Orient is for plotting and analyzing orientation data - data that can be described by an axis or a direction in space or, equivalently, by a position on a sphere or circle. Examples of data that are represented by unit vectors (vectorial or directed data) or axes (axial or undirected data) include: geologic bedding planes, faults and fault slip directions, fold axes, paleomagnetic vectors, glacial striations, wind and current flow directions, optical axes in quartz and ice crystals, earthquake epicenters, arrival directions of cosmic rays, normals to comet orbital planes, and positions of galaxies.
Spherical projections are used to display three dimensional orientation data by projecting the surface of a sphere, or a hemisphere, onto a plane. Lines and planes in space are considered to pass through the center of a unit sphere, so lines are represented by the two diametrically opposed piercing points. Planes are represented by the great circle generated by their intersection with the sphere or, more compactly, by their normal.
Spherical projections include equal-area (used on a Schmidt net), stereographic (used on a Wulff net or stereonet), and orthographic projections, these can be plotted on either upper or lower hemispheres. Point distributions are analysed by contouring and by computing their eigenvectors (axial data) or vector means (vectorial data). Data sets and projections can be rotated about any axis in space, or to the principal axes. For two-dimensional data, such as wind or current directions, circular plots and circular histograms, including rose, equal-area rose, and kite diagrams can be plotted.
Data may be input as spherical coordinates, longitude and latitude, azimuth and altitude, declination and inclination, trend and plunge, strike and dip, or other measurements. Orient is also used to analyze fault data, which is represented by a fault plane orientation and the direction of slip within that plane. From these data Orient can generate P (Pressure) and T (Tension) axes, which are related to principal stress directions, M (Movement) planes, and slip linears, which indicate displacement directions.
Spherical projections represent orientations, but not spacial locations. Orient uses map analysis to further analyze the spacial distributions of orientation data. For example in structural geology the location of domains of cylindrical folding, where bedding or other layers share a common fold axis, is of interest. Orient's domain analysis features subdivide a map region into multiple domains by maximizing an eigenvalue-based index.
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