Stereographic projections

Need to project planes and lines

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Orthographic projections (will use in lab a little, less widely applied) Stereographic projection ( a form of spherical projections) - great deal of use in structural geology) -

Imagine planes or lines being projected onto a hemisphere

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Lower hemisphere projection (always look from above) - convention Can use azimuth (200 degrees) or geographic (S20W) with stereonets

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A NS plane

….and its pole

Orientation of a line

Can use to :1plot data and 2 calculate geometries For example: if you have two lines in a plane, one can easily determine the orientation of the plane

Exercises

today

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Plotting a plane Plotting a line Plotting a plane and a line contained in the plane Finding apparent dips Finding true strike and dip from apparent dips Finding the plunge and trend of 2 intersecting planes Determining the dihedral angle between planes

Read: • Text 691-720 - stereonets