1. Stereographic projections

2. 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) -

3. 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

5. A NS plane

6. ….and its pole

7. Orientation of a line

8. 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

10. Exercises today 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

11. Read: Text 691-720 - stereonets