Milan Rezo

CROATIAN GEOMAGNETIC REPEAT STATIONS NETWORK

Prikazana je uspostava mreže primarnih sekularnih geomagnetskih tocaka na teritoriju Republike Hrvatske. Tocke za istraživanje sekularne varijacije projektirane su sukladno preporukama Coordination Committee for Common European Repeat Station Surveys, kriterijima International Association of Geomagnetism and Aeronomy – IAGA te iskustvima europskih zemalja. Konacne lokacije sekularnih tocaka izabrane su evaluacijom kriterija na samom terenu. U tu svrhu razvijene su i testirane metode određivanja gradijenata totalnog intenziteta ukljucujuci potrebnu programsku podrsku. Iz ispitivanja razlicitih materijala uslijedio je izbor kamene stabilizacije. Tocke mreže stabilizirane su ukopavanjem stabilizacije standardnim geodetskim postupcima. Status svake tocke mreže dokumentiran je obrascima Položajnog opisa i Geomagnetskih parametara.

Methods of Modelling the Distortion Caused by Different Amount and Orientation of Coordinate Corrections between Two Coordinate Systems at Various Locations

The paper explains the ways of modelling a distortion as a phenomenon caused by different amount and orientation of the residuals-coordinate corrections between initial and target coordinate system at different locations and using the lattice grid models. In order to show more clearly the topographic terrain modelling, the application of triangular meshes i.e. TIN models is explained. The paper describes the collocation by least squares method that takes into account the impact of the distortions of neighbouring points in the observation point depending on the distance from the observation point. To model the final distortion computed by least squares collocation as smoothly as possible, the input values of distortion (positional and/or altitude residuals remaining after calculating transformation parameters) the concept of moving average is described, as well as the covariance function that is used to describe the influence of spatial distortion as function of distance. Using Briggs algorithm throughout GRID, the difference between two types of nodes is explained those that have perceived the distortion in their neighbourhood and those without close observation. Further, the deficiency of Briggss method is processed that is primarily intended for highly polished so-called potential models. At the end, the formula for assessing the accuracy of the transformation GRID model is given.