When people think of using drones commercially, they often forget about how robust their uses and payload capacities can be. One of the most popular and useful functionalities is photogrammetry, which refers to the creation of exact maps and models of an area using photographs. Throughout history, photogrammetry was primarily performed by manned aircraft, but these brought with them issues such as bulkiness and cost. With the advent of drone technology, photogrammetry is now cheaper and more accessible. Because of their lightweight design, drones possess enhanced maneuverability, enabling precise image capture and data acquisition. Drone-based photogrammetry integrates sensors affixed to Unmanned Aerial Vehicles (UAVs) with Geographic Information Systems (GIS) to generate detailed maps. This process encompasses not only visual representation but also the measurement of parameters such as distance, angles, and elevation within the map.
The Process
Drone photogrammetry operates on the principle of utilizing multiple images captured from diverse vantage points of a given area, which are subsequently processed through specialized software. This software employs algorithms to iteratively construct a three-dimensional representation of the terrain. Critical to this process is the intentional overlap among the images, even when captured from disparate angles. This overlap facilitates the correlation of features across images, exploiting the subtle variations in perspective inherent in each photograph. This process, known as “image matching,” involves the identification and tracking of specific points or features across the image set, enabling the reconstruction of a comprehensive 3D model from the initially 2D imagery.
Photogrammetry produces diverse 2D and 3D maps, each tailored to address specific challenges. RGB drone data can yield multiple outputs, offering comprehensive views and analytical options. Orthomosaics, precise 2D maps, serve as fundamental base maps in various fields. Point clouds, comprising x, y, z coordinates, form the basis for all outputs, constructed by identifying common points between images. 3D textured meshes connect adjacent points into triangular faces, creating a detailed surface model. Digital surface models (DSMs) capture elevation data, crucial for analyzing terrain features.
Workflows for Photogrammetry
In drone-based photogrammetry, workflows can be categorized into two types: Post-Processing Kinematic (PPK) and Real Time Kinematic (RTK). RTK involves simultaneous image capture and geotagging during flight, offering real-time spatial referencing. Conversely, PPK requires separate image capture and geotagging, with geographic data logged independently. RTK provides immediate, precise spatial data, while PPK yields highly accurate readings post-flight. Each approach offers distinct advantages for different applications in spatial data collection.
Learn more about RTK vs PPK here.
Benefits of Drone Photogrammetry
There are multiple benefits to utilizing drones for photogrammetry.
- Drones facilitate rapid and thorough data collection due to their swift maneuverability.
- Their ability to cover large areas quickly enables high-speed image capture.
- Drones can fly at lower altitudes compared to planes, resulting in more precise data acquisition.
- Entry-level camera drones are cost-effective, reducing the barrier to entry for photogrammetry applications.
The Technology
For conducting effective photogrammetry, the hardware requirements consist of a drone set up with an efficient camera with a good lens, along with typically a low-flying drone. After the photography aspect is covered, software is required to analyze and convert the images into a map or model. This software is integral to the process. DroneDeploy provides accurate mapping and 3D imagery with almost any unmanned aircraft that works with the Global Positioning System (GPS) for positioning.
Applications for Drone Photogrammetry
Drone photogrammetry enables accurate and efficient creation of three-dimensional models and maps for various industries and some of its applications are given below-
- In the energy sector, it assists in assessing oilfields and potential hydropower plant sites, reducing reliance on manpower and expensive survey equipment.
- Engineering firms benefit from precise measurement of structures like bridges and dams, replacing ground-based sensors and accelerating the assessment process.
- Construction sites utilize drone mapping for comprehensive terrain assessment, aiding in project visualization and early detection of building flaws.
- In archaeology, drone photogrammetry offers non-invasive imaging of excavation sites, preserving delicate artifacts while facilitating accurate site mockups.
The Mavic 3 Enterprise and the Matrice 350 RTK are 2 great choices for your mapping needs. The Mavic 3E, armed with a mechanical shutter and RTK module, ensures precise image capture and centimeter-level accuracy, by a thermal variant for specialized tasks. Meanwhile, the Matrice 350 RTK has extended flight time, advanced AI capabilities, and robust redundancy systems, making it versatile for complex mapping scenarios. Understanding this workflow, from pixel capture to map creation, is essential for optimizing efficiency and accuracy in diverse industries, from construction to agriculture.
