EllipseFit

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.

Unstrain 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.

Fry Graph Graphical strain analysis techniques include Fry graphs, polar Elliott and Rf/Φ diagrams, strain maps, and a variety of polar and cylindrical hyperboloidal projections (stereographic, equal area, etc.) with automatic contouring.

Wellman Graph 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.

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.

MLLF Graph Version 3.1.0 is the release that will be used for the 2014 Structural Geology and Tectonics Forum, at the Colorado School of Mines in June, where I will be teaching a strain workshop with Paul Karabinos and Matty Mookerjee. This new version contains additional statistical procedures, including graphical confidence regions, and ellipsoid error analysis. A new implementation is Shan's (2011) mean log likelihood function (MLLF) maximization, an objective procedure for determining strain from Fry-type data. This release also includes significant progress on the User Manual, with tutorial exercises.

For Windows installation, download the file "EllipseFit_3.1.0_Win.zip" by clicking on the link above. Your browser will likely download it to your "Downloads" folder. Open that folder, and drag the file to your Desktop. Right click on the file and select the "Extract All" option to unzip the file onto your Desktop. The resulting folder will contain the EllipseFit application, the User Manual, example files, and support files. You may move this folder anywhere you like, including to a thumb drive. The folder "Resources" must stay in the same folder as the EllipseFit.exe application.

The new User Manual is 60 pages, and can take a long time to load in your browser. I recommend right-clicking on the link and saving it to a local folder. The manual is also included in the software packages.

EllipseFit is written by Frederick W. Vollmer and is freeware. EllipseFit 3 is a major upgrade in active development. Please read the accompanying User Manual file for information on license, citation and references.

Elliott Plots Rf Phi Plots Flinn and Hossack Plots