Method for photogrammetric surveying of archaeological sites with light aerial platforms

In this paper, we describe a complete methodology for performing photogrammetric surveying of archaeological sites using light aerial platforms or unmanned aerial vehicle (UAV) systems. Traditionally, the main problem with using these platforms is the irregular geometry of the photographs obtained. These irregular image block patterns are occasioned by uncontrolled circumstances (e. g. effect of wind, lack of flight control, etc.) which generate high imprecision in the positioning of camera stations. The method proposed here allows the execution of the photogrammetric flight following the predicted parameters determined in mission planning (camera focal length, photo scale, ground sample distance -GSD-, overlaps, etc.) so we can obtain regular flight geometries. Our method allows the use of conventional photogrammetric data reduction methods based on the use of stereoscopic photogrammetric workstations. Although flights with irregular patterns can allow the formation of stereo pairs within certain limits, conventional photogrammetric procedures often have great difficulty in processing these irregular image blocks. For this reason this system raises the staking out of the camera positions by using a robotized total station and a mini prism situated on the platform. This method is applied to a real photogrammetric survey of an archaeological site of the Tartessic epoch in Southern Spain. The results obtained, confirmed by a quality control of the photogrammetric flight, have demonstrated the viability of this methodology even when moderate wind effects appear.     

Surfaces from the Visual Past: Recovering High<Emphasis Type="Bold">-</Emphasis>Resolution Terrain Data from Historic Aerial Imagery for Multitemporal Landscape Analysis

Historic aerial images are invaluable sