Processing and Analyzing Drone Survey Data

Drone mapping is a process of collecting aerial data using unmanned aerial vehicles (UAVs). It includes orthophotography, drone photogrammetry, lidar scanning, and other types of data collection. To understand what the term implies, let's break down all the components of drone mapping. The most common application for processing drone data is photogrammetry.

Images captured by drones are combined with data from an IMU (inertial measurement unit), a GNSS receiver, or GCPs (terrestrial control points) in the field. These images are then stitched together and the data processing software takes care of tasks such as geographically labeling the images and calculating the overlap. The results are then used to create products such as orthophotographs, high-precision maps, and 3D models. This data can be used to measure distances, surface areas, reserve volumes, and other parameters.

Photogrammetry software can also create georeferenced orthomosaics, elevation models, or 3D models of the project area. These maps can be used to extract information such as high-precision distances or volumetric measurements. Reconnaissance drones generate high-resolution orthomosaics and detailed 3D models of areas where low-quality or outdated data is available. This makes it possible to produce high-precision cadastral maps quickly and easily, even in complex or difficult to access environments.

Surveyors can also extract elements from images such as signs, curbs, road signs, fire hydrants, and drains. With 3D mapping software, it is also possible to obtain volumetric measurements from the same images. This fast and inexpensive method of measuring volume is particularly useful for calculating stocks in mines and quarries for inventory or monitoring purposes. Drone images are corrected to detect image distortion and are joined together during post-processing to create a high-precision orthomosaic map. Each pixel contains 2D geographical information (X, Y) and can directly obtain precise measurements such as horizontal distances and surfaces.

Drone images can also be used to create DSM models of the area. Each pixel contains 2D information (X, Y) and the altitude (Z value) of the highest point in this position. The 3D textured mesh is a reproduction of the edges, faces, vertices, and texture of the area photographed by the drone. This model is very useful for visual inspection or when external stakeholders or public participation are essential to a project. With the PPK option, it is possible to achieve absolute accuracy of up to 1 cm (0.4 inches), something that was previously only possible with ground-based reconnaissance equipment. When surveying with drones, images of the ground are taken from multiple observation points.

By processing these images, a photogrammetry software can create orthomosaics and 3D models from which it can measure distance with precision as well as surfaces and volumes of physical objects. After importing or loading the geotagged images into a photogrammetry software such as Propeller, Bentley ContextCapture or Pix4D, the images will be joined together to create 2D or 3D models of the surveyed site. Image processing can be a lengthy process depending on the number of images and the performance of your computer. Some photogrammetry programs are desktop-based and require robust hardware while other software is cloud-based and employs powerful servers instead of your local computer to process the data. A drone study refers to the use of a drone or unmanned aerial vehicle (UAV) to capture aerial data with downward-facing sensors such as RGB or multispectral cameras and LIDAR loads. Aerial images taken by drones greatly accelerate and simplify topographic surveys for land management and planning. As the technological barrier disappeared, digitization and mapping for topographic purposes became one of the main uses of drone cameras. Before starting a mission it's important to check that the drone's battery and connected devices such as tablets are fully charged and that the memory card in the drone's camera has enough empty space to capture the entire project. In this step, the operator basically ensures that no one approaches the drone during takeoff or landing and that the weather conditions remain optimal for the reconnaissance mission.

During a drone study with an RGB camera, the floor is photographed several times from different angles and each image is labeled with coordinates. All of a sudden all the time you saved by switching to drone topography is spent on self-processing and you start again from scratch. Orthomosaic and digital surface model created from aerial images taken by WingtraOne topographic and cartographic drone. Absolute accuracy up to 1 cm (0.4 inches) can be achieved with optimal conditions such as flying above hard surfaces using well-marked highly visible manually measured control points and a well-established base station.