Low cost digital close range photogrammetric measurement of an as-built anchor handling tug hull

A close range photogrammetric (CRP) model of an as-built 40 m anchor handling tug hull located in an open space shipyard was constructed in this study through the use of a low cost amateur digital single-lens reflex camera, together with a modestly priced photogrammetric software. Through a series of comprehensive statistical tests, the constructed CRP tug hull model was quantitatively evaluated and analyzed by comparing the CRP measurements with the manually measured tug hull offset data from a lines-plan drawing. The statistical tests showed that most of the measured target coordinates were considerably accurate in this study, with absolute mean of error 4.1 mm and absolute standard deviation of error ±4.5 mm. Paired Student t-test showed that the modeled CRP Z-offset data (ZCRP) is not statistically different from the actual Z-offset data, ZOFF (p>0.05). Linear regression analysis also illustrates a near perfect linear relationship between these two variables. The accuracy achieved in this study is considerably good and sufficient for usual metrological measurement in small- or medium-sized shipbuilding industry, despites the presence of disturbances related to the characteristics of the open space shipyard. In future, a better targeting approach or target material should be used to further improve the CRP measurement accuracy.