A low-cost approach for determination of discontinuity orientation using smartphone images and application to a part of Ihlara Valley (Central Turkey)

Assessment of discontinuity controlled failure phenomena over large areas is extremely hard or even impossible due to the difficulties encountered at the data collection stage. Conventionally, the data collection has been made by engineering geologists via field surveys using compass and measurement tapes. The present study proposes a new low-cost and practical approach by using mobile phones and photogrammetric methods, which allows the measurement of orientation (strike and dip) of discontinuity in a computerized environment. The images acquired using a smartphone camera provide the means for highly representative surface modeling via dense image matching. Such dense measurements reduce the errors caused by sparse sampling of discontinuity surfaces. The kinematic analysis based on the orientation data obtained from the proposed methodology shows the discontinuity controlled failure susceptibility. The methodology proposed here has been applied to a part of Ihlara Valley in Cappadocia Region (Central Turkey), which has columnar structures that are extremely difficult to survey with conventional field works. The application of the proposed methodology yields successful and promising results for large and inaccessible terrain types. Although a major improvement to the proposed methodology would be using the geolocation and rotation of the images obtained from the sensors of the phone directly (thus eliminating the need for external control points with known ground coordinates), the procedure described in this study is low-cost and do not require extensive knowledge on photogrammetry for engineering geologists.