Summer, 2019 was my first encounter with drones and aerial photography. I worked with Daniel Rubenstein’s Lab at Princeton University to capture RGB (regular photo) and NIR (Near Infrared) imagery of local farms. For this work, I operated a DJI Phantom Pro 4 v2. You can read more about that experience here.

I’ve been extremely interested in aerial imagery and drones since that time. Until now, I’ve worked with a variety of public aerial imagery and GIS (Geographic Information Systems) files for environmental engineering and epidemiological applications associated with my academic studies. The breadth, quality, and accessibillity of public GIS data is frankly astounding. But I’ve always been interested in producing my own data at extremely high resolutions. I’ve also been interested in photography, and a camera with wings is very appealing.

Enter the DJI Mini SE! After a few discussions about drones with my Dad prior to Christmas, he went searching for economical drones and discovered this recent release by DJI: the Mavic Mini SE. My parents gifted me with the Mini SE, and my dad soon thereafter purchased a Mini 2 (slightly better drone) of his own.

In this post, I review my experience with the DJI Mini SE so far, share a few raw images and videos taken with the little machine, and list remarkable GIS products that can be derived from SE aerial imagery. Let’s dive in!

🌿 My Drone, “Asher”

Drone photo

I named my drone “Asher,” which means “Happy” or “Blessed” in Hebrew: אָשֵׁר . אָשֵׁר is the first word in the Psalms and the name of one of the sons of Jacob (Genesis 30:12-13). I named the drone Asher (אָשֵׁר) because of its small, gentle size and happy buzz when it flies.

I decided to paint my drone with a variety of bright colors to match its name. I used cheap acrylics from an art store, and they worked nicely.

🚁 DJI Mini SE: specs and experience

The DJI Mini SE is a starter drone, which means that its camera and flight capabilities are towards the lower end for consumer photography drones. That being said, the Mini SE is a DJI product (DJI is the company, see here), and DJI produces phenomenal drones; this means that the Mini SE is equipped with state-of-the art camera gimbal and rotor technology, which enables extremely smooth and trustworthy flight and photography.

🦾 Body

The Mini SE is a quadcopter, which means that its propulsion and stabilization are managed by a set of four (“quad”) rotors. On the Mini SE, each rotor is attached to two propellor blades. Each blade is shaped as a tiny airfoil designed to meet the specific needs of the aircraft (see interview with propellor engineer here). The Mini SE propellors are 4726FM, or 4.7in diameter and 2.6in pitch (which means that the propellor would travel down 2.6 inches in one revolution if traveling through a soft solid).

Drone props

The Mini SE weighs in just below 250 grams. This is true for all Mavic Mini drones. Why the 250g cutoff? According to the Federal Aviation Administration, drones weighing less than 250g are not required to be registered. Sub-250g drones (the DJI Mini lineup, among others) are therefore free from any red tape. The tiny weight of the Mini SE is also great for carrying it around in a backpack or carrying case.

The Mini SE packs up tight for transportation. When unfolded, the Mini SE is three times as wide and almost twice as long as its packed-up configuration.

Drone configs

The Mavic Mini drone body is made of rigid plastic polymer; lightweight and hard, probably built for a bit of impact (but not much). My drone has already taken a few tumbles (because I ran it into the wall in my living room) and it fared just fine with minimal damage to the propellors and no body damage.

I find the drone body to be well sized for a pack-it-wherever-you-go-adventuring drone. It fits easily into a small bag or tucked into your backpack and unfolds effortlessly. The drone body design is, in my opinion, phenomenal, and I expect it to last a long time. I also enjoyed painting the body of my drone and found that basic acrylic paint works well. Tons of skins are also available for purchase.

📷 Camera

The Mini SE has a decent camera for beginner aerial photography. I’ve been well pleased with the quality of both photos and videos taken with the little aircraft. The colors are especially vibrant and pleasing.

The camera is mounted at the front of the aircraft on a three-axis gimbal. This gimbal controls the yaw (axis one, which is the in the plane of the image), the pitch (axis two, which is the “up and down”), and the roll (axis three, rotation of the image about its center) of images (click here for a better description of these axes). Effectively, this means that the camera is stabilized against any motion of the aircraft.

So far, the image stabilization I’ve experienced while flying the Mini SE is incredible. While both hovering and moving, still images and video are practically unaffected by chaotic motions in the wind or aircraft. I have only experienced turbulent video in especially high winds.

Drone camera

The camera sensor is 1/2.3” CMOS, which, in the camera world, is one of the smallest out there. It shoots 12MP photo at resolutions of 4:3: 4000×3000 and 16:9: 4000×2250. The drone also shoots 2.7k video at 30 fps (frames per second), which is equivalent to 2720×1530 resolution.

For a full list of camera specifications (including focal length, iso, etc.) check out the official Mini SE specs page. Note that the Mini 2 drone, which has a higher pricepoint than the Mini SE, has an identical camera but can shoot 4k video. So the Mini SE video capabilities (as well as some flight capabilities) are throttled by software in order to drive people to purchase the Mini 2.

All in all, I’ve been really pleased by the Mini SE camera. Here’s an example image shot by the Mini SE. Scroll down further for more images and some video examples.

Image

🦅 Flight: battery and transmission constraints

The Mini SE max flight time and distance are constrained by two equally important features: battery life and controller transmission strength. The SE battery is rated for 30 minutes flight at 17kph in windless conditions. My experience is approximately 20 minutes of flight maximum (there’s always wind!). The Mini SE starts screaming at you (the controller beeps loudly and rapidly) when your battery falls below 20% in flight and increasingly rapidly as the battery falls below 10%. On regular excursions, I never take the drone more than 40% battery-wise in one direction, because then it will be at 20% when I return to the takeoff location (40% out and 40% back is 80% battery consumed during flight).

The second flight distance constraint is transmission strength. This is where the Mini SE is a particularly “beginner” drone. The remote control and drone use “enhanced wifi” to communicate, which operates in the 5.725-5.850 GHz range. Ostensibly, this signal has a range of 4 kilometers if no obstructions are present between the controller and the drone. In my experience, transmission becomes intermittent around 1km. I find that angling the antannae of the remote so that they intersect perpendicularly with the direction of the drone helps to increase signal strength and becomes essential at distances greater than 3/4 km.

The Mini SE flies and handles extremely well. It hovers dependably if it has strong GPS signal strength and bright lighting conditions but can drift if one or both of the GPS or lighting conditions are poor. The Mini SE controls are sensitive and the drone can therefore be tightly maneuvered through space. My only crash has been due to drift while hovering indoors (which meant both poor GPS signal and poor lighting).

All in all, the Mini SE is tons of fun to fly. I find myself wanting to put it up in the air whenever the battery is fully charged.

🌄 Sample pictures and video

Drone - DJI Mini SE, "Asher"

🗺 Derivable GIS Products

If you angle the Mini SE gimbal so that it faces straight down and fly the drone around in a small area so that it takes overlapping photos of a space from different angles and altitudes, then the resulting images can be used with OpenDroneMap (ODM, see here) software to produce georeferenced products. These products include:

  • Orthorectified geotif (.tif)
  • 3D georeferenced textured mesh model of terrain and objects
  • 3D point cloud of terrain and objects
  • Digital elevation model (DEM)

These products can be used for detailed geospatial analysis (such as surveying or municipal planning) or for tracking changes in a landscape over time (such as for forestry or agriculture).

👋 Salutation

Thank you for stopping by and reading this post! I hope you found it interesting and informative. May the peace of Christ Jesus be with you.