Geoinformatics FCE CTU

GeoEasy an open source project for surveying calculations

Zoltan Siki — Thu, 23 Aug 2018 00:00:00 +0200

The development of the GeoEasy program started in 1997. Twenty years later in 2017 it became free software under GPL license, version 3.0.0 is freely available for everybody. The core development of GeoEasy is made on Linux operating system, using Tcl/Tk script language, thanks to the Tcl/Tk ports to other operating systems, the program can be run on Linux, Windows, Android and OSX machines. Objectives of the development are to create user friendly graphical user interface (GUI) for surveying calculations in a modular structure with flexible, open connections to other programs. Both educational and professional usages are supported.

Efficient plotting the functions with discontinuities based on combined sampling

Tomáš Bayer — Thu, 23 Aug 2018 00:00:00 +0200

This article presents a new algorithm for interval plotting of the function y = f(x) based on combined sampling. The proposed method synthesizes the uniform and adaptive sampling approaches and provides a more compact and efficient function representation. During the combined sampling, the polygonal approximation with a given threshold α between the adjacent segments is constructed. The automated detection and treatment of the discontinuities based on the LR criterion are involved. Two implementations, the recursive-based and stack-based, are introduced. Finally, several tests of the proposed algorithms for the different functions involving the discontinuities and several map projection graticules are presented. The proposed method may be used for more efficient sampling the curves (map projection graticules, contour lines, or buffers) in geoinformatics.

Plotting the map projection graticule involving discontinuities based on combined sampling

Tomáš Bayer — Thu, 23 Aug 2018 00:00:00 +0200

This article presents new algorithm for interval plotting the projection graticule on the interval $\varOmega=\varOmega_{\varphi}\times\varOmega_{\lambda}$ based on the combined sampling technique. The proposed method synthesizes uniform and adaptive sampling approaches and treats discontinuities of the coordinate functions $F,G$. A full set of the projection constant values represented by the projection pole $K=[\varphi_{k},\lambda_{k}]$, two standard parallels $\varphi_{1},\varphi_{2}$ and the central meridian shift $\lambda_{0}^{\prime}$ are supported. In accordance with the discontinuity direction it utilizes a subdivision of the given latitude/longitude intervals $\varOmega_{\varphi}=[\underline{\varphi},\overline{\varphi}]$, $\varOmega_{\lambda}=[\underline{\lambda},\overline{\lambda}]$ to the set of disjoint subintervals $\varOmega_{k,\varphi}^{g},$$\varOmega_{k,\lambda}^{g}$ forming tiles without internal singularities, containing only "good" data; their parameters can be easily adjusted. Each graticule tile borders generated over $\varOmega_{k}^{g}=\varOmega_{k,\varphi}^{g}\times\varOmega_{k,\lambda}^{g}$ run along singularities. For combined sampling with the given threshold $\overline{\alpha}$ between adjacent segments of the polygonal approximation the recursive approach has been used; meridian/parallel offsets are $\Delta\varphi,\Delta\lambda$. Finally, several tests of the proposed algorithms are involved.

Geodetic work at the archaeological site Tell el-Retaba

Eva Stopková — Thu, 23 Aug 2018 00:00:00 +0200

The paper summarizes the geodetic contribution for the Slovak team within the joint Polish-Slovak archaeological mission at Tell el-Retaba in Egypt. Surveying work at archaeological excavations is usually influenced by somewhat specific subject of study and extreme conditions, especially at the missions in the developing countries. The case study describes spatial data development according to the archaeological conventions in order to document spatial relationships between the objects in excavated trenches. The long-term sustainability of surveying work at the site has been ensured by detailed metadata recording. Except the trench mapping, Digital Elevation Model has been calculated for the study area and for the north-eastern part of the site, with promising preliminary results for further detection and modelling of archaeological structures. In general, topographic mapping together with modern technologies like Photogrammetry, Satellite Imagery, and Remote Sensing provide valuable data sources for spatial and statistical modelling of the sites; and the results offer a different perspective for the archaeological research.

Accurate Measurement of the Riverbed Model for Deformation Analysis using Laser Scanning Technology

Martin Štroner, Rudolf Urban, Tomáš Křemen, Bronislav Koska — Thu, 23 Aug 2018 00:00:00 +0200

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.