Bronislav Koska

This paper presents an interesting application of the riverbed model shape and deformations monitoring using laser scanning technology and accurate local micro-network. The most interesting fact about this application is very high accuracy demand on deformation determination (maximum permissible error is only 2 mm) within quite large object (the size of the riverbed model is about 100 meters). Up to now, mechanical calipers in the selected profiles were used to detect the changes. This manual approach is very laborious and time-consuming and the gathered data resolution and accuracy is often not sufficient. The suggested solution contains two main parts. The first part deals with construction of highly accurate local micro-network for laser scanning needs (maximum required standard deviation in any coordinate is lower than 0.4 mm) and the second part deals with actual laser scanning and data processing. Design, measurement and processing of the experiment was conducted for the needs of the research project “Improvement of navigation conditions on the Elbe between Ústí nad Labem - state border CR / FRG - Navigation Step Děčín”. The main goal of this project is design and realization of the river regulation to improve the navigation conditions. The key benefit of using river model is the possibility to easily simulate various catastrophic scenarios (various degrees of the floods) and their impacts on riverbed changes.

In this article, the autonomous mapping airship (AMA) equipped with lidar along with its basic properties is introduced. Other methods and technologies using unmanned aerial vehicles (UAVs) or conventional aircraft are then compared to the AMA. Specifically automatic reconstruction from photographs acquired with fixed wing UAVs and lidar taken from conventional aircraft. Comparison of technologies was realized in the locality of a brown coal mine spoil heap. The size of the spoil heap interest part is about three square kilometres and it is covered with wind-blown vegetation (trees, grass, bush). We also measured about 100 height check points (HCPs) using real-time kinematic Global Navigation Satellite System technology for the purpose of accuracy analysis in the locality. One group of the HCPs were measured on the vegetation-free ground and the second group on ground with low vegetation (grass). Other properties of the methods used and the data acquired were also compared. The most important of these were data density, vegetation penetrability, speed of data collection, and economical aspects.

Keywords: Laser Scanning, Structure from Motion, Texture, Orthophoto, Orthoimage, Photogrammetry Terrestrial laser scanning technology is used for creation of building documentation and 3D building model from its emerging at the turn of the millennium. Photogrammetry has even longer tradition in this field. Both technologies have some technical limitations if they are used for creation of a façade or even an interior orthophoto, but combination of both technologies seems profitable. Laser scanning can be used for creation of an accurate 3D model and photogrammetry for consequent application of high quality colour information. Both technologies were used in synergy to create the building plans, 2D drawing documentation of facades and interior views and the orthophotos of St. Nicholas Baroque church in Prague. The case study is described in details in the paper.

The aim of the project is to create measuring system with specific properties suitable for effective mapping of medium-wide areas (units to tens of square kilometers). The system should be useful especially for ranges that are too large for conventional surveying with GNSS or total station and too small for use of manned air vehicles from economical and accuracy point of view. Accessories of the system will allow e.g. collecting data for urban area modeling, creating thermometric georeferenced maps, mapping of dangerous or inaccessible areas (damps, open-pit mines). For this reason the platform is equipped with laser scanner, VIS camera (one for vertical capturing or more for slope capturing), thermo camera and INS/GPS as an exterior orientation (pose) determination unit. Especially in task of urban modeling the airship, as carrier, have legislative advantages due to prepared restriction for UAV. The resulting absolute accuracy of the developed system should be better than 10 cm (position standard deviation) and the random component is less than 5 cm. This accuracy is lower than for conventional measurements, but significantly higher than the scanning system carried by piloted aircraft. In terms of properties (accuracy, speed of data collection) our system is close to the terrestrial mobile scanning systems, which has disadvantage in the lack of availability in hard to reach locations.