use of fisheye parrot bebop 2 images for 3d modelling using commercial photogrammetric software

Fisheye camera installed on-board mass market UAS are becoming very popular and it is more and more frequent the use of such platforms for photogrammetric purposes. The interest of wide-angles images for 3D modelling is confirmed by the introduction of fisheye models in several commercial software packages. The paper exploits the different mathematical models implemented in the most famous commercial photogrammetric software packages, highlighting the different processing pipelines and analysing the achievable results in terms of checkpoint residuals, as well as the quality of the delivered 3D point clouds. A two-step approach based on the creation of undistorted images has been tested too. An experimental test has been carried out using a Parrot Bebop 2 UAS by performing a flight over an historical complex located near Piacenza (Northern Italy), which is characterized by the simultaneous presence of horizontal, vertical and oblique surfaces. Different flight configurations have been tested to evaluate the potentiality and possible drawbacks of the previously mentioned UAS platform. Results confirmed that the fisheye images acquired with the Parrot Bebop 2 are suitable for 3D modelling, ensuring accuracies of the photogrammetric blocks of the order of the GSD (about 0.05 m normal to the optic axis in case of a flight height equal to 35 m). The generated point clouds have been compared to a reference scan, acquired by means of a MS60 MultiStation, resulting in differences below 0.05 in all directions

Centimetric accuracy in snow depth using unmanned aerial system photogrammetry and a multistation

Performing two independent surveys in 2016 and 2017 over a flat sample plot (6700 m2), we compare snow-depth measurements from Unmanned-Aerial-System (UAS) photogrammetry and from a new high-resolution laser-scanning device (MultiStation) with manual probing, the standard technique used by operational services around the world. While previous comparisons already used laser scanners, we tested for the first time aMultiStation, which has a different measurement principle and is thus capable of millimetric accuracy. Both remote-sensing techniques measured point clouds with centimetric resolution, while we manually collected a relatively dense amount of manual data (135 pt in 2016 and 115 pt in 2017). UAS photogrammetry and the MultiStation showed repeatable, centimetric agreement in measuring the spatial distribution of seasonal, dense snowpack under optimal illumination and topographic conditions (maximum RMSE of 0.036 m between point clouds on snow). A large fraction of this difference could be due to simultaneous snowmelt, as the RMSE between UAS photogrammetry and the MultiStation on bare soil is equal to 0.02 m. The RMSE between UAS data and manual probing is in the order of 0.20-0.30 m, but decreases to 0.06-0.17 m when areas of potential outliers like vegetation or river beds are excluded. Compact and portable remote-sensing devices like UASs or aMultiStation can thus be successfully deployed during operational manual snow courses to capture spatial snapshots of snow-depth distribution with a repeatable, vertical centimetric accuracy

GEOBIM, BIM integrated geohazard monitoring of at risk slopes and historical retaining structures

Over time, structures such as slopes and retaining walls are increasingly deteriorating, resulting in a risk of collapse. Factors such as climate change, human activities, societal development, rapid growth of cities, increasing population and economy make geological disasters occur more frequently than usual. Geological hazards of nature, slope collapse, slope fractures or slope movements have become a problem to be solved by civil engineering. With the advent of low-cost sensors, optical topographic surveying and BIM (Building Information Modelling), such risk could be mitigated and, in some cases, eliminated. The main aim of this research was to use wireless sensors to monitor slopes that are potentially at risk and to incorporate all the information obtained in BIM (Building Information Modelling), in order to make a digitalized vision of the structures in real time. High precision and innovative tools, such as drone flights and slope scanners were utilized for a detailed analysis of the risk of change in the geohazards including soil slopes and historic retaining walls. Through the combination of data from sensors with point clouds generated from drone flights, an early warning system was developed. This early warning system was clearly able to display when there was surface changes therefore highlighting the areas of high risk of collapse. This thesis shows how continuous real-time surveillance of soil slopes and retaining walls can be achieved clearly and concisely, in a cost-effective manner

FORENSIC ENGINEERING SURVEYS WITH UAV PHOTOGRAMMETRY AND LASER SCANNING TECHNIQUES

This work aims at presenting the use of new technologies in the field of forensic engineering. In particular, the use of UAV photogrammetry and laser scanning is compared with the traditional methods of surveying an accident site. In this framework, surveys must be carried out promptly, executed in a short time and performed so that the greatest possible amount of information is collected with sufficient accuracy to avoid the possibility of neglecting details once that the scene is no longer preserved. The combination of modern surveying techniques such UAV photogrammetry and laser scanning can properly fulfill these requirements. An experimental test has been arranged and instruments, procedures, settings, practical limits and results have been evaluated and compared with respect to the usual way of performing the survey for forensic purposes. In particular, both qualitative and quantitative considerations are given, assessing the completeness of the reconstructed model, the statistical evaluation of the errors and the accuracy achieved

