Using Computer Vision Photogrammetry (Agisoft PhotoScan) to Record and Analyze Underwater Shipwreck Sites

In 2010, a new off-the-shelf software for Computer Vision Photogrammetry, Agisoft PhotoScan, became available to nautical archeologists, and this technology has since become a popular method for recording underwater shipwreck sites. Today (2015), there are still active discussions regarding the accuracy and usage of Computer Vision Photogrammetry in the discipline of nautical archaeology. The author believes that creating a 1:1 scale constrained photogrammetric model of a submerged shipwreck site is not difficult as long as archaeologists first establish a local coordinate system of the site. After creation of a 1:1 scale constrained photogrammetric model, any measurements of the site can be obtained from the created 3D model and its digital data. This means that archaeologists never need to revisit the archaeological site to take additional measurements. Thus, Computer Vision Photogrammetry can substantially reduce archaeologists’ working time in water, and maximize quantity and quality of the data acquired. Furthermore, the author believes that the acquired photogrammetric data can be utilized in traditional ship reconstruction and other general studies of shipwrecks. With this idea, the author composed a new methodology that fuses Computer Vision Photogrammetry and other digital tools into traditional research methods of nautical archaeology. Using this method, archaeologists can create 3D models that accurately represent submerged cultural heritage sites, and these can be used as representative archaeological data. These types of representative data include (but are not limited to) site plans, technical artifact or timber drawings, shipwreck section profiles, georeferenced archaeological information databases, site-monitoring systems, digital hull fragment models and many other types of usable and practical 3D models. In this dissertation, the author explains his methodology and related new ideas

Portuguese Ships on Japanese Namban Screens

Namban screens are a well-known Japanese art form that was produced between the end of the 16th century and throughout the 17th century. More than 90 of these screens survive today. They possess substantial historical value because they display scenes of the first European activities in Japan. Among the subjects depicted on Namban screens, some of the most intriguing are ships: the European ships of the Age of Discovery. Namban screens were created by skillful Japanese traditional painters who had the utmost respect for detail, and yet the European ships they depicted are often anachronistic and strangely. On maps of the Age of Discovery, the author discovered representations of ships that are remarkably similar to the ships represented on the Namban screens. Considering the hypothesis that ships of some of the Namban screens are copies of ships represented on contemporary European cartography, the author realized that one particular historical event connecting Europe and Japan may be the source of these representations. This was the first visit of the Japanese Christian embassy, the Tensho Embassy, to Rome, in 1582. Its journey to Europe and its following visit to the Taiko, or first effective leader of Japan, Hideyoshi Toyotomi, may have been a trigger for the production of one of the most well-known Japanese artworks, the Namban screens

The DistoX2: a methodological solution to archaeological mapping in poorly accessible environments

Spatial information is crucial to archaeological field research. From the plane-table to the total station, recent technological advances have enabled data collection to become fully digital and highly accurate. Nevertheless, the recent expansion of archaeological expeditions to novel environments often incompatible with modern mapping equipment, e.g. tropical forests or ephemeral shorelines, calls for further methodological innovations. Such projects, as well as those under logistic or financial limitations, are still largely reliant on more time consuming, less accurate, traditional approaches, e.g. offset or tape and compass methods. The DistoX2 is a digital, highly portable, and versatile hand-held instrument originally developed for speleological surveys where total stations and DGPSs are not feasible. However, the potential of the DistoX2 system as a spatial mapping tool in above-ground contexts has been surprisingly overlooked. Here, we present a first assessment of the applicability of the DistoX2 for archaeological mapping in non-speleological environments. We investigate precision and accuracy in controlled above-ground settings relative to two common methods of data collection - total station, and tape and compass. We test the relative precision of the DistoX2 when mounted on a tripod or operated in hand-held mode and discuss its applicability, and potential combined used, in the context of other increasingly popular methods - GNSS and SfM photogrammetry. With a mean error of approximate to 5.00 cm for horizontal readings and approximate to 2.00 cm for vertical readings, the DistoX2 is considerably more accurate than the tape and compass method (mu approximate to 67.00 cm horizontal; mu approximate to 3.00 cm vertical). While the DistoX2 exceeds the error thresholds of projects that require high spatial sensitivity (e.g. Palaeolithic excavations), it provides a reliable, low-cost and more accurate alternative to many projects that resort to more traditional methods. This fills an existent methodological and financial gap amongst the growing diversity of archaeological expeditions.SFRH/BD/115085/2016; UIDB/04211/2020; EC-399R-18info:eu-repo/semantics/publishedVersio

From Boatyard to Museum: 3D laser scanning and digital modelling of the Qatar Museums watercraft collection, Doha, Qatar

This is the final version of the article. Available from Wiley via the DOI in this record.This article presents the results of a project to 3D laser scan and digitally model 14 watercraft from the Qatar Museums collection, comprising a range of regional vessels: most had not been surveyed previously. The project used the resulting point clouds generated 2D naval lines and orthographic records of the vessels in their current condition, and photorealistic 3D digital models for gallery display. This case study provides illustrative examples of the intermediate stages and final outputs. It assesses the pros and cons of 3D laser scanning as a survey technology for nautical scholars in terms of the time, cost, and skillset, as well as logistical considerations. It also compares the accuracy of traditional hand survey methods.We wish to thank QM for enabling and funding this research (Grant number SL-05894)

Image-based underwater 3d reconstruction for cultural heritage: from image collection to 3d. critical steps and considerations

Underwater Cultural Heritage (CH) sites are widely spread; from ruins in coastlines up to shipwrecks in deep. The documentation and preservation of this heritage is an obligation of the mankind, dictated also by the international treaties like the Convention on the Protection of the Underwater Cultural Heritage which fosters the use of “non-destructive techniques and survey methods in preference over the recovery of objects”. However, submerged CH lacks in protection and monitoring in regards to the land CH and nowadays recording and documenting, for digital preservation as well as dissemination through VR to wide public, is of most importance. At the same time, it is most difficult to document it, due to inherent restrictions posed by the environment. In order to create high detailed textured 3D models, optical sensors and photogrammetric techniques seems to be the best solution. This chapter discusses critical aspects of all phases of image based underwater 3D reconstruction process, from data acquisition and data preparation using colour restoration and colour enhancement algorithms to Structure from Motion (SfM) and Multi-View Stereo (MVS) techniques to produce an accurate, precise and complete 3D model for a number of applications