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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The transparent sheet is rotated and the central angle is read along the common meridian to both points P 1 and P 2. The above is an equal area stereonet projection showing great circles afea arcuate lines connecting the North and South Points and small circles as arcuate lines in a latitudinal type position.
However, for graphing by hand these formulas are unwieldy.
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 stereographic projection gives an alternative parametrization of the unit circle:. In this case the Steeronet position is designated in blue.
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. Researchers in structural geology are concerned with xrea orientations of planes and lines for a number of reasons. The stereographic projection relates to the plane inversion in a simple way.
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. Although any stereographic projection misses one point on the sphere the projection pointthe entire sphere can be mapped using two projections from distinct projection points. 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.
Plane B rake is downwards towards SE direction. In general, one can define a stereographic projection from any point Q on the sphere onto any plane E such that. The loxodromes of the sphere map to curves on the plane of the form. In geometrythe stereographic projection is a particular mapping function that projects a sphere onto a plane.
A Mathematician Looks at Maps”.
Some fisheye lenses use a stereographic projection steronet capture a wide-angle view. As in crystallography, planes are typically plotted by their poles. The equal-area lower-hemisphere projection defined by the Lambert azimuthal equal-area projection is also used, especially when the plot is to be subjected to subsequent statistical analysis such as density contouring.
If the grid is made finer, this ratio approaches exactly 4. These lines are sometimes thought of as circles arrea the point at infinity, or circles of infinite radius.
Casselman, BillFeature column February What is the form that results? Those labeled with dip amounts on the left side, dip to the west.
In other words, it is often used to analyze accuracy of data from several different regions of the same area. If it were, then it would be a local isometry and would preserve Gaussian curvature. There are absolutely no differences between the interpretations made using manual drawing and software-based drawing of datasets.
Primitive circle is also a great circle but, it contains N, E, S and W directions at, and degrees intervals. Similar remarks hold about the real projective planebut the intersection stereoner are different there.
The point you arrive represents a line perpendicular to the plane you started with, i. These spirals intersect radial lines in the plane at equal angles, just as the loxodromes intersect meridians on the sphere at equal angles. The stereographic projection has been used to map spherical panoramas.
On the Wulff net, the images of the parallels and meridians intersect at right angles.
H Determining the strike and dip of the common plane those two lines define. Also, there are many ways to rewrite these formulas using trigonometric identities. Not all wtereonet that preserve the orthogonality of parallels and meridians are angle-preserving.
The great circles represent north-south striking planes with dips in 10 degree increments. Views Read Edit View history. This will be explained in depth in a different article. The foliation of a rock is a planar feature that often contains a linear feature called lineation.