Innovative Tools For Planning, Analysis, and Management of UAV Photogrammetric Surveys

The Unmanned Aerial System (UAV) is widely used in the photogrammetric surveys both for structures and small areas. The geomatics approach, for the several applications where the 3D modeling is required, focuses the attention on the metric quality of the final products of the survey. As widely known, the quality of results derives from the quality of images acquisition phase, which needs an accurate planning phase. Actually, the planning phase is typically managed using dedicated tools, adapted from the traditional aerial-photogrammetric flight plan. Unfortunately, UAV flight has features completely different from the traditional one, hence the use of UAV for photogrammetric applications today requires a growth in the planning knowledge. The basic idea of the present research work is to provide a tool for planning a photogrammetric survey with UAV, called \u201cUnmanned Photogrammetric Office\u201d (U.Ph.O.), that considers the morphology of the object, the effective visibility of its surface, in the respect of the metric precisions. The usual planning tools require the classical parameters of a photogrammetric planning: flight distance from the surface, images overlaps and geometric parameters of the camera. The created \u201cOffice suite\u201d U.Ph.O. allows a realistic planning of a photogrammetric survey, requiring additionally an approximate knowledge of the Digital Surface Model (DSM) and the attitude parameters, potentially changing along the route. The planning products will be the realistic overlapping of the images, the Ground Sample Distance (GSD) and the precision on each pixel taking into account the real geometry. The different tested procedures, the solution proposed to estimates the realistic precisions in the particular case of UAV surveys and the obtained results, are described in this thesis work, with an overview on the recently development of UAV surveys and technologies related to them

Photogrammetric suite to manage the survey workflow in challenging environments and conditions

The present work is intended in providing new and innovative instruments to support the photogrammetric survey workflow during all its phases. A suite of tools has been conceived in order to manage the planning, the acquisition, the post-processing and the restitution steps, with particular attention to the rigorousness of the approach and to the final precision. The main focus of the research has been the implementation of the tool MAGO, standing for Adaptive Mesh for Orthophoto Generation. Its novelty consists in the possibility to automatically reconstruct \u201cunrolled\u201d orthophotos of adjacent fa\ue7ades of a building using the point cloud, instead of the mesh, as input source for the orthophoto reconstruction. The second tool has been conceived as a photogrammetric procedure based on Bundle Block Adjustment. The same issue is analysed from two mirrored perspectives: on the one hand, the use of moving cameras in a static scenario in order to manage real-time indoor navigation; on the other hand, the use of static cameras in a moving scenario in order to achieve the simultaneously reconstruction of the 3D model of the changing object. A third tool named U.Ph.O., standing for Unmanned Photogrammetric Office, has been integrated with a new module. The general aim is on the one hand to plan the photogrammetric survey considering the expected precision, computed on the basis of a network simulation, and on the other hand to check if the achieved survey has been collected compatibly with the planned conditions. The provided integration concerns the treatment of surfaces with a generic orientation further than the ones with a planimetric development. After a brief introduction, a general description about the photogrammetric principles is given in the first chapter of the dissertation; a chapter follows about the parallelism between Photogrammetry and Computer Vision and the contribution of this last in the development of the described tools. The third chapter specifically regards, indeed, the implemented software and tools, while the fourth contains the training test and the validation. Finally, conclusions and future perspectives are reported

Evaluation of the laser response of Leica Nova multistation MS60 for 3D modelling and structural monitoring

The use of Terrestrial Laser Scanner (TLS) is quite common for architectural surveys, however it requires to arrange special targets on the scanned object and to acquire several overlapping scans, which have to be aligned and edited externally. Recently, Leica released on the market a new kind of instrument, known as MultiStation (MS). It includes both the main characteristics of a TLS and of a Total Station (TS), meaning that no targets are required for the scan alignment, since the whole survey can be directly georeferenced. In this paper, some analyses about the use of this instrument for 3D modelling applications are discussed. First of all, the laser signal response is evaluated considering different materials, acquired using several combinations of distances and incidence angles. Then, the survey of the Casalbagliano Castle is presented and analyzed. All the performed tests show the great potentiality of the MS, allowing to reach accuracies of the order of few millimeters