High industrial chimney inclination monitoring and analysis is crucial from a stability point of view because, if not maintained, it can pose a great potential hazard for its surroundings. Various ...modern approaches of chimneys’ geometrical parameters determination have been proposed and are actively in use. However, little research regarding the applicability of the unmanned aerial system (UAS)-based photogrammetric approach of chimney structural monitoring has been conducted and a comprehensive analysis with validated methods is lacking. Therefore, this research is focused on the determination of geometrical structural parameters of a masonry chimney whereby two independent methods have been applied. Reference values of the chimney geometrical parameters have been determined by precise total station (TS) measurements and, in relation to them, the applicability of the UAS-based photogrammetric approach is evaluated. Methodologically, the reference and validation values of the chimney geometrical parameters have been determined based on double modeling of the chimney structure. Firstly, cross-sectional elliptical regression has been applied to determine the geometrical values of the chimney at predefined above-ground levels (AGLs). Secondly, the spatial chimney axis has been derived by polynomial regression to determine the inclination of the full chimney structure. Lastly, the structural stability of the chimney is validated based on its axis inclination whereby permitted deviations are determined according to the European Standard EN 1996-1-1:2005. Experimental results of our research show that consistently better results are gained by TS-based surveys and, although the determination of the chimney’s geometrical values by the UAS-based approach is certainly possible, great attention must be given to the accuracy of the UAS-generated point cloud (PC) if high accuracy results are needed.
Besides precise levels, precise leveling staffs are a crucial part of the measuring equipment when carrying out geodetic (geometric) leveling measurements. The leveling staffs define the scale of the ...height reference system, so it is important to calibrate them periodically and when necessary. This paper shortly describes the development of the new method of calibrating leveling staffs in the Laboratory for Measurements and Measuring Technique of the Faculty of Geodesy, University of Zagreb. The existing horizontal comparator was upgraded by installing a servo-motorized positioning drive with a mounted CCD camera and telecentric lens that is used to record graduations of the leveling staffs. The software was developed to support the management of the comparator system, as well as for the analysis and processing of images and measurement data and, most importantly, giving the result in the form of a calibration report. The main subject of this paper is a detailed assessment of the measurement uncertainty of determining the position of the edges of the graduation lines and determining the scale of precise centimeter and coded leveling staffs. The estimates were confirmed by experimental measurements.
For high-precision Global Navigation Satellite Systems (GNSS) positioning based on carrier-phase measurements, knowledge of the GNSS receiver antenna electrical signal reception characteristics, ...i.e., phase center, is crucial. Numerous studies have led to the understanding of the influence of GNSS receiver antenna phase center corrections (PCCs) on GNSS positioning accuracy and other estimated parameters (e.g., receiver clock estimates, ambiguities, etc.). With the goal of determining the PCC model of GNSS receiver antennas, only a few antenna calibration systems/facilities are in operation or under development worldwide. The International GNSS Service (IGS) publishes type-mean PCC models for almost all geodetic-grade GNSS antennas. However, the type-mean models are not perfect and do not fully reflect the signal reception properties of individual GNSS receiver antennas. Relevant published scientific research has shown that the application of individual PCC models significantly improves the accuracy of GNSS positioning and other estimated parameters. In this article, the new automated GNSS antenna calibration system, recently developed at the Laboratory for Measurements and Measuring Technique (LMMT) of the Faculty of Geodesy of the University of Zagreb in Croatia, is presented. The developed system is an absolute field calibration system based on the utilization of a Mitsubishi MELFA 6-axis industrial robot. During calibration, the robot tilts and rotates the GNSS antenna under test (AUT) around a fixed point within the antenna. The antenna PCC modelling is based on time-differenced double-difference carrier-phase observations. Our preliminary results for the Global Positioning System (GPS) L1 (G01) frequency show a submillimeter repeatability of the estimated PCC model and a submillimeter agreement with the Geo++ GmbH calibration results.
Renewable energy is one of the main components of a sustainable world and its future. The consumption of electricity from renewable sources in Croatia has an impressive rate of 53.5%, but offshore ...wind turbines (OWT) have not yet been installed in the Adriatic Sea. The aim of this study is to determine the possibilities for offshore wind farm (OWF) positioning in the Croatian part of the Adriatic Sea using marine spatial planning (MSP). Initial research to determine the points of interest was conducted based on wind speed. The authors established ten possible points for further research. Subsequently, different parameters were used as inputs for exclusion. The Fuzzy Analytic Hierarchy Process (AHP) method was used to calculate the weighting coefficients for a suitable set of criteria, exactly six of them. Using a combination of geoinformation system (GIS) analysis and weighting coefficients established through Fuzzy AHP, four points were established as suitable for OWF installation in Croatia. Finally, the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) method was used to select the best order for OWF positioning in the eastern part of the Adriatic Sea. To conclude, there are not many options for OWF positioning in Croatia. Furthermore, it is clear that they exist and should be explored further.
The paper describes previous maps of the Diocese of Poreč and Pula and creation of a new map of the Diocese made and published after many changes and long-time research at the Faculty of Geodesy, ...University of Zagreb. The data collection of the general geographic content and the sacral content was the first step for the new map visualization of the Diocese. It also describes different problems for special map contents and observed shortcomings on the previous maps, and how they are solved. The research objective was the creation of the new map of the Diocese based on the collected and verified data, showing the exact borders of the Diocese and current borders of the deaneries with current seats. On the new map (
Main Map
) at a scale of 1:120 000, the parish borders with the seats and names of parishes are depicted for the first time.
