## 5 Discussion  
We can summarize the results for visualizing temperature on geographic maps as follows. Sequential color schemes significantly outperformed other schemes in user reading of temperature values. Qualitative color schemes are significantly inferior to the other color schemes, with the worst combination being the qualitative scheme with nine colors. Further examination of the color schemes in the best performing group, the sequential group, revealed no significantly better color scheme among the two observed (YLOrRd/Reds). It also appears that the user's reading accuracy is not related to the number of colors used in the color schemes (3/6/9) nor to the order of the colors on the respective maps (ascending/descending). The results are consistent with related studies showing that sequential color schemes best represent sequential data [56; 57].  
In this discussion, we also consider the method performed and suggest improvements for future UCD-based geovisualization studies. The number of participants in the study and their level of expertise (novice) are consistent with the guidelines for usability testing in quantitative studies [18]. The methodology performed is in line with related evaluation studies in the field of geoinformation services [58]. In data analysis, the rank-based ANOVA statistics are applied as an alternative to parametric ANOVA. The theoretical and simulation results prove the high accuracy of the method [59; 60].  
However, the method has some design and procedural limitations that need to be addressed here. Considering the instruments used in the study, it is noticeable that sequential color schemes are used more frequently than qualitative and diverging color schemes. Color schemes were selected based on recommendations for ordered data [31] and with the intention of covering both multi-hued and single-hued color schemes. However, because we used a relatively small number of questions (the reasons for this are explained in Section 3.2), the data available for further analysis seem to cover only a relatively small number of maps in terms of color schemes (Procedure 2) and the order of colors in sequential maps (Procedure 3), as shown in respective descriptive statistics reports (Tables 11 and 13). This limitation could be overcome by increasing the number of questions while attempting to keep participants' cognitive fatigue low and the reliability of their readings high.  
Furthermore, Procedures 2 and 3 are performed on the maps with nine colors, which scored significantly lower than maps with three and six colors in the Procedure 1 (although equal to other numbers of colors when considered in interaction with the color schemes, as shown in Table 9). This can also be considered as a limitation of the study. The questionnaire was designed before the study was conducted, and we had no opportunity to obtain additional data. For future studies, we may recommend a different study design in which the questionnaire could be constructed in multiple phases, with questions in subsequent phases building on the results of the previous phases. Such a design would require a much larger number of participants, as a new sample would be needed for each phase. In addition to sample size, future studies should also consider a larger pool of geovisualization users to ensure randomization of age and gender in the sample. Both requirements could be met by crowdsourcing rather than convenience sampling.