c) Equal-area stereonets are used in structural geology because they present b ) The north pole of the stereonet is the upper point where all lines of longitude. Background information on the use of stereonets in structural analysis The above is an equal area stereonet projection showing great circles as arcuate lines. Page 1. mm. WIDTH. Blunt. TUT. HT. T itillinn.

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Equal angle projection 2. The great circle is divided in to degrees like degree protractor because maps are designed based on same azimuthal bearing directional vectors.

2. Stereonet — InnStereo 0 documentation

In this example a projection point exists one sphere radius directly above the center. So the projection lets us visualize planes as circular arcs in the disk.

The stereographic is the only projection that maps all circles on a sphere to circles.

The foliation of a rock is a planar feature that often contains a linear feature called lineation. Most figures are made using an equal area projection, but sometimes and equal angle projection is used as well. Label each one clearly. To find the plunge rotate the intersection point to the vertical equatorial plane and count up from the intersection point to the nearest periphery point in degrees along the equatorial plane – that eqhal your plunge angle.

However, the equal area steronets will reduce the area distortion. Map projections Conformal mapping Conformal projections Crystallography Projective geometry. 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.


Along the common great circle containing the two poles count in degree increments half of the angle found in D above. Then count along that great circle in degree increments moving from one point pole to the other. The stereonets is a type of standardized mapping system that allows us to represent various angles in 3D space on a 1D paper. Differential geometry of curves and surfaces.

This is a very useful tool because it can reduce the workload by avoiding lengthy equsl.

Lab 5: Structural Analysis using stereonets

Not all projections that preserve the orthogonality of parallels and meridians are angle-preserving. Two points P 1 steeronet P 2 are drawn on a transparent sheet tacked at the origin of a Wulff net. Basic Algebraic Geometry I. The projection used for this kind of plots is the Stereographic Projection with equatorial aspect See: This page was last edited on 21 Decemberat That is, crystal axes and poles to stereknet planes are intersected with the northern hemisphere and then plotted using stereographic projection.

Stereographic projection for structural analysis

Small circles run left-right latitudinal on the stereonets and are perpendicular to the great circles. While the equatorial projection produces no infinitesimal area distortion along the equator, this pole-tangent projection instead produces no infinitesimal area distortion at the south pole. On the Wulff net, the images of the parallels and meridians intersect at right angles.

This results in effects known as a little planet when the center of projection is the nadir and a tube when the center of projection is the zenith.

They are hemisphere surface paths from one line being rotated about another line the pole of rotationboth steteonet through the hemisphere center. Those labeled with dip amounts on the left side, dip to the west.


The green represents the plane’s orientation when North is rotated back to its standard top-of-the-stereonet position. Where that line passes through the stereonet project plane is where the line plots the dark green dot. All strike angles are measured with respect to the true North.

Stereographic projection

The stereonef horizontal and y-axis vertical coordinates of a latitude-longitude measurement can be calculated using the following formula:. Note that a line plots as point – the point of intersection with the lower hemisphere. Albers Equidistant Lambert conformal. In other words, S is the locus of zeros of a non-singular quadratic form f x 0That great circle is the bisecting plane. For example, from intersection point 3 upwards towards NW direction of the great circle intersection of plane A.

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 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.

It is neither isometric nor area-preserving: Background information on the use of stereonets in structural analysis. Remember it is always good to know what the black box software program is doing for you.

In geometrythe stereographic projection is a particular mapping function that projects a sphere onto a plane. C Plotting the poles to each of those planes and label them.