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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The first part eqyal your stereonet lab will explore the mechanics of manually plotting elements on a stereonet, while the second part will focus using computer programs to contour data and make analysis. What is the form that results? It is measured on the great circle itself.

They are hemisphere surface paths from one line being rotated about another line the pole of rotationboth passing through the hemisphere center. Data Input and Output 8. The analysis and interpretation of data achieved through the use of either equal area of equal angle steronets should result in same conclusions.

To do this rotate the two lines until they fall on one great circle. A line is drawn from that projection point to the lower hemisphere intersection point light green dashed lines.

All strike angles are anglw with respect to the true Steeronet. The projection that is usually chosen for this, is the Lambert Azimuthal Equal-Area Projection with equatorial aspect See: Primitive circle is also a great circle but, it contains N, E, S and W directions at, and degrees intervals. It may take some timeand focus to understand the geometry. Label each one clearly. The stereonets is a type of standardized mapping system that allows us to represent various angles in 3D space on a 1D paper.

In this case the North position is designated in blue. The blue plane position is where North has been rotated so that the great circles all have a strike of N45W The stereographic projection is a methodology used in structural geology and engineering eaual analyze orientation of lines and planes with respect to each other.

## Stereographic projection for structural analysis

In the above diagram two planes are plotted, one red, one blue. The horizontal displacement is indicated with the brown arrow vertical displacement is NOT shown.

B Determine the trend and plunge of the intersection. Remember the convention is that the first number represents the trend direction and the second represents the plunge amount.

If you have understand how 3D vectors anvle, this should be a no-brainer. Equal angle projection 2. There are two widely used types and may be more of stereonets by structural geologists. The green arrow represents the rate of drop with respect to the original block.

It could represent a principal stress for a conjugate fault pair.

### Equal Angle (Wulff) Stereonet

However, the equal area steronets will reduce the area distortion. The green represents the plane’s amgle when North is rotated back to its standard top-of-the-stereonet position.

The strike and dips are given to the left. The point you arrive represents a line perpendicular to the plane you started with, i.

Hence, most educational institutions prefer equal area steronets for their students over the equal angle stereonets. The choice either should not affect the data analysis. 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.

What is plotted on the stereonet is a projection of where a given line or plane intersects the lower hemisphere surface.

The open and filled red stars represent two lines solid 58, open 37 and the dashed red great circle represents their common plane with a strike of SE.