engleski

Extension of the Croatian fundamental gravity network to the north Adriatic islands

In September and November 2007 Croatian Fundamental gravity network (FGN) has been extended to north Adriatic islands by relative gravimetry. The paper describes FGN extension measurements, applied adjustment models and analyses of results with critical remarks. In order to ensure homogeneity of the network, the extension has been designed in accordance with initial FGN, apart from station separation and mean of transportation. The extension has been adjusted according to the least squares principle, first as independent free network, subsequently as biased network with stations from present FGN fixed. Two adjustment models have been applied for both datum definitions. For one model of adjustment daily drift corrections have been determined prior to adjustment, while in second introduced as parameters in functional model. For both models of adjustment, stochastic model is based on variances of gravity readings but involves total mathematical correlation and estimated uncertainty of daily drift corrections (if determined prior to adjustment). Although drift values differs significantly, estimated gravity values from two models show no significant difference (up to 0.008 μ ms-2). Standard deviations of estimated gravity values for model 1 and 2 do not exceed 0.08 μ ms-2 and 0.09 μ ms-2, respectively. All computations have been preformed automatically by several programming functions developed in Matlab. Since within next 2 years FGN extension to all significant Adriatic islands is planned, described extension procedure is only a first phase that shall provide valuable experience in forthcoming projects.

network; relative gravimetry; adjustment models

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