equal area stereonet with small circles showing consistent size. Small circles Angles are slightly distorted and make the circles appear as ellipses. The x-axis. This is a printable 2 degree equal angle (Wulff) stereonet in PDF format. Equal angle versus Equal area nets. Two projections used in structural geology. They are also used as map projections, and for maps of the sky in astronomy (or .

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In other words, it is often used to analyze accuracy of data from several different regions of the same area. The green arrow represents the rate of drop with respect to the original block. Ajgle Determining the angle between the two lines by counting along the common great circle in degree increments from one to the other line.

If it is less than 90 degrees it is the acute angle, otherwise it is the obtuse angle. In most cases it is preferable to use a projection that optimises equal area, because it makes it easier to assess the spatial distribution of structures. There are ahgle no differences between the interpretations made using manual drawing and software-based drawing of datasets.

However, the equal area steronets will reduce the area distortion. Small qngle run left-right latitudinal on the stereonets and are perpendicular to the great circles. It is helpful to understand the 3-D geometry that is being represented on the 2-D stereonet projection plane.


Equal Angle (Wulff) Stereonet

The analysis and interpretation of data achieved through the use of either equal area of equal angle steronets should result in same conclusions. It could represent a principal stress for a conjugate fault pair.

Equal area projection 2. Then count along that great circle in degree increments moving from one steroenet pole to the other.

It is also useful in structure equap contouring. If you are a mineralogist, you will use the top half of the spherical projection for crystallographic analysis.

D Finding the angle between the poles and thus between the two planes. The stereonet or stereographic projection is the most important visualization tool for orientation data in structural geology.

A Plot the following two planes: Structural Analysis Using Stereonets 2 weeks, focus on the Arbuckles 30 pts. Angles are slightly distorted and make the circles appear as ellipses. The reasoning behind which hemisphere we used is more conceptual than anything. Planes and lines whose orientation is being plotted all pass through the center. This is the bisector. If the same plane was rotated about a vertical axis in the stereonet center, they would then retain their dip, but have a different strike.

In this position it is easy to trace out the great circle with the appropriate dip, here 50 degrees to the NE.

Most figures are made using an equal area projection, but sometimes and equal angle projection is used as well. What is important to someone who just started using steronets is to recognize that steronets represents half a sphere where the cross section has degrees. This part needs to be done with pencil and tracing paper, with a stereonet projection underneath.


A circle on the surface of the sphere made by the intersection with the spehere of a plane that passes through the center of the sphere. Where the lower hemisphere intersects the horizontal plane is the outward trace of the stereonet plot.

The blue represents the position where you can count the plunge of the anglf star as about 37 degrees. You can do this by simply rotating the point representing the line on to any great circle, and then count along that great circle 20 degrees in both directions and mark those points which will be two lines 20 degrees either side of the first. The horizontal displacement is indicated with the brown arrow vertical displacement is NOT shown.

Read the Docs v: This is the basic 3D geometry we will start with. This is because the equal angle stereonets preserves the true relationships between stratigraphic and structural features. The strike and dip of that great circle is that of the common plane.

Stereographic projection for structural analysis

They are used for analysis of various field data such as bedding attitudes, planes, hinge lines and numerous other structures. Background information on the use of stereonets in structural analysis. The rake of the fault is between the left most edge of the footwall and the displacement vector red. A detailed diagram… Hand written sample.