Plot the Pole to a Plane, Given its Strike and Dip

Steven Dutch, Professor Emeritus, Natural and Applied Sciences, University of Wisconsin - Green Bay

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The pole to a plane is 90 degrees away from every point on the great circle that represents the plane. To plot a pole, we go through the same procedures as to plot a great circle, except that when we count off the dip, we count an additional 90 degrees. Since we count dip in from the primitive circle to plot the great circle, we plot the pole by counting the dip out from the center of the net, in the opposite direction from the dip.

The diagram at right shows why.

Example

1. Mark the strike of the plane and sketch a strike and dip symbol. 2. Rotate the strike until it is north-south. Count off the dip of the plane. An additional 90 degrees in the same direction locates the pole. Note that this is the same as counting off the dip outward from the center of the net in the direction opposite the dip. 3. Mark the pole. The corresponding great circle is shown in light green. 4. Rotate the overlay to its original position.

The great circle is shown in the example for clarity to illustrate the relationship between the pole and the great circle. It is not necessary (and usually not recommended) to draw the great circle in practice.

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Created 12 April 1999, Last Update 12 April 1999