Evaluating Adequacy and Usability of Soil Maps in Croatia

The paper suggests a methodological framework for evaluating adequacy and usability of soil maps by analyzing the following 10 aspects: lineage, consistency, completeness, effective scale, attribute accuracy, thematic contrast, accuracy of legends, integrity, popularity, and accessibility. This framework was used to evaluate the national soil resource inventory in Croatia and to find out why the maps are not used to the full potential. Six 1:50K map sheets (of 185 in total), 3 control surveys, and 10 full profile descriptions in the main landscape regions of Croatia were used to estimate the effective map scale and thematic accuracy of profile observations. In addition, the existing digital data sets (digital soil map and database with 2198 profiles) were evaluated for thematic purity and contrast. The results show that the soil maps are of lower quality than planned and that their usability for spatial planning is limited. The average polygon size and the positional accuracy of primary soil boundaries correspond to the 1:150K scale, while the intensity of field observations corresponds to the 1:250K scale. Mapping units are heterogeneous for mapping of clay content, pH, and organic matter, with an average normalized variation of 68% within units and the mean thematic overlap of 66% between geographically adjacent units. This makes this inventory adequate for small-scale applications only. The major usability problems identified were lack of specific interpretations corresponding to user needs, unpopularity of soil survey concepts, inconsistency of methodology and unclear distribution policy. The evaluation can be used to decide how to improve the usability of the existing datasets and design methodological steps for a new survey by involving end users in the design of the soil information system.