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How to plot a plane and its pole on a stereonet canvas? First, place an overlay paper on top of the stereonet and place a pin at the center of the stereonet to allow the rotation of the overlay on top of the stereonet. The stereonet will be kept fixed at all stage of the procedure. The plotting is done on the overlay, never on the stereonet. Lets plot the plane 035-25SE, first it is alway a good strategy to guess the result. Knowing that the plane is dipping toward the SE you expect a great circle with a curvature pointing toward the SE, furthermore you expect its pole to be on the opposite side somewhere in the NW sector of the stereonet. Now let's plot that bloody plane...
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| First, mark the strike of the plane on the overlay on the outer circle of the stereonet. |
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Then, rotate the overlay so that the mark aligns with the NS diameter of the stereonet. Along the EW diameter locate the great circle 25º as shown below. You have the choice between 2 great circles one on the East sector to other of the West sector. However, only one will dip toward the SE when you will rotate back the stereonet in its fundamental position. Trace the great circle 25ºSE. From that great circle count 90º along the EW diameter and plot a dot. This dot is the stereographic projection of the pole of the plane. |
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Rotate the overlay back in its fundamental position its N aligned with the N of the stereonet. You can now compare this result with your guess. As expected the curvature of the great circle points toward the SE ie the dip direction, and the pole is located on the opposite sector. |
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