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.
|Published (Last):||26 July 2011|
|PDF File Size:||19.11 Mb|
|ePub File Size:||14.52 Mb|
|Price:||Free* [*Free Regsitration Required]|
While the equatorial projection produces no infinitesimal area distortion along the equator, this pole-tangent projection instead produces no infinitesimal squal distortion at the south pole.
The analysis and interpretation of data achieved through the use of either equal area of equal angle steronets should result in same conclusions. That great circle is the bisecting plane. The trend and plunge is given as 89 Instead, it is common to use graph paper designed specifically for the task.
Lab 5: Structural Analysis using stereonets
However, the equal area steronets will reduce the area distortion. In geometrythe stereographic projection is a particular mapping function that projects a sphere onto a plane. As before, the stereographic projection is conformal and invertible outside of a “small” set.
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. B Determine the trend and plunge of the intersection. Researchers in structural geology are concerned with the orientations of planes and lines for a number of reasons.
Stereographic projection for structural analysis | Sanuja Senanayake
This construction is used to visualize directional data in crystallography and geology, as described below. Computers now make this task much easier. It is helpful to understand the 3-D geometry that is being represented on the 2-D stereonet projection plane. The stereonet or stereographic projection is the most important visualization tool for orientation data in structural geology.
These lines are sometimes thought of as circles through the point at infinity, or circles of infinite radius. Aitoff Hammer Wiechel Winkel tripel.
The stereographic projection with Tissot’s indicatrix of deformation. There are absolutely no differences between the interpretations made using manual drawing and software-based drawing of datasets.
Remember the convention is that the first number represents the trend direction and the second represents the plunge amount. That is the angle desired. In geology this is usually referred to a Schmidt Netafter Walter Schmidt. The point 1 and 2 are best fit line points for the poles that adea about the center of the diagram.
The values X and Y produced by this projection are exactly twice those produced by the equatorial projection described in the preceding section. The reasoning behind which hemisphere we used is more conceptual than anything. On the Wulff net, the images of the parallels and meridians intersect at right angles.
Typically university geology and engineering students are expected create stereonets by hand. Moeck and Eric Mandell Making sense of nanocrystal lattice fringes, J. There are different methods by which the points of intersection with the lower hemisphere are projected onto the stereonet. Background information on the use of stereonets in structural analysis. sterronet
The fundamental problem of cartography is that no map from the sphere to the plane can accurately represent both angles and areas. The stereographic projection presents the quadric hypersurface as a rational hypersurface.
It is neither isometric nor area-preserving: Equal area projection 2. 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. Circles on the sphere that do pass through the point of projection are projected to straight lines on the plane. This line can be plotted as a point on the disk just as any line through the origin can.
General perspective Gnomonic Orthographic Stereographic. So any set of lines through the origin can be pictured, almost perfectly, as a set of points in a disk. No map from the sphere to the plane can be both conformal and area-preserving.
The first part of 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. The onion skin arex permits you to rotate the points being plotted with respect to the underlying, fixed reference frame.
The stereographic projection was known to HipparchusPtolemy and probably earlier to the Egyptians.
This space is difficult to visualize, because it cannot be embedded in three-dimensional space. Basic Algebraic Geometry I.
Casselman, BillFeature column February