Smart Perspective Capture in the new Zenmuse P1 promises to revolutionize 3D photogrammetry
Geodesy and GIS professionals place the highest demands on the equipment they use. Today, many of them have turned their attention to drones for topographic surveys and 3D modeling. Unmanned aerial vehicles allow you to get results that meet the standards of accurate mapping, at a lower cost and time.
Geodetic surveys using a quadrocopter are a much more difficult task than conventional aerial photography. It includes several stages: preparation of control points, mission planning with the necessary settings, and processing of the obtained images using specialized software. Surveyors are increasingly receiving orders for the construction of orthophotos and 3D models using photogrammetry methods.
The flagship topographic survey kit, the DJI Matrice 300 RTK drone with Zenmuse P1 camera, is the optimal solution in terms of efficiency and accuracy of results. The new Smart Oblique Capture feature takes productivity to the next level. Thanks to what – we will tell in this article!
What is perspective photography?
For perspective aerial photography, cameras with several lenses are traditionally used, simultaneously shooting frames with the same settings in five directions. As a result, the photographs contain details that are invisible when shooting with a camera directed vertically downwards (nadir), which is especially important in the presence of vegetation, or when building models of high-rise buildings.
All five lenses are located in the same housing and are installed with a fixed angle of inclination: one at nadir and four, in most cases, at 45° to the ground and 90° to each other in the horizontal plane.
Benefits of perspective photography
Requirements for the quality and accuracy of 3D models are growing every day. 3D models are used in conjunction with orthomosaics in such serious and important areas as construction work, infrastructure and power grid monitoring, traffic control, environmental pollution and emergency response. The use of photogrammetry methods in geodesy helps to detect potential problems in the early stages of a project and, as a result, avoid significant losses in the future.
Compared to vertical shooting, where a single camera is pointing vertically downwards, perspective shooting has many advantages. If a two-dimensional orthophoto is able to show with high accuracy the coordinates, areas and relative position of objects on the ground, then a three-dimensional model gives a complete picture of the appearance of buildings and natural objects, their location relative to the earth’s surface and the horizon line. Also, visualization of the relief is possible in this way.
Advantages of perspective aerial photography:
- • Detailed visualization of the details of objects, including those located on vertical and inclined planes;
- • Accurate measurement of height and volume of objects, including high-rise buildings;
- • Significantly lesser influence of camera optics distortions on model accuracy;
- • Comparison of data from several images gives greater accuracy when measuring the relative height of a point, the height data can be visualized in the form of a three-dimensional model of the study area.
Limitations of traditional cameras for perspective shooting
It is worth noting that traditional cameras with multiple lenses have a number of disadvantages due to their design features. First of all, such devices are expensive and heavy, which reduces the flight time of the UAV. In addition, the lens installation angle is fixed, it cannot be changed to smaller or larger, which may be necessary for 3D reconstruction of non-standard objects.
Another option is to use one camera on a controlled gimbal. In this case, all the disadvantages of the previous method are absent, however, to solve the same problem, five flights will be required, which increases the specialist’s working time and in most cases requires the availability of spare batteries.
How to combine all the advantages of the two methods to get the job done quickly, efficiently and with high quality?
Smart Oblique Capture function
Smart Oblique Capture is an exclusive feature of the DJI M300 RTK with P1 gimbal. One camera on a controlled 3-axis gimbal performs the same functions as a camera with five lenses. This result is achieved thanks to intelligent software that sets the sequence of actions.
When you define an ROI in the DJI Pilot app, the software will automatically divide it into multiple sections. Sections differ in the number of frames shot with different camera angles. For example, in the center of an area, you need to take five photos (nadir, forward, back, left and right), while on the periphery one angle will be enough.
Since the drone is in motion, the camera does not take pictures at the same time. Smart Oblique Capture takes this into account by incorporating drone speed, camera heading, and aircraft position into each photo’s metadata to eliminate positional and perspective shifts. Automatic mathematical calculations are used to combine all images into an array used in post-processing.
In the video below, you can see the correspondence between the number of shots and the flight speed for the route segment. In green sectors located outside the area, one view is enough to obtain height data. Inside the area, plan shots and perspective photos are added, the number of which depends on the required overlap.
After the mission is completed, you can use software such as DJI Terra to build a 2D orthophoto and 3D model, for which you need to import images from an SD card to a PC or laptop.
The metadata of all frames will be compared for accurate results, nadir images are used to build a 2D topographic plan, and perspective photos are used to build a point cloud and a 3D model.
DJI Terra also allows you to combine the full cycle of work (flight planning and execution, analysis and visualization of aerial photography results) in one program. The software offers the ability to render and visualize data in real time, as well as the fastest post-processing among similar products. Terra creates an accurate orthomosaic and realistic model with a flexible and complete set of navigation, measurement and annotation tools.
Benefits of Smart Oblique Capture (SOC)
- • With the advent of Zenmuse P1, you can abandon heavy and bulky cameras with multiple lenses, the gimbal is mounted on a compact, maneuverable and flexible industrial drone;
- • Artificial intelligence reduces the number of unnecessary shots compared to traditional methods, which allows more efficient use of flight time and space on the memory card, as well as reduce processing time;
- • Interchangeable camera lenses make it possible to choose the focal length based on the specific features of the project;
- • SOC allows M300 RTK users to take full advantage of the PPK (Post Processed Kinematics) method. In situations where RTK is not possible, the exact GNSS coordinates for the PPK are stored in the TimeStamps.MRK files.
More information about Zenmuse P1
The P1 is DJI’s flagship surveying and mapping gimbal. The 45-megapixel camera has a full-frame high-sensitivity low-noise sensor and can be equipped with lenses with a fixed focal length of 24/35/50 mm, mounted on a three-axis gyro-stabilized gimbal. The interval shooting mode allows you to shoot one frame every 0.7 seconds, the shutter speed is up to 1/2000 second, the drone covers an area of 3000 m² per flight.
Learn more about the DJI Zenmuse P1
The Matrice 300 RTK is DJI’s newest and most current industrial flight platform. It has 6 groups of sensors for detection of obstacles in all directions and visual positioning, can be in the air for up to 55 minutes at a distance of up to 15 kilometers (in the FCC standard). During the year of operation, the drone confirmed its high performance, efficiency and reliability and took its place in the fleet of commercial enterprises and government agencies.
Move forward with smart technology
Thanks to intelligent algorithms, SOC allows you to complete a task in one sortie, which previously required 5 missions. Reducing the number of shots makes it possible to use flight time more efficiently and speed up post-processing by 20-50%, depending on the complexity of the project.
Smart Oblique Capture makes the use of drones in surveying and cartography simpler, more efficient and more cost-effective, while maintaining consistently high model accuracy.
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