DJI Mini 4K: impressions and projects

For the past month, I played around with the DJI Mini 4K drone. In the process, I learned more about drone photography and photogrammetry. I took the drone wherever I went, experimenting with its different features and challenging myself with various small projects to improve my piloting and aerial photography skills.

My first impressions

It’s the most affordable DJI drone, making it a great drone for beginners. While it lacks some features (such as the Obstacle Avoidance System and Waypoint mapping), as a rookie, it won’t be a major concern, and you can make up for the lacking features manually.

Strengths

Learning to pilot is easy, and you get used to it quickly. It knows how to hover on its own based on satellite data, and your only task is to make sure not to fly near trees or obstacles. Even in windy conditions, you won’t have much of an issue! The drone can correct itself in case of strong gusts of wind (up to speeds of 38.5 km/h).
The camera quality is great, capturing photos in 4K resolution with colours popping out well.
The battery is advertised to last for 31 minutes, but from my experience, I get around 25 minutes of flight time in normal mode (sport mode might use more power and cinematic less). I recommend getting the 3-battery pack, from which you can easily get up to one hour of flight.

Flaws

It lacks an Aircraft Obstacle Avoidance System, which could be a problem for beginners. But as long as you fly in open areas until you get more accustomed to flying, it shouldn’t be a problem.
- Return-to-Home (RTH) is decent in open areas… But, due to its missing obstacle avoidance system, you should be careful! I only used the RTH feature once out of curiosity, and the drone almost flew into a tree if I had not taken over control!
No Software Development Kit (SDK) / Flight Waypoint support. Unfortunately, you cannot plan waypoints beforehand with this drone. This may be inconvenient if you want to conduct large-scale photogrammetry because you must do it manually. In my experience, it is still achievable. Otherwise, if you simply want to use this drone for photography, you will not need SDK support.
It has some basic Quickshot filming features, but it’s not its main selling point. A different drone might be better for auto-cinematic recording (for example, the DJI Neo).
The motors can be slightly noisy, especially when it’s windy, and it might annoy some people around. But personally I don’t mind it as much.

After a month of using the DJI Mini 4K, I am really happy with it! Its strengths far outweigh its lack of features (for a beginner). It has a great camera, and it’s easy and fun to take around on trips to capture a bird’s-eye view of the landscape in 4K camera quality or to 3D scan notable monuments or buildings.

Projects

Photogrammetry is the process of stitching together several pictures in order to create a 3D model, a point cloud or an orthomosaic. The photos can be taken with a camera/phone or with a drone (UAV – unmanned aerial vehicle). To stitch photos, digital software can be used (such as WebODM Lightning), which detects common points between the images (creating a point cloud) and generates a 3D model or an orthomosaic.

3D Models. Below is the first 3D model I scanned using a drone: the “Transfăgărășan Semicentennial Monument” (Monumentul Semicentenar Transfăgărășan) that depicts “the man who moves mountains”.

Monumentul Semicentenar Transfagarasan by oticiobanu on Sketchfab

Despite problems with a faulty microSD card at the time, the drone had a feature which saved me: QuickTransfer. Instead of saving the pictures to the microSD card, it transfers the photos via the internet to a phone, at the cost of lower quality images. Nonetheless, it is a good feature to have in cases where storage problems arise.

Orthomosaics are maps composed of several pictures (think of a puzzle). When you use, for example, Google Maps, you are seeing an orthomosaic photographed by different satellites. With the use of a UAV, you can take several pictures from lower altitudes to get more recent and higher-resolution pictures – it’s like your own personal map.