Basic unit size in the analysis of the distribution of spatial landscape elements on the basis of the lithostratigraphic geodiversity of the Ojców National Park (Poland)

Spatial analyses of landscape element diversity are always carried out on the basis of a previously established analytical grid. It divides the research area into 'n' smaller areas - basic units before calculating various landscape measures for each of them. The selection of an appropriate analytical grid, particularly its cell size, is a key issue for the results obtained and conclusions drawn from them. The article describes the procedure of empirical selection of a basic unit size in the medium-scale landscape and geodiversity analyses employing a regular analytical grid with square cells. The established methodology was based on observations of the distribution of the number of studied feature categories in the analytical grid fields. The correctness measures for the selection of the optimal basic unit size were the distributions themselves, as well as selected descriptive statistical parameters. The conducted analyses accurately illustrate the dependences between the variable size of the basic unit size and the number of the studied feature categories. The research conducted proves that the simple empirical approximation of the optimal basic unit size is possible. The proposed procedure allowed the determination of the optimal basic unit size for the variation of the lithostratigraphic units of the Ojców National Park. The optimal unit size for the accuracy data typical for a reference scale 1:50 000 was specified as 500 m.