Charts that display location-based values by coloring geographic units on an actual map are called choropleth maps. If the goal is to show the level of a single parameter, an appropriate color should be selected and a legend created using a gradient from its lightest to darkest tones. If the map is meant to communicate positive and negative situations, the color scale should be centered around a neutral tone with diverging shades for positive and negative values. One limitation is that larger land areas can visually dominate the map, potentially leading to misinterpretation of the data during visual evaluation.