[stereonet-equal-area] Structural Geology Stereonet (Equal-Area Projection)

[MarkusNeusinger]

Description

A Schmidt equal-area (or Wulff equal-angle) stereographic projection plotting geological structural data such as bedding planes, faults, joints, and lineations as great circles and poles on a lower-hemisphere projection.

Key Visual Elements

• Circular plot with primitive circle
• Great circles representing planes (strike/dip)
• Poles to planes as points
• Rose diagram overlay for strike directions (optional)
• Density contours for clustered data (Kamb or 1% method)
• North arrow and degree markings

Applications

• Structural geology: analyzing fault and fracture orientations
• Mining geology: rock mass characterization
• Geotechnical engineering: slope stability analysis (kinematic analysis)
• Tectonics research: stress field determination

Domain

Geology / Earth Sciences

[claude]

✅ Spec ID: stereonet-equal-area

Rationale: Stereonet is a distinct specialized plot type not yet in the catalog; the equal-area variant specifies the Schmidt (lower-hemisphere) projection which is the standard for structural geology analysis.

No duplicates found. Related but different specs exist (polar-basic, rose-basic, ternary-basic) — none covers stereographic projection of geological structural data.

[github-actions]

✅ Specification Ready: stereonet-equal-area

PR: #4604

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specification.md

stereonet-equal-area: Structural Geology Stereonet (Equal-Area Projection)

Description

A Schmidt equal-area (lower-hemisphere) stereographic projection for plotting geological structural data. Great circles represent planar features (bedding, faults, joints) by their strike and dip, while poles to planes are plotted as points showing the orientation of the normal to each plane. Density contours highlight preferred orientations in clustered data. This is the standard projection used in structural geology for analyzing fabric elements and kinematic indicators.

Applications

• Structural geology: mapping and analyzing fault, fracture, and bedding orientations from field measurements
• Geotechnical engineering: kinematic analysis for slope stability assessment using discontinuity orientations
• Mining geology: rock mass characterization by visualizing joint set distributions and their spatial relationships

Data

• strike (numeric, degrees 0-360) - azimuth of the line of intersection between the plane and a horizontal surface
• dip (numeric, degrees 0-90) - angle of maximum inclination of the plane from horizontal
• dip_direction (numeric, degrees 0-360) - azimuth of the dip direction (alternative to strike, offset by 90 degrees)
• feature_type (categorical) - classification of the measurement (e.g., bedding, fault, joint, foliation)
• Size: 30-200 measurements typical for a single stereonet
• Example: field measurements of bedding planes and joint sets from a geological mapping campaign

Notes

• Use lower-hemisphere equal-area (Schmidt net) projection; this preserves area relationships making density analysis meaningful
• Great circles should be drawn for planes; poles (points) plotted at 90 degrees to each plane
• The primitive circle represents the horizontal plane; North is at top (0/360 degrees)
• Include degree tick marks every 10 degrees around the perimeter and a North arrow or "N" label
• Color-code features by feature_type with a legend
• Overlay Kamb density contours on pole data to highlight preferred orientations
• Grid lines (equal-area net grid) should be subtle (light gray, thin lines) to avoid visual clutter

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Next: Add approved label to merge this specification to main.

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🤖 spec-create workflow

[github-actions]

🚀 Specification Merged!

Specification: stereonet-equal-area
PR: #4604 (merged)

The specification is now in main and synced to PostgreSQL.

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Next: Add generate:{library} labels to start generating implementations.

Available libraries: matplotlib, seaborn, plotly, bokeh, altair, plotnine, pygal, highcharts, letsplot

Or use workflow dispatch for bulk operations.

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🤖 spec-create workflow