Assessment of the quality of colour scales: a case study "Landscape Atlas of Czech Republic"

Abstract. The atlas, as a typical product of thematic cartography, is characterized by cohesive approaches in the procedures of atlas compilation. One of the results of these cohesive approaches is the uniform setting of colour scales in choropleth maps. The paper aims to evaluate the quality of colour scales in choropleth maps in an atlas from the point of view of systematic visualization, using the example of the electronic version of the Landscape Atlas of the Czech Republic. A total of 56 sequential and 6 divergent colour scales were selected from the Atlas. Seven hypotheses related to colours were formulated and then tested. The paper assumes that the colour scales in the atlas are not uniformly constructed. The authors hypothesise the approach by which the creators of the atlas chose these colours. In the CIELAB colour model, the colour distances between the colours of the intervals were measured, calculated, statistically evaluated and graphically expressed. The colour scales were also evaluated against the background of the map sheets. The results revealed the nature of the approach of the authors of the Atlas when compiling colour scales of choropleth maps. The aim of the paper was also to define the criteria for evaluating the quality of colour scales and to formulate recommendations for the compilation of colour scales. These recommendations should help map makers to create high-quality atlas maps and users to get more accurate and faster information from maps.