large drone is worthwhile at all.

When DJI introduced the small consumer drone "Mavic Mini" at the end of 2019, my wish for such an "always with you" drone came true. For the affordable price of 399 EUR (499 EUR for the Fly More Combo with 2 additional batteries and a propeller guard), you get a small drone that even falls below the 250g limit (if nothing is additionally attached) and thus currently requires no marking, registration or proof of capability. Nevertheless, an appropriate liability insurance policy must of course be taken out and the pilot must have the appropriate knowledge of the requirements of the German Air Traffic Licensing Regulations (LuftVZO) and the German Air Traffic Regulations (LuftVO). Furthermore, the federal state-specific conditions for an ascent permit must also be observed.

In the following I summarise my own experiences with this mini-drone especially in aerial archaeological use.

Advantages

• Size: The small dimensions of the Mavic Mini, especially when folded, are simply ingenious. You can always have it with you, it fits in any backpack and the low weight is not a problem even on long walks.
• Flight time: DJI's stated maximum flight time of 30 minutes is very optimistic, but you can definitely stay in the air for more than 20 minutes on one battery charge. This allows either longer inspection flights or multiple ascents at different locations.
• Batteries: The small batteries are quickly changed and can be charged via USB in the drone or via the charging station supplied in the Fly More Combo. This means that discharged batteries can also be recharged on the move in the car or via a power bank carried along. The same applies to the remote control. Due to the small size of the batteries, you can also carry them comfortably in your pocket so that they always have the right operating temperature, even in winter.
• Camera: The camera takes photos with a resolution of 12 MP (4000 x 3000 pixels) and is held steady in position by an extremely responsive 3-axis gimbal. The camera can be tilted downwards by up to 90°, so vertical shots are no problem. Thanks to the wide angle known from action cameras (equivalent to about 24mm) and a field of view of 83°, even larger objects (complete square enclosures or villae rusticae) can be captured on a vertical photo. I was amazed at the good correction of the wide-angle distortions.



• Propeller protection: A lightweight plastic cage to protect the propellers is available as an accessory. This prevents damage to the propellers and a crash of the drone in case of wall contact (e.g. when flying inside rooms) or unintentional contact with obstacles. I use this propeller protection e.g. when flying over ground monuments located in the forest. It hardly increases the total weight of the drone, but causes the drone to weigh more than 250g and must now have a fireproof badge.

Disadvantages

• Size: The small size of the Mavic Mini also has disadvantages. It is barely visible to the naked eye even at a distance of 100m, making it very difficult to see the drone's orientation in the sky. To make matters worse, it is a light grey colour, which makes it difficult to distinguish from the sky.
• Weight: The low weight makes the Mavic Mini particularly susceptible to wind. It reacts very quickly to changes in position caused by the wind and keeps its position very stable. However, in stronger breezes, the built-in safety function alerts you to land.
• Radio transmission: DJI uses a modified Wi-Fi signal for the control and live image transmission of this drone. This can be disturbed by other Wi-Fi signals, especially in the vicinity of settlements, so that the range of the radio transmission decreases considerably or even breaks off completely. You must also pay attention to the optimal alignment of the two antennas, especially when flying directly above the controller.
• Control screen: The control screen is a smartphone that is clamped into a special holder on the remote control. As the smartphone is thus coupled to the remote control in terms of orientation, the screen usually points upwards, so that the bright sky is reflected on it and details in the live image are often difficult to recognise. Light-coloured clothing also leads to unsightly reflections.
• Camera: Of course, the camera, which is primarily intended for video recording, cannot be compared with a camera specialised in digital photos. What I noticed negatively was the sensitivity to backlighting and problems with strong differences in brightness.
• Ground clearance:The Mavic Mini does not have a landing gear, but instead rests with the body directly on the ground. This makes off-road take-offs and landings difficult, as there is usually no flat surface. Taking off from a field path or similar from the ground is almost impossible, as there are always plants protruding into the area of the propellers. Furthermore, the Mavic Mini is quite unprotected against dust and moisture, as the development of this drone focused on weight reduction and thus a tight housing is not available. This can be remedied by using a small landing platform, but this has to be carried along as well. Another alternative I use is to take off and land on the outstretched hand, so that no contact with the ground is necessary. With this method, however, you have to be careful not to damage the sensitive camera gimbal.

In summary, after a great 2020 aerial season and 7 months of use in the field, the DJI Mavic Mini has become an indispensable tool for me. However, due to the disadvantages described above, I do not use it exclusively for every purpose. When better camera qualities, greater wind resistance or special tasks (e.g. IR photography) are required, I continue to use the multicopters I have used so far.

Update 2021: At the end of 2020, DJI released the successor model DJI Mini 2. The following key improvements led me to replace the DJI Mavic Mini I had been using, described above, with the new DJI Mini 2:

• The connection between the drone and the remote control now uses the significantly more stable and longer-range OcuSync 2.0.
• The new version of the drone copes much better with gusts and stronger winds up to wind force 5 (16 m/s).
• The camera of the new drone now also provides the recording in RAW format and a simple zooming (unfortunately only digital zoom) during the flight is supported.