Before there were drones, the surveying and documentation of bridges and difficult-to-access structures was a major challenge that demanded alternative methods.
By using drones, precise data can now be acquired from the air, which results in more efficient data acquisition, greater accuracy and more detailed models. The combination of drone technology and photogrammetry has revolutionised the way we at TOPseven acquire 3D models of objects of any type; it has also opened up entirely new opportunities for the inspection, planning and monitoring of infrastructure.
In the following we will consider in more detail the workflow for photogrammetry based on our AI-based navigation and analysis software and clearly explain the steps from the initial images to the complete 3D model.
Planning and Preparation
Careful planning and preparation is crucial before the drone flight. This task includes the selection of a suitable flying area, checking the legal situation, obtaining the necessary approvals, checking the weather conditions, as well as specifying the flight parameters and altitudes.
FLIGHT PATTERN AND IMAGE OVERLAP
Sufficient image overlap is crucial for successful photogrammetry. For this purpose, the drone flies in pre-defined flight patterns above the object or area to be acquired and, during this process, acquires a series of images from different viewing angles. The image overlap ensures that there are sufficient common features between the images for precise measurements and calculations.
GROUND CONTROL POINTS
The use of ground control points is an important step for improving the accuracy of the 3D model. These points are specified reference points on the ground with exact, known coordinates. By identifying and measuring these points in the drone images, precise reference data can be generated that help during the geo-referencing and calibration of the model.
IMAGE PROCESSING AND SOFTWARE
After the images have been acquired by the drone, they must be processed using special image processing software and evaluated. This software automatically detects common features and reference points in the images and reconstructs a 3D model from this information. Various powerful photogrammetry software applications have been developed especially for processing drone images. In this way, at TOPseven we reconstruct a detailed 3D model of the bridge or difficult-to-access structure with the aid of algorithms.
MODELLING AND APPLYING TEXTURE
The reconstructed 3D model, the so-called digital twin, initially consists of point clouds and meshes (grids). Texture can be applied to create a more realistic model. Here the images acquired are projected onto the surface of the model making the model more appealing visually and giving it photo-realistic information.
By combining the virtual and real world, the “digital twin” opens up new opportunities for innovation, optimisation and the improved understanding of complex systems.
ANALYSIS AND EVALUATION
The complete 3D model can now be used for various analyses and evaluations. It is possible to measure lengths, areas and volumes. The model can also be utilised for the inspection of difficult-to-access structures, the identification of damage on quay walls and bridges, or planning construction projects.
Summary
The combination of drones and photogrammetry opens up unexpected opportunities in the world of surveying and modelling. With careful planning, suitable equipment and the right software, businesses in various sectors can profit from the advantages of this technology and make well-informed decisions.
It is this fascinating combination of technology and creativity that inspires us as software developers and helps our customers progress. Always true to our motto: MAKING DRONES SMARTER.
