Data format. Your data needs four columns: Unit, Plane type, Azimuth, Dip. Azimuth and Dip are in degrees.
Convention. By default, Azimuth = dip direction (the compass bearing in which the plane dips). If your measurements use strike with right-hand rule, switch the convention in the left panel.
Projection. Equal-area (Schmidt), lower hemisphere — the standard for structural geology.
Statistics. Mean vectors use Fisher (1953) statistics on poles. The fold axis (π-pole) is the eigenvector of the smallest eigenvalue of the orientation matrix of all poles — i.e. the best-fit girdle's normal.
Density contours. Kamb (1959) method with 3σ counting circle, contoured at 2σ intervals.
Styling. Each Unit (or Plane type) gets its own color, line/marker size, and symbol — customizable in the right panel.
Export. Choose a resolution (2000 px is good for publication) and pick PNG, JPG, or SVG.
References: Fisher (1953); Kamb (1959); Vollmer (1990); Allmendinger et al. (2012) Structural Geology Algorithms.