The stereo net is a 2D representation of a 3D phenomenon. There will be a reduction in data dimensionality when using it; planes plot as great circles, and lines plot at ponts.

This shows a lower hemisphere stereonet with a
plane in red, which plots as a great circle.
The grid is shown in gray, for the polar aspect,
with 10° spacing.
The great circle does not follow any of the
lines on the gray grid. The strike is where the great
circle intersects the edge of the net. On
both the equal area and equal angle nets, the
strike angles are equally spaced around the net.
This example intersects the edge at 40°
and 220°; by
convention the strike would be given as N40E.The dip is given by the small circles
about the center of the projection (90°
from the intersection of the great circle
with the edge of the diagram),
counting in from the edge of the projection
(which is 0°) or outward
from the center (which is 90°).
This is 4 circles in from the edge, or 40°. The dip direction is to the NW.
It is 90° from the strike, so it is actually
310°, but the convention is merely to indicate
whether the dip is toward the NW or the SE.
Because this is a lower hemisphere projection,
the plane dips down to the NW |

stereo net quiz to develop your ability to measure great circles.

*Last revision *
*10/19/2014*