A contiguous area cartogram is a geographic map in which the area of each region is proportional to numerical data (e.g., population size) while keeping neighboring regions connected. In this study, we investigated whether value-to-area legends (square symbols next to the values represented by the squares' areas) and grid lines aid map readers in making better area judgments. We conducted an experiment to determine the accuracy, speed, and confidence with which readers infer numerical data values for the mapped regions. We found that, when only informed about the total numerical value represented by the whole cartogram without any legend, the distribution of estimates for individual regions was centered near the true value with substantial spread. Legends with grid lines significantly reduced the spread but led to a tendency to underestimate the values. Comparing differences between regions or between cartograms revealed that legends and grid lines slowed the estimation without improving accuracy. However, participants were more likely to complete the tasks when legends and grid lines were present, particularly when the area units represented by these features could be interactively selected. We recommend considering the cartogram's use case and purpose before deciding whether to include grid lines or an interactive legend.

翻译：连续区域变形地图是一种地理地图，其中每个区域的面积与数值数据（如人口规模）成比例，同时保持相邻区域相连。在本研究中，我们探讨了面积极值图例（展示数值及其对应正方形面积的符号）和网格线是否有助于地图读者更准确地判断面积。我们通过实验测定读者推断地图区域数值数据的准确度、速度和置信度。研究发现，当仅告知读者整个变形地图所代表的总体数值而无任何图例时，各区域的估计值分布以真实值为中心但离散度较大。带网格线的图例显著降低了离散度，但导致低估数值的倾向。比较区域间或变形地图间的差异表明，图例和网格线降低了估计速度而无益于提高准确度。然而，当存在图例和网格线时，参与者更倾向于完成任务，特别是当这些特征所代表的面积单位可交互选择时。我们建议在决定是否包含网格线或交互式图例时，应充分考虑变形地图的具体用途和目的。