Circular plots for two dimensional orientation data include scatter plots, vector mean display, and circular histograms. Circular plots can also be used to display the horizontal angles of lines and planes, such as lineation trends. Note that for planes the dip direction is plotted, the plot can be rotated 90° to display them as strikes if desired. The data may be displayed as directed or undirected. Undirected data plots two points at 180°. The settings for circular plots are located in the Circular Plot dialog box.
A simple circular scatter plot shows the data distribution on the perimeter of a unit circle. Lines may be drawn from the circle center if desired. The vector mean, for directed or undirected data, can also be displayed.
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Two dimensional orientation data is commonly displayed as a circular histogram, where the data count is tallied for bins of a set angular width. The most common type is a rose diagram as shown below left. Unfortunately, a rose standard diagram is biased because the area displayed for a single count increases with the radius. An alternative, therefore, is an equal-area rose where each count has an equal area, show at right.
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A kite diagram, shown below, is another option for displaying the same information. In a kite diagram the bin centers are connected.
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