This paper presents a Wavelet Neural Network (WNN) employment for discrete precise ephemerides tabular data of Global Navigation Satellite System (GNSS) orbit approximation to obtain continuous orbit function. Orbit function is essential in positioning and navigation tasks, the advantage of continuity, however, is that it can also be used during GNSS signal interruptions. The essence of WNN continuous orbit construction is single function determination for the entire interval, while the interpolation methods follow several discrete function establishment. Specifically, we investigate the performance of the WNN continuous orbit approximation by comparison with well known polynomial and trigonometric interpolations. The experimental results show that our proposed method is superior to the traditional methods especially near the end of intervals, because they are not subject to large scale function oscillations as in the case of polynomials constructions. We propose a WNN construction using different mother functions of the WNN namely Mexican hat, Morlet function, Gaussian and Daubechies (D4) wavelet. Furthermore best algorithm for regression estimation is described; selection of neurons in the hidden layer of WNN is based on orthogonal least squares algorithm. The main objective of this article is to show that the presented method of orbit function construction could be used for GNSS ephemerides distribution and short-time prediction in the Assisted GNSS-networks.
COBISS.SI-ID: 6122081
Independence of observations is often assumed when adjusting geodetic network. Unlike the distance observations, no dependence of environmental conditions is known for horizontal irection observations. In order to determine the dependence of horizontal direction observations, we established test geodetic network of a station and four observation points. Measurements of the highest possible accuracy were carried out using Leica TS30 total station along with precise prisms GPH1P. Two series of hundred sets of angles were measured, with the first one in bad observation conditions. Using different methods, i.e. variance–covariance matrices, c2 test and analyses of time series, the independence of measured directions, reduced directions and horizontal angles were tested. The results show that the independence of horizontal direction observations is not obvious and certainly not in poor conditions. In this case, it would be appropriate for geodetic network adjustments to use variance–covariance matrix calculated from measurements instead of diagonal variance–covariance matrix.
COBISS.SI-ID: 5871713
Geometric leveling is the most precise and universal method used to determine heights. In order to achieve the greatest possible accuracy, the method demands a calibrated leveling staff, which requires an appropriate calibrationfacility. The encoded shape of the leveling staff demands the rebuilding of comparators designed for calibrating classical leveling staffs. The comparator MSGL001 at the Faculty of Civil and Geodetic Engineering in Ljubljana is based on an optical encoder system that is an original solution of snapshot positioning. The aim of this paper is to present the rebuilt comparator and the details of its testing.
COBISS.SI-ID: 6312545
This study provides an interdisciplinary account determining how children and adolescents understand urban and architectural aspects of sustainable development. The concept of sustainability implies complex relations between ethical, economical, social, technical and other qualities of our environment. The concept is difficult to understand for children who lack the abilities of abstract reasoning and multi-dimensional thinking. A new measure of sustainability understanding was formed based on pictorial rather than textual format and was applied to a large sample of over 2000 participants aged 6-19 years. The results indicated that girls had higher levels of appreciation toward sustainability issues than boys. The results also showed that understanding of sustainability issues increased progressively with age, particularly with adolescents from urban environments. The findings are discussed in terms of cognitive changes in adolescence and their implications for educational policy.
COBISS.SI-ID: 5360737
Many real-world spatially related problems, including river-basin planning and management, give rise to geographical information system based decision making, since the performance of spatial policy alternatives were traditionally and are still often represented by thematic maps. Advanced technologies and approaches, such as geographical information systems (GIS), offer a unique opportunity to tackle spatial problems traditionally associated with more efficient and effective data collection, analysis, and alternative evaluation. This paper discusses the advantages and challenges of the use of digital spatial data and geographical information systems in river basis management. Spatial data on social, environmental and other spatial conditions for the study area of 451.77 km2, the Slovenian part of the Sotla river basin, are used to study the GIS capabilities of supporting spatial decisions in the framework of river basin management.
COBISS.SI-ID: 512519485