The use of network analysis to creating a model of Triangulated Irregular Network (TIN) on the basis of the data from Polish Active Geodetic Network EUPOS (ASG EUPOS) stations

A system of referential stations ASG EUPOS launched in 2008 in Poland provides, among others, information regarding the changes of the stations' vertical and horizontal coordinates. These changes can be related to the changes of tectonic plates. One can create models of the vertical and horizontal movements of the Earth's crust. The changes of height of the referential stations are more difficult to model than horizontal changes. The evaluation of credibility of these changes is also more challenging. The velocities of the vertical changes can be determined in two ways: as absolute velocities (on referential stations) or as relative velocities - between the stations. Although the referential stations are located evenly within the Polish territory, they do not compose preordained geometric shapes. Such an arrangement allows for certain freedom of creating connections of the stations between which the relative vertical movements are determined. Although one popular method of creating the TIN is Delaunay triangulation, there are methods relating to network analyses allowing for connecting the points in another way. The purpose of this article is to employ various analytical methods to create the TIN of the relative vertical movements. The chosen methods of network modelling are characterised and compared. Moreover, their utility regarding the creation of a model of relative vertical movements within Poland's territory is evaluated.