Cartography and Visualization
Cartography and Visualization tests whether your map communicates accurately, not merely whether it renders. Expect symbology and classification choices, labeling, layout composition, scale-dependent display, map series, and 3D scene design.
Symbology and classification
Use unique values for categories, graduated colors or symbols for ranked numeric data, and proportional symbols when magnitude matters more than class. Normalize counts by area or population; otherwise large polygons dominate. Classification methods behave differently: equal interval is easy to read but hides skew; quantile balances counts per class but splits similar values; natural breaks minimizes within-class variance but is hard to compare across maps; standard deviation highlights deviation from the mean; manual breaks preserve a fixed story. Bivariate colors show two variables at once and require a two-dimensional legend.
Labels, layouts, and scenes
Label classes let one layer use different queries, expressions, and symbols. Maplex controls placement, conflict, and priority; annotation is stored geometry and can be edited individually. A layout contains map frames, legends, scale bars, dynamic text, and grids. A map series repeats pages by index layer, bookmark, or page number. In 3D, scenes use elevation surfaces, extrusion, lighting, and vertical exaggeration; line-of-sight and viewshed answer visibility questions.
Worked example
Map county population change. Raw population would emphasize large counties, so use percent change and a diverging color scheme centered on zero. Set manual breaks at -10, -5, 0, 5, and 10 percent. Add a label class that shows only counties with more than 20 percent growth, using a bold halo. Reasoning: percent change is comparable across county sizes; manual breaks make the zero point meaningful; a diverging scheme shows direction; and the label class avoids labeling every county.
Traps
Do not map raw counts when rates are the question. Do not compare natural-breaks maps with different breaks and call them comparable. A definition query removes features from display, while a display filter is a rendering setting; neither edits the data. Scale ranges can hide layers unexpectedly. Check that the legend patch matches the layer symbology and that layout text is not mistaken for a label. Avoid red-green-only schemes where color vision is a concern.