Spherical Projections

Frederick W. Vollmer, SUNY New Paltz

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Initial Publication Date: June 1, 2012 | Reviewed: January 19, 2015 (see revision history: 2 events)

Summary

This is a sequence of two labs on spherical projections and orientation data analysis. The first lab in the semester introduces data formats for lines and planes (strike, dip, trend, plunge, etc.). Spherical geometry is emphasized and projections and terms are defined. Students solve basic problems using Schmidt nets. The second lab, later in the semester, uses the computer program Orient to examine properties of projections and learn advanced concepts such as eigenvectors, data rotation, contouring, and importing of graphs to Adobe Illustrator, LibreOffice, MS Word, and other programs for presentation.

Structural Visualizations, Folds/Faults/Ductile Shear Zones, ...(more) | College Upper (15-16)

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Context

Audience

Undergraduate geology major junior or senior level structural geology laboratory.

Skills and concepts that students must have mastered

None required, however ideally builds on conceptual skills developed in physical geology, mineralogy, and stratigraphy. A previous introduction to strike and dip in the field or another course is helpful, but not assumed.

How the activity is situated in the course

This is a sequence of two labs. The first is the first in the semester and introduces lines and planes as data. The second is later in the semester, after they have done problem solving by hand, to give them computer skills and advanced techniques. This is a good introduction for students who will do field-based research projects, and will need to analyze and present their data.

Goals

Content/concepts goals for this activity

Spherical projections, orientation data analysis, equal-area projections, Schmidt net (stereonets are not used).

Higher order thinking skills goals for this activity

Conceptualization of three dimensional data, descriptive statistical analysis, critical evaluation of terminology use.

Other skills goals for this activity

Computer skills, downloading and installing software from web, importing diagrams into Adobe Illustrator, LibreOffice, etc., for presentation.

Description and Teaching Materials

Spherical Projection Labs (Acrobat (PDF) 555kB May14 12)

Teaching Notes and Tips

The instructor will need to introduce the angular measures of lines and planes, strike (with right hand rule), dip, trend and plunge are sufficient. Note that the labs use Schmidt nets, no stereonets are used. When discussing terminology I encourage the students to search for errors in published materials, including journal articles and textbooks, they are easy to find (have them do a web search on "equal-area stereographic projection", which is a contradiction).

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Assessment

I grade the labs, but do not rely heavily on that. They will need the material in subsequent work to succeed. A final lab practical exam checks basic skills.