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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It could represent a principal stress for a conjugate fault pair. We can now consider how two lines the ones in green plot.
It is helpful to understand the 3-D geometry that is being represented on the 2-D stereonet projection plane.
The one line is formed by the intersection of the N-S vertical plane and the red plane of interest, and the other by the E-W vertical plane and the red plane of interest. A detailed diagram… Hand written sample. Typically university geology and stereont students are expected create stereonets by hand. Repeat this on another nearby great circle.
This is the bisector. This part needs to be done with pencil and tracing paper, with a stereonet projection underneath. Most figures are made using an equal area projection, but sometimes and equal angle projection is used as well. In work environment, we usually use software to generate stereonets.
As you start plotting points you will see why this is necessary. Equal angle projection 2. The x-axis horizontal stereeonet y-axis vertical coordinates of a latitude-longitude measurement can be calculated using the following formula:. This is the basic 3D geometry we will start with.
Some structural elements whose orientations can be plotted on a stereonet are: J On a new page, plot the following line 40 and then find the family of lines points on the stereonet that is 20 degrees away.
Equal angle projection preserve angle but severely distort areas. This is a very useful tool because it can reduce the workload by avoiding lengthy calculations. sterdonet
Data Input and Output 8. Note that a line plots as point – the point of intersection with the dqual hemisphere. A line is drawn from that projection point to the lower hemisphere intersection point light green dashed lines. The green represents the plane’s orientation when North is rotated back to its standard top-of-the-stereonet position.
The steeper the dip the less curved the great circle is and the closer to the center, and the shallower the dip of the plane the more curved and the closer to the outside margin of the stereonet plot the great circle is.
Nagle are equal area stereonet and equal angle stereonets.
2. Stereonet — InnStereo 0 documentation
The point 1 and 2 are best fit line points for the poles that lies about the center of the diagram. The equal angle stereonets are suitable for kinematic analysis. It may take some timeand focus to understand the geometry. The trend and plunge is given as 89 Along the common great circle containing the two poles count in degree increments half of the angle found in D above. Stereonet Edit on GitHub. It is the outer most circle is the primitive. In other words, it is often used to analyze accuracy of data from several different regions of the same area.
If you are a mineralogist, you will use the top half of the spherical projection for crystallographic analysis.
A circle on the surface of a sphere made by the intersections of a plane that does not pass through the center of the sphere.
Stereographic projection for structural analysis
The diagrams below attempt to show you that geometry in three stages, each more complex. It is measured on the great circle itself. The software often eliminates many user errors, produce much better quality steronets extremely detailed analysis of datasets and make it easier to share with other over electronic devices.
The reasoning behind which hemisphere we used is more conceptual than anything.