Accuracy evaluation of a smartphone-based technology for coastal monitoring

This paper introduces a smartphone-based technique for coastal monitoring and evaluates the accuracy of data such as images, three-dimensional coordinates, and attitude that can be acquired by such a technique. First, to determine intrinsic orientation (10) parameters of a smartphone camera, a camera calibration was performed. The results were similar or slightly better than previous studies using a non-metric camera. 3-D coordinates provided by the assisted GPS (A-GPS) embedded in the smartphone showed lower accuracy. Attitudes calculated using an accelerometer and magnetometer showed 0.33-2.04 degrees standard deviation, compared with omega, phi, and kappa of extrinsic orientation (EO) parameters. Additionally, accuracy (RMSE 0.681 pixels) of smartphone image triangulation using ground control points (GCPs) was about equal to the RMSE of 0.404 pixels of a metric camera. Finally, ortho-rectified images of a test field were generated using DEM from terrestrial laser scanning and acquired images. Additionally, mapping of a shoreline was performed using the ortho-rectified images, and a profile of a representative cross-shore was composed. The results described the actual intertidal zone well. Given the results of the cross-shore profile and the horizontal and vertical accuracy evaluation of the extracted shoreline, this smartphone-based technique is considered appropriate for applications in coastal monitoring. (C) 2012 Elsevier Ltd. All rights reserved.