| Summary: | The main attention in the present study was focussed on quantitative observations of the influence that centres have on their surroundings. The relative area of influence of Forssa, which is situated in south‑western Häme, was selected as the empirical experimental area of the gravitational models. Gravitation was measured by the frequency of visits made to the centres, and the distance variable in the gravitational models was road‑distance. The linear model of the Pareto‑type as well as the square model were employed as functions expressing field force. In central class III, the square model appeared to adjust itself better to empirical changes in field force than the linear model, while in the lower class of centrality, class II, the models were approximately equal. As a whole, the differences in the explanatory degree of the models were so slight that the linear model could be interpreted as a reliable and, due to its simplicity, a very useful function to express field force. The decline in gravitation was studied in detail with the help of 4 profiles of field force as well as linear graphs calculated by sectors.
The areal distribution of field force was illustrated by isarithmic maps. For their preparation the values of field force were computed by areal units with the aid of the filtering method, which was further improved by weighing coefficients. The general applicability of the method has already been verified in the treatment of data of visiting frequencies covering the whole country.
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