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## Stereographic projections

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**Need to project planes and lines**• 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**• Lower hemisphere projection (always look from above) - convention • Can use azimuth (200 degrees) or geographic (S20W) with stereonets**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**Exercisestoday**• 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 • 34-35 The San Manuel fault