A Novel Robust Scaling for EDM Calibration Baselines using Monte Carlo Study

The terrestrial measurements using Electronic Distance Measurement (EDM) have been widely done for different applications such as deformation monitoring and establishing geodetic networks. The calibration of the EDMs reflects the quality of the estimated parameters. In geodesy, least squares principle is mainly used for estimating parameters. The least square estimation is adversely affected by the systematic and non-systematic errors resulting in bias for the estimated parameters. In this study, to compare efficacy of different robust methods, the Monte Carlo simulation is applied to the EDM calibration as well as real experiments. The parameters without errors are obtained as a result of the used methodology. The methods given in this study are basically based on iteratively reweighted least squares and can be used for both parameter estimation and outlier diagnostics. This is of particular importance for calibrations of electromagnetic distance measurements using the Monte Carlo simulation and the measured test baselines. The results showed that one of the advantages of the used methodology is the improvement of the reliability of the estimated calibration parameters

Accuracy Assessment of Low Cost UAV Based City Modelling for Urban Planning

This paper presents an Unmanned Aerial Vehicles (UAV) based 3D city modelling approach to be used in managing and planning urban areas. While the urban growth is rapidly increasing in many places of the world, the conventional techniques do not respond to the changing environment simultaneously. For effective planning, high-resolution remote sensing is a tool for the production of 3D digital city models. In this study, it is aimed at designing the remote sensing by UAV through urban terrain. Using all the information produced from UAV imagery, high-accurate 3D city models are obtained. The analysis of XYZ data of the derived from 3D model using UAV photogrammetry revealed similar products as the terrestrial surveys which are commonly used for the last development plans and city maps. The experimental results show the effectiveness of the UAV-based 3D city modelling. The assessed accuracy of the UAV photogrammetry proved that urban planners can use it as the main tool of data collection for boundary mapping, changes monitoring and topographical surveying instead of GPS/GNSS surveying

A new approach to outlying data in estimation of vertical total electron content

U svim vrstama znanstvenih studija, za obradu analitičkih podataka pitanje outliera je od bitne važnosti. Na točnost Total Electron Content (TEC) modela koja se postiže na temelju podataka Sustava za Globalno Pozicioniranje (GPS) sa zemlje uvelike djeluju čimbenici kao što su geometrija satelita, kut prekida, visina ionosferske ljuske, količina GPS podataka i sl. Vjerojatni outlieri među promatranima imaju značajan učinak na kvalitetu procijenjenog TEC modeliranja. Njih je potrebno ukloniti iz TEC vremenskih serija kako bi se dobili pouzdaniji rezultati za daljnji postupak. Iako su neke analitičke metode razvijene za code-outliers, phase-slips i poremećaje u ionosferi, značajno smanjenje broja mjerenja negativno bi moglo utjecati na kvalitetu nastalih TEC vrijednosti primjenom njihovih kombinacija bez geometrije. U ovom istraživanju, predložili smo novi pristup za otkrivanje outliera koji će se koristiti u kombinacijama bez geometrije u procjeni vertikalnog TEC-a bez smanjenja broja promatrača koda. Ovdje se GPS podaci dobiveni iz 22 stalnih postaja koriste za procjenu VTEC-a na dan 14-15 svibnja 2005. Rezultati istraživanja dobiveni detaljnom obradom jasno pokazuju učinkovitost metode. Naše istraživanje pokazuje da se predloženi pristup pokazao kao brza, učinkovita i objektivna metoda za otkrivanje učinaka outliersa koji dovode do nepravilnog modeliranja. Osim toga, VTEC mape dobivene novim pristupom pouzdano se razlikuju u odnosu na podatke, uključujući vanjske promatrače (outlying observables). Slijedom toga, predloženi postupak može biti alternativa odbacivanju outliera u procjeni VTEC-a, u kojoj su vanjska (outlying) zapažanja zadržana u kombinacijama bez geometrije.For all scientific studies, for processing analytical data the subject of outliers is of critical importance. The accuracy of Total Electron Content (TEC) models obtained from ground based Global Positioning Systems (GPS) data is strongly affected by some factors such as satellite geometry, cut-off angle, ionospheric shell height, quantity of GPS data etc. Probable outliers within the observables have a significant effect on the quality of the estimated TEC modelling. These should be removed from the TEC time series in order to get more reliable results for further process. Although some analytical methods have been developed for the code-outliers, phase-slips and ionosphere disturbances, significant reduction in the number of measurement could adversely affect the quality of the generated TEC values using geometry-free combinations of those. In this study, we proposed a novel approach for outlier detection to be used at geometry-free combinations in estimation of vertical TEC without reducing the number of code observables. Here the GPS data obtained from 22 permanent stations are used to estimate the VTEC on May 14-15, 2005. The research results from the detailed processing clearly show the efficiency of the method. Our research shows that the proposed approach appears to be a fast, effective and objective method to detect outlying effects which cause improper modelling. Moreover the resulting VTEC maps from the new approach differ reliably with respect to the data including outlying observables. Consequently, the proposed method could provide an alternative to outlier rejection in estimation of VTEC, in which outlying observations are retained in geometry-free combinations