Abstract
Abstract. The paper reports the results of a photogrammetric survey made using an Unmanned Aerial Vehicle (UAV) in the archaeological site of the Roman Amphitheatre in Avella (Avellino, Italy). The aim of the study is to verify which modality of image acquisition (if only nadiral images or nadiral plus Oblique images), together with the method of Global Positioning Satellite System (GNSS) survey of the Ground Control Points (GCP) is able to produce the better 3D model, in terms of accuracy, in order to extract traditional graphic drawings (plan, elevation and section), suited to the required representation scales (1 : 100 and 1 : 50). The accuracy in georeferencing was evaluated analysing the residues on the GCPs; subsequently, a more detailed analysis of the accuracy of the final 3D model was performed analysing the residuals on the image coordinates, also called re-projection error. The method developed is based on the statistical analysis of the different models, built changing the GCPs survey method and the photogrammetric shots acquired. The results of our analysis show that the photogrammetric survey is more ‘stable’ using only nadiral images and that the nRTK technique allows results comparable to those obtained with static measurements, both in precision and in reliability. Moreover, if the GCPs are measured in nRTK mode, taking into consideration the graphical error, the maximum representation scale is 1 : 100, whereas the use of static technique makes it possible to describe major details, at a scale of 1 : 50.
Highlights
IntroductionThe use of photogrammetry for digital 3D recording has undergone a considerable increase of the applications
For the last decade, the use of photogrammetry for digital 3D recording has undergone a considerable increase of the applications
The accuracy in georeferencing was evaluated analysing the residues on the Ground Control Points (GCP); subsequently, a more detailed analysis of the accuracy of the final 3D model was performed analysing the residuals on the image coordinates, called reprojection error computed values within the adjustment process, this is the accuracy of the Tie-Points after the optimization by the bundle adjustment with the GCPs coordinates
Summary
The use of photogrammetry for digital 3D recording has undergone a considerable increase of the applications. With the passing of time, the overall situation gradually transitioned from the common use of scientific applications for 3D surveying with dense clouds realized with the laser scanner technology, to an increasing use of photogrammetry, thanks to the introduction of the automatic Structure of Motion technology. UAV systems for photogrammetric purposes were often used in the archaeological field for the threedimensional survey of complex structures such as the Roman Amphitheatres. The factors that favoured the acquisitions with UAVs, compared to the more classical ones (TLS - Terrestrial Laser Scanner, for example), are mainly: a lower instrument cost, a greater speed of data collection in the field and above all a better colorimetric result of the 3D model, necessary for a correct analysis and archaeological characterization (Remondino et al, 2011; Rinaudo et al, 2012)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
