Digitizing Window EllipseFit is an integrated program for geological finite strain analysis. It is used to derive two and three-dimensional strain from oriented photographs of thin sections, hand samples, or outcrop surfaces, and is designed for laboratory and field based structural geology studies. The intuitive graphical interface and multi-platform deployment also make it ideal for teaching introductory or advanced structural geology laboratories.

Fry Plot Images of oriented sections can be digitized using center-point, ellipse, polygon, and filled polygon methods. Polygon fitting, using moment-equivalent ellipses, allows a wide range of geological objects to be analysed, including ooids, pebbles, fossils, and irregular clasts.

Digitizing Window Graphical strain analysis techniques include Fry graphs, polar Elliott and Rf/Φ diagrams, strain maps, and a variety of polar and cylindrical hyperboloidal projections with automatic contouring.

Best-fit ellipse calculations include shape-matrix eigenvalue, mean radial length, and hyperboloidal vector mean. Shape-matrix error analysis is done analytically and using bootstrap techniques. The initial data set can be unstrained to check variation in the calculated pre-strain fabric.

Strain Map Fitting of ellipse-section data to a best-fit ellipsoid is done using the shape-matrix technique of Shan. Error analysis is done by calculating the section ellipses, and comparing the misfits between calculated and observed section ellipses.

Graphical displays of ellipsoid data include Nadai and Flinn graphs. Data can be directly digitized from photographs, or can be imported using comma or tab delimited spreadsheet files. Graphs can be exported as bitmap images in various formats, or as vector graphics files which can be imported into graphics editing programs, such as Adobe Illustrator.

Wellman Graph EllipseFit was used for teaching strain analysis workshops with Paul Karabinos and Matty Mookerjee at the 2012 Structural Geology and Tectonics Forum, at Williams College, and the 2014 Structural Geology and Tectonics Forum, at the Colorado School of Mines. The newer versions contain additional statistical procedures, progress on the User Manual, tutorial exercises, bug fixes, and new features.

Nadai Plot For Windows installation, download the file EllipseFit_3.3.0_Win.zip by clicking on the link above. Right click on the downloaded file, and select the Extract All option to extract the contents. The resulting folder will contain the EllipseFit application, the User Manual, and example files. You may move this folder anywhere you like, including to a thumb drive. For Macintosh installation download the file EllipseFit_3.3.0_Mac.dmg, double click on it, and drag EllipseFit to your Applications, or other, folder. The User Manual, and Example Files folder should be copied to a directory of your choice. Right click on the application icon to start it for the first time, you may need to modify your Gatekeeper options before OS X will allow this. For Linux installation download the file EllipseFit_3.3.0_Lin.tgz, double click on it, and copy the extracted ellipsefit application, User Manual, and Example Files folder to a directory of your choice.

EllipseFit is written by Frederick W. Vollmer and is free. Please read the accompanying User Manual for information on license, citation and references. EllipseFit is in active development, and user input, bug reports, and suggestions are greatly appreciated.

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