This paper explains the extent to which the importance of Marine Cadastre (MC) and Marine Spatial Data Infrastructure (MSDI) is recognized in the context of Marine Spatial Planning (MSP), Blue ...Economy (BE) and Blue Growth (BG), in the scientific community. A bibliometric assessment was performed using bibliometrics methodology. The research shows that MC and MSDI are underrepresented in the scientific literature. To the authors’ knowledge, theoretical, educational and capacity-building foundations are not developed enough in this domain. There are many practical issues in the marine and maritime domain that needed to be solved by the technical and engineering professions. They can be solved based on theoretical, scientific research and practical experience in different countries. The analysis of scientific papers was performed, together with different countries’ contributions, in the scientific database ISI Web of Science Core Collection (WoSCC). Another issue analysed is countries’ collaboration. The results show that there is almost no collaboration in the MC domain and some, but insufficient, in the MSDI domain. Based on analysing the recognition of the MC domain, as a basic layer of MSDI, the results are more satisfying than in other parts of the research.
The accurate detection and treatment of weeds in agricultural fields is a necessary procedure for managing crop yield and avoiding herbicide pollution. With the emergence of unmanned aerial vehicles ...(UAV), the ability to acquire spatial data at the desired spatial and temporal resolution became available, and the resulting input data met high standards for weed management. In this paper, we tested four independent classification algorithms for the creation of weed maps, combining automatic and manual methods, as well as object-based and pixel-based classification approaches, which were used separately on two subsets. Input UAV data were collected using a low-cost RGB camera due to its affordability compared to multispectral cameras. Classification algorithms were based on the random forest machine learning algorithm for weed and bare soil extraction, following an unsupervised classification with the K-means algorithm for further estimation of weeds and bare soil presence in non-weed and non-soil areas. Of the four classification algorithms tested, the automatic object-based classification method achieved the highest classification accuracy, resulting in an overall accuracy of 89.0% for subset A and 87.1% for subset B. Automatic classification methods were robustly developed, using at least 0.25% of the scene size as the training data set in all circumstances anticipated for the random forest classification algorithm to operate. The use of the algorithm resulted in weed maps consisting of zoned classes and covering areas with similar biological properties, making them ready for use as inputs in weed treatments that use agricultural machinery.
The need for the detection and monitoring of changes in the environment is greater today than ever before. Through classification we can obtain insights into the state of the land surface. No known ...classification methods are fully automated, and their implementation requires preprocessing and postprocessing. This research provides a novel, fully automatic and cost-effective land cover classification method (ALCC). This novel automatic method does not require prior knowledge of the terrain or the assignment of training samples. The ALCC method is based on unsupervised classification methods, which is performed over the spectral indices rasters and six Landsat-8 30 m spatial resolution bands. The method was tested in three different study areas. Furthermore, all three study areas were classified by common supervised classification methods, namely, the Maximum Likelihood Classification (MLC) and the Random Forests (RF) method. For comparison accuracy, assessment of the three applied classification methods, namely, the figure of merit, overall agreement, omission and commission, were used. The results show that the overall agreement of the new automatic classification method for the Rijeka, Zagreb and Sarajevo study areas is 90.0%, 89.5% and 89.9%, respectively, and the overall agreement always falls between the overall agreement of the MLC method (88.1%, 88.9% and 86.7%, respectively) and the overall agreement of the RF method of classification (91.7%, 90.4% and 90.2%, respectively). These results confirm that this new automatic, cost-effective and accurate land cover classification method can be easily applied for numerous remote sensing applications.
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•Research purpose a novel, fully Automatic Land Cover Classification method (ALCC).•ALCC does not require prior knowledge of the terrain and training polygons.•Unsupervised ALCC is based on the spectral indices and 6 Landsat-8 (30 m) bands.•ALCC has better accuracy than MLC and slightly lower than RF.•The purposed method is much faster and cost-effective than MLC and RF.
Precizno umjeravanje kalibracijskih baza obavlja se svjetlosnim interferometrima, preciznim elektrooptičkim daljinomjerima i GNSS-om. U radu je dan pregled 14 kalibracijskih baza u 11 država svijeta ...umjerenih s jednom ili više preciznih metoda. Umjereni precizni elektrooptički daljinomjeri standard su za transfer sljedivog mjerila na nove kalibracijske baze. Daljnja umjeravanja na kalibracijskim bazama moguće je provesti neovisnim metodama što omogućuje kontrolu mjernih rezultata. Među prikazanim rezultatima dani su podaci posljednjeg umjeravanja kalibracijske baze Geodetskog fakulteta Sveučilišta u Zagrebu preciznim elektrooptičkim daljinomjerom i GPS-om. Provedena je analiza parametara umjeravanja svih 14 kalibracijskih baza. Kao najvažniji parametar umjeravanja za svaku kalibracijsku bazu iskazana je mjerna nesigurnost najveće umjerene duljine uz odgovarajući faktor proširenja.
U ovom radu je opisana metoda geometrijskog nivelmana s posebnim fokusom na nivelman visoke točnosti i precizne nivelmanske letve. Navedeni su i objašnjeni utjecaji nesavršenosti preciznih ...nivelmanskih letvi na mjerenja u nivelmanu visoke točnosti, kao i metode modeliranja, minimiziranja i eliminacije sustavnih pogrešaka letvi. Također su opisani pojam i proces umjeravanja preciznih nivelmanskih letvi te razvoj metoda i komparatora za umjeravanje s fokusom na komparatore s integriranom CCD kamerom. Pobliže je opisan komparator Laboratorija za mjerenje i mjernu tehniku Geodetskog fakulteta Sveučilišta u Zagrebu, te je prezentiran plan njegova osuvremenjivanja razvojem nove metode umjeravanja geodetskih linearnih mjerila integriranjem CCD kamere.
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