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Wyświetlanie 1-2 z 2
Tytuł:
Analysis of height determination using the ASG-EUPOS NAWGEO service
Autorzy:
Dawidowicz, K.
Powiązania:
https://bibliotekanauki.pl/articles/298453.pdf
Data publikacji:
2013
Wydawca:
Uniwersytet Warmińsko-Mazurski w Olsztynie
Tematy:
ASG-EUPOS
NAWGEO
RTK
GNSS
satellite leveling
geoid
Opis:
GNSS observations carried out in a network of permanent stations are a complex systems which offer post-processing as well as corrections sent in real-time and the creation of so-called virtual observations. Currently, there are several Network-based Real Time Kinematic (NRTK) services around the world. In Poland, such a system has been in operation since June 2008, known as the Polish Active Geodetic Network (ASG-EUPOS). Three real-time correction services and two postprocessing services are currently used by users. NRTK technique uses GNSS observations gathered from a network of Continuously Operating Reference Stations (CORS) in order to generate more reliable error models that can mitigate the distance dependent errors within the area covered by the CORS. This method has been developed and tested considerably by many scientists during recent years. These studies have demonstrated the high centimeter accuracy that can be achieved using NRTK technique. This study analyzed the accuracy of the height determination with NRTK measurements using ASG-EUPOS. The results obtained show that RTK ASG-EUPOS height measurements are characterized by high precision, but the normal height measurements compared to the height measurements obtained from precise leveling, probably due to some systematic errors (the mean of many measurements differs significantly from the actual value) are not so accurate. In this case, fitting NRTK results to a precise leveling network may significantly improve the results. In presented test this resulted in reducing NRTK normal height determination errors by 70 percent.
Źródło:
Technical Sciences / University of Warmia and Mazury in Olsztyn; 2013, 16(1); 19-39
1505-4675
2083-4527
Pojawia się w:
Technical Sciences / University of Warmia and Mazury in Olsztyn
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Estimation of covariance parameters for GNSS/leveling geoid data by Leave-One-Out validation
Autorzy:
Jarmołowski, W.
Powiązania:
https://bibliotekanauki.pl/articles/298144.pdf
Data publikacji:
2013
Wydawca:
Uniwersytet Warmińsko-Mazurski w Olsztynie
Tematy:
GNSS
leveling
geoid
least squares collocation
leave-one-out
LOO
covariance
noise
Opis:
The article describes the estimation of covariance parameters in Least Squares Collocation (LSC) by Leave-One-Out (LOO) validation, which is often considered as a kind of cross validation (CV). Two examples of GNSS/leveling (GNSS/lev) geoid data, characterized by different area extent and resolution are applied in the numerical test. A special attention is focused on the noise, which is not correlated in this case. The noise variance is set to be homogeneous for all points. Two parameters in three covariance models are analyzed via LOO, together with a priori noise standard deviation, which is a third parameter. The LOO validation finds individual parameters for different applied functions i.e. different correlation lengths and a priori noise standard deviations. Diverse standard deviations of a priori noise found for individual datasets illustrate a relevance of applying LOO in LSC. Two examples of data representing different spatial resolutions require individual noise covariance matrices to obtain optimal LSC results in terms of RMS in LOO validation. The computation of appropriate a priori noise variance is however difficult via typical covariance function fitting, especially in the case of sparse GNSS/leveling geoid data. Therefore LOO validation may be helpful in describing how the a priori noise parameter may affect LSC result and a posteriori error.
Źródło:
Technical Sciences / University of Warmia and Mazury in Olsztyn; 2013, 16(4); 291-307
1505-4675
2083-4527
Pojawia się w:
Technical Sciences / University of Warmia and Mazury in Olsztyn
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-2 z 2

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