The theoretical work is benchmarked against laboratory tests using 4 samples with predesigned crack widths of 1-7mm scanned at orthogonal distances of 5.0-12.5m and at angles of 0˚-30˚. Results showed that absolute errors of crack width were mostly less than 1.37mm when the orthogonal distance varied 5.0-7.5m but significantly increased for greater distances. Orthogonal distance had a disproportionately negative effect compared to the scan angle.