Less Common Techniques — Pie Charts, Dispersion Diagrams, Kite Diagrams, and EQS Radar

📐 Less Common Techniques — Pie Charts, Dispersion Diagrams, Kite Diagrams, and EQS Radar

Pie Charts and Proportional Circles

A pie chart shows how a total is divided into parts. Each segment's angle is calculated as: (value / total) × 360°. The first segment starts at the 12 o'clock position and segments are added clockwise. Pie charts work well for showing proportions at a single location or point in time, but become very difficult to read when there are more than 5-6 slices or when slices are very similar in size.

When NOT to use a pie chart: do not use a pie chart to show change over time (line graph is better); do not use multiple pie charts of the same size to compare totals at different sites (the reader cannot tell which total is bigger). Proportional circles solve this problem: each circle's area (not radius) is made proportional to the total, so you can compare both the total size and the internal proportions across sites simultaneously.

Dispersion Diagrams

A dispersion diagram plots every individual data value as a dot on a vertical scale, grouped by location or category. Unlike a bar chart (which only shows a mean or total), a dispersion diagram reveals how spread out the data is — are all values clustered closely together, or widely scattered? You can add a median line and inter-quartile range to make the comparison of spread more explicit.

Dispersion diagrams are particularly useful in fieldwork when you want to compare the consistency of measurements at different sites — not just the average. Two sites might have the same mean velocity but very different spreads (one highly variable, one consistent). A bar chart would show them as equal; a dispersion diagram would reveal the difference.

Kite Diagrams

A kite diagram is used almost exclusively for transect data, most commonly in sand dune or vegetation succession studies. The x-axis shows distance along the transect; the y-axis is symmetrical above and below a central line. The width of the "kite" at each measurement point represents the abundance, frequency, or cover of a species at that location. Multiple species can be shown on the same diagram, stacked vertically, allowing you to see how different species replace each other along the transect — the process of succession.

Environmental Quality Survey (EQS) Radar / Spider Diagrams

When you have measured multiple separate variables at multiple sites (the typical output of an Environmental Quality Survey — noise, litter, building condition, traffic, greenery, etc.), a radar diagram (also called a spider diagram) allows you to compare all variables simultaneously. Each axis of the polygon represents one variable; the polygon for each site is drawn by plotting the score for each variable and connecting the points. Overlapping polygons for different sites immediately reveal which site scores better across which dimensions.