Can the DJI Mini 2 Be Used for Mapping? (Quick Answer)
When it comes to choosing the right tool for the job, knowing the capabilities and limitations is the first step.
The DJI Mini 2 may not be the most appropriate drone for commercial mapping and surveying use, although it can capture quality photographs needed for creating aerial maps and will help you learn the fundamentals of how mapping using drones works.
If the DJI Mini 2 is your first drone and you’re exploring all the various applications and uses for it, you have likely come across surveying and orthomosaic mapping. Essentially, creating an orthomosaic map starts with capturing detailed photographic images of a building or land. Then, using software to analyze those images, you generate a hyper-realistic model that can be used for further analysis.
Fortunately, the Mini 2 excels at taking high-quality photographs! Unfortunately, it is not likely that the DJI Mini 2 will be added to approved drone lists for commercial or industrial mapping applications even though it can be used to learn the fundamentals of orthomosaic mapping.
In fact, with recent software updates, the Mini 2 is now capable of improved image capture programming. With the use of 3rd party flight applications, like Litchi, the capabilities of this little powerhouse have been expanded to include automated flight paths through the use of waypoints.
Automated flight planning is a core component of capturing images for generating orthomosaic maps. It provides for the consistency and efficiency required for the best possible output.
This article does not fly too far into the high-end software solutions nor compare all the drone systems available for mapping at a commercial level. However, I will highlight the fundamentals that will enable you to scratch the surface of the mapping process with your Mini 2.
Drone specifications for mapping
The first step in creating an orthomosaic map using a drone is capturing the high-resolution photographs required to generate a detailed map or model. While the Mini 2 is very capable and captures beautiful photos and video content, there are far better tools for the job.
Commercial uses of drones for mapping benefit from the combination of high camera resolutions that can efficiently fly over hundreds or even thousands of acres of land during a project. Given these requirements, the 12MP camera on the Mini 2 falls a bit short of the more optimal 20MP camera that the Mavic 2 Pro or Phantom Series brings to the table, for example.
Many commercial applications for mapping rely on even larger drones such as the Inspire or Matrice due to more capabilities and options for different cameras or imaging devices. These larger systems also perform better generally in adverse weather as well as being able to stay in the air longer before recharging.
Battery capacity and flight time are significant considerations for efficiently capturing photos of large tracts of land or expansive facilities. Larger, more expensive drones have longer flight times due to higher capacity batteries. This enables them to capture more images per charge and cover more acres per day, making them preferred systems over the Mini 2.
Finally, another aspect of the Mini 2 is its physical size and weight, decreasing its performance in higher winds than its larger counterparts. Again, efficiency in the field is a primary concern when selecting a drone for commercial or industrial mapping work.
Even with these technical and physical limitations, the Mini 2 does otherwise have sufficient technical specifications and features to capture the images needed to generate an orthomosaic map. There are a lot of software solutions out there to create an orthomosaic map. Typically, recommendations for photo quality suggest the best possible output from utilizing the following parameters.
Orthomosaic mapping basics
The first consideration is the volume of photos you need to capture, and the camera and gimbal settings. You will need photo coverage of at least 70% overlap. The DJI Mini 2 has a 24mm equivalent camera lens, considered wide-angle and great for capturing landscape photos.
For full coverage and to capture the detail needed for orthomosaic imagery, you achieve this by flying a grid pattern and selecting the automatic photo capture setting to 5 seconds. The current version of the DJI Fly app does not support fully autonomous flight programs available in the larger drone systems. However, the DJI Fly app does support automatic photo capture intervals.
Along with setting the gimbal angle to ~45 degrees, you simply need to focus on flying the Mini 2 manually through a grid pattern while the software captures the photos. You just need to ensure that your grid pattern creates enough overlap on each pass to get full coverage. This may take some trial and error passes to get it right, but with the right speed, and attention paid to your flight grid, you will capture enough images to produce a map.
How to create a map with Mini 2 using Litchi
If you are using Litchi as a flight app, a recent software update has added waypoint flight programming support for the Mini 2. Map out your grid pattern using waypoints, specify flight altitude, photo capture intervals, and other settings.
This leaves you to focus on monitoring your drone as it completes the mission. It is highly recommended to first test the automated flight programs in a wide-open field, to avoid potential crashes while you learn how the program works.
Even for just an acre of land, the process may take hundreds of photos, such that any single point on the ground may be found and analyzed across dozens of photos. Another rule of thumb is that you want your flight altitude to be roughly five times the height of the tallest object in your subject area. This means that if the trees are 50 feet tall, your flight altitude should be ~250 feet above ground level (AGL).
It is always a good idea to practice in an area with little or no obstructions so that you can focus on flying the grid pattern at a constant speed and altitude. Software and hardware features available for drones like the Mavic 2 Pro and Phantom Series make them capable of accounting for elevation changes. They also have advanced cameras and obstacle avoidance systems to aid them in avoiding collisions with trees or structures.
One last note about your settings to capture your photos with the Mini 2 is that you will need GPS metadata enabled. This is fundamental to how the orthomosaic software works in stitching together realistic maps from your photos.
How to generate an orthomosaic map
There are dozens of software packages available for consumers to generate orthomosaic maps from the images they capture. Many commercial software packages offer free trials for testing, with some even providing the proprietary software to fly the autonomous flight to capture the images.
Pix4D and Drone Deploy are a couple of popular commercial solutions that offer image processing and map generation as part of their trial period, up to a certain number of images or maps. Currently, the flight planning apps from these providers do not support the Mini 2. That said, the map generation software just needs the photo images with GPS coordinates to stitch together a map.
The steps to generating the map are generally the same with most available software packages, though there may be some differences. More sophisticated software packages, those that typically require paid subscriptions, do more of the processing automatically and simply leave your work to capturing, uploading, and clicking generate.
Also, several open-source solutions are available that require a few more choices and selections to be made, but the concepts are similar. The key is finding the right solution for the type of computer you have, as many are only supported by either Windows or Mac.
1. Upload photos
First, you need to upload all the photos you captured during your flight. This could be hundreds of photos, so the amount of time this process takes is generally related to your internet and computer speeds.
2. Decide which processes to use
Once your files are uploaded, you will need to begin the processing that generates the orthomosaic map. There are a few concepts to understand to get the results you are looking for. These concepts include Point Clouds, Dense Clouds, Mesh or Digital Elevation Models (DEM), and Texture Maps.
Point Cloud generation essentially creates all the data points in space that represent the 3D shapes and objects from the photographs to generate your orthomosaic map. This is done by the software recognizing overlapping elements from the images and calculating spatial differences between them.
This is a processing-intensive step that may take several minutes or hours to complete, depending on the number of photos and your internet connection. When viewing a point cloud, you may be able to discern elevations and objects, but the details you would see in your photos are not applied yet.
Dense Clouds utilize comparisons of multiple images and measure the points between them to more accurately create the model from your photographs. This is where the consistency of your flight pattern and photo capture comes into play through the camera angles, distances, and overlaps.
Mesh and DEM modeling use the previous outputs to interpolate and generate the elevations and a more detailed view of the terrain you captured.
Texture Mapping will fill in all the details from your photos that make the model look realistic.
3. Generate the map/model
The resulting 2D/3D image generated from these processes is your final result. The final quality of your model will depend on the quality and volume of photographs and the capabilities of the software used.
Depending on the features available in the software, you may have other features such as measuring distances that were calculated through these processes. At a minimum, you should be able to explore your map by zooming, tilting, and spinning to see the landscape from different views. Exploring your final map is your reward for all the work put into it.
Cover photo by Nathan Dumlao