AUTOMATED 2-DIMENSIONAL STRAIN ANALYSIS FROM DEFORMED ELLIPTICAL MARKERS USING AN IMAGE-ANALYSIS SYSTEM

An image analysis system is used to automate data collection from deformed elliptical markers and calculate strain using computer programs. In the image analysis, best-fit ellipses are calculated for individual binarized markers, and their axial ratios and long-axis orientations are used for strain calculations. The precision of data obtained by our system is within ±11% for axial ratios and within ±3° for long-axis orientations when a marker has an area larger than 360 pixels in an image area of 512 × 480 pixels, and is located in the central part of 256 × 240 pixels. An example of strain analysis from 275 ooids in a deformed oolitic limestone shows that the strain ellipse calculated from the data obtained by image analysis has a ∼3% higher axial ratio and a 2.6° difference in long-axis orientation compared to manual methods. Finite strain analyses can be done automatically and precisely in a short time by using image analysis methods. © 1990.