K. Bakuła

Evaluation of the accuracy of lidar data acquired using a UAS for levee monitoring: preliminary results

ABSTRACT This article presents the preliminary results of the possibilities for using an unmanned aerial system (UAS) for three-dimensional (3D) data collection for levees. The UAS is equipped with an ultra-light laser scanner and digital camera that acquires data with stereoscopic coverage. Sensors have been mounted on the multi-rotor. Using such a platform allows obtaining the 3D data necessary for circular surveying works with regard to levee monitoring for the prevention of flooding. Such a platform can offer an alternative to typical direct surveying measurements performed during the monitoring of such objects. It can detect changes in the multi-temporal analysis and evaluate the condition of levees ought to continuity of surface measurement and huge density of data up to dozens points per square metre. Lidar data and images of the levees were provided for several hundred metres of test area. In presented research, several flying missions were carried out which provided data that allowed for an analysis presenting the influence of the technique for initial georeferencing, altitude over the terrain, scanning lines’ length, overlap between scanning lines on the accuracy of relative orientation and absolute accuracy of the digital terrain model (DTM) that was created. The Iterative Closest Point algorithm and measurements of the natural and signalized control points were used to georeference and validate the lidar data obtained from the UAS. As reference data, Global Navigation Satellite System in real-time kinematic measurements was used to evaluate the absolute accuracy of the DTMs generated for the test area. The images captured from the UAS were a different data source which was checked to evaluate their usefulness in the considered application. A final accuracy close to 0.1 m was obtained for the generation of the DTM. The research proved the potential of this new kind of lidar data that can be acquired using ultra-light laser scanners.

Influence of Elevation Data Source on 2D Hydraulic Modelling

The aim of this paper is to analyse the influence of the source of various elevation data on hydraulic modelling in open channels. In the research, digital terrain models from different datasets were evaluated and used in two-dimensional hydraulic models. The following aerial and satellite elevation data were used to create the representation of terrain–digital terrain model: airborne laser scanning, image matching, elevation data collected in the LPIS, EuroDEM, and ASTER GDEM. From the results of five 2D hydrodynamic models with different input elevation data, the maximum depth and flow velocity of water were derived and compared with the results of the most accurate ALS data. For such an analysis a statistical evaluation and differences between hydraulic modelling results were prepared. The presented research proved the importance of the quality of elevation data in hydraulic modelling and showed that only ALS and photogrammetric data can be the most reliable elevation data source in accurate 2D hydraulic modelling.

Diversity of Photogrammetric Approaches for Multi-Purpose Applications

Abstract The presented paper shows the diversity of photogrommetric approaches by introducing a problem of camera interior orientation, data georeferencing. data integration and the issue of automatic object surface modelling. The authors discuss the abovementioned issues on the example of the work carried out at the Faculty of Geodesy and Cartography, Warsaw University of Technology referring to solutions practiced in Computer Vision. This article is an example of introduction of photogrammetry as a discipline open to achievements of close fields of science, which is widely applied in practice