Δημιουργία τοπικού μοντέλου γεωειδούς στη περιοχή της Θεσσαλίας

Διαμαντής, Ιωάννης; Diamantis, Ioannis

dc.contributor.author	Διαμαντής, Ιωάννης	el
dc.contributor.author	Diamantis, Ioannis	en
dc.date.accessioned	2016-04-20T09:52:55Z
dc.date.available	2016-04-20T09:52:55Z
dc.date.issued	2016-04-20
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/42418
dc.identifier.uri	http://dx.doi.org/10.26240/heal.ntua.10464
dc.rights	Default License
dc.subject	Γεωειδές	el
dc.subject	Μέθοδοι χωρικής παρεμβολής	el
dc.subject	Τελλουροειδές	el
dc.subject	Ανωμαλίες ελευθέρου αέρα	el
dc.subject	Αναγωγές βαρύτητας	el
dc.subject	Γεωδαιτικοί μετασχηματισμοί	el
dc.subject	Συνοριακά προβλήματα	el
dc.title	Δημιουργία τοπικού μοντέλου γεωειδούς στη περιοχή της Θεσσαλίας	el
heal.type	bachelorThesis
heal.classification	Δορυφορική γεωδαισία	el
heal.language	el
heal.access	free
heal.recordProvider	ntua	el
heal.publicationDate	2015-10-09
heal.abstract	Αντικείμενο αυτής της εργασίας είναι η μελέτη προσδιορισμού ορθομετρικών υψόμετρων με τη βοήθεια μετρήσεων GPS, γεωμετρικής χωροστάθμησης και τη χρήση τοπικών μοντέλων του γεωειδούς. Τα τοπικά μοντέλα του γεωειδούς υπολογίζονται με τη βοήθεια συγχρόνων τεχνικών προσδιορισμού ,μέσα από διαδικασία αφαίρεσης και επαναφοράς (remove-restore techniques) των συνιστωσών του πεδίου βαρύτητας. Οι σύγχρονες τεχνικές, που εφαρμόζονται και συγκρίνονται, θεωρούνται οι αντιπροσωπευτικότερες για τον ακριβή και ταχύ προσδιορισμό τοπικών μοντέλων επιφανειών γεωειδούς. Χρησιμοποιείται η πλέον ακριβής διαδικασία των μετασχηματισμών Fourier, ο μονοδιάστατος (1-D) σφαιρικός ταχύς μετασχηματισμός. Ο προσδιορισμός των υψόμετρων διαχωρίζεται ουσιαστικά σε δυο τμήματα: στο τμήμα που αφορά στις μετρήσεις GPS και γεωμετρικής χωροστάθμησης, και στο τμήμα που αναφέρεται στο προσδιορισμό μοντέλων της επιφάνειας του γεωειδούς. Ο τελικός στόχος της μελέτης είναι η βελτίωση στη ακρίβεια προσδιορισμού ορθομετρικών υψόμετρων με τη χρήση σύγχρονων τεχνολογιών και μια πρώτη προσπάθεια εφαρμογής των παρουσιαζομένων μεθοδολογιών στον ελλαδικό χώρο. The main goal of this thesis is the local/regional precise orthometric height determination by combining GPS and gravity measurements and taking advantage of local geoid models. The local geoid models are computed by using the efficient Fast Fourier Transform (FFT) techniques, based on the remove-restore methodology which is widely used in applications of physical geodesy. Different ways for the improvement of orthometric height determination in a limited test area, using all the available heterogeneous data sources and the most reliable current approaches, are also discussed. Numerical tests are carried out and important conclusions are drawn with respect to the results and the accuracies achieved.	el
heal.abstract	The main goal of this thesis is the local/regional precise orthometric height determination by combining GPS and gravity measurements and taking advantage of local geoid models. The local geoid models are computed by using the efficient Fast Fourier Transform (FFT) techniques, based on the remove-restore methodology which is widely used in applications of physical geodesy. Different ways for the improvement of orthometric height determination in a limited test area, using all the available heterogeneous data sources and the most reliable current approaches, are also discussed. Numerical tests are carried out and important conclusions are drawn with respect to the results and the accuracies achieved. The determination of geoid is a subject that occupies a lot the last years the world scientific community. With the growth of Global Positioning System (GPS), with which we can take with satisfactory precision geometric heights is necessary the determination of precise geoid for their transformation directly in orthometric heights. Moreover exist applications in other scientific fields as geophysics and seismology which are facilitated with the existence of precise geoid. Particularly important stage before any one calculation is the preparation of measurements and their exemption from systematic faults. Moreover is particularly important, the equitable choice of method and reductions that we will use, in order that they are reported in a concrete surface of report. Thus, depending on the way that we reduce the measurements and the surface of report that we use, remains a quantity of indirect effect in the geoid which also it should him we remove from the final calculations. As better method of reduction of topographic masses near the station was judged the reduction of remaining topographic model (RTM). For the calculation of geoid have been developed different ways of determination which provide different results for each data set. The procedure remove-restore is used in every of these methods. Also it is used with various variants (transformation Fourier 1D or 2D, level or overall approach, numerical completion) the integral of Stokes, but also the specific adaptation in total of constant points which can become in a total of initial measurements or even in a later stage at the adaptation of gravimetric geoid in measurements of abstention of geoid with GPS. In a short review in the methods of determination of geoid that are published in the internet is shown the diversity of methods that is used in each region and in each different data set. Also it becomes explicit that does not exist a most optimal method of determination of geoid that can be applied in each region and with every data set. The software that was used is the Gravsoft which is constituted by a line of programs Fortran which is essentially for the successive calculations. It can support almost all the known methods of determination of geoid, which becomes with the creation of successive files txt, where the exported file from a tool, becomes imported in next. The software is particularly widespread, and most studies use it on the calculation of geoid. For the determination of geoid in the department of Greece that was selected were used land measurements of gravity, with simultaneous measurements GPS in points of known altitude, what were granted by the HMGS. As world geodynamic model was used EGM 2008 complete in degree and order. The initial measurements of absolute gravity were changed in anomalies of free air using them more recent types of corrections. As topographic reduction were used reductions RTM. The final almost geoid resulted from the integral of Stokes with planar Fourier transformation and was changed in geoid with the utilization of Bouguer anomalies of region. In next stage became the specific adaptation of geoid in the measured points with GPS, using a four parameter transformation. All the process of calculations became with tools of computational Gravsoft. The results of calculation are satisfactorily particular afterwards the adaptation with least square collocation of surface that was determined in GPS points. The medium formal fault of determination for this data is under 2 cm, make that allows the use of model for usual topographic works.	en
heal.advisorName	Παραδείσης, Δημήτριος	el
heal.committeeMemberName	Σταθάς, Δημοσθένης	el
heal.committeeMemberName	Μήλας, Παρασκευάς	el
heal.academicPublisher	Εθνικό Μετσόβιο Πολυτεχνείο. Σχολή Αγρονόμων και Τοπογράφων Μηχανικών. Τομέας Τοπογραφίας. Εργαστήριο Ανώτερης Γεωδαισίας	el
heal.academicPublisherID	ntua
heal.numberOfPages	114 σ.	el
heal.fullTextAvailability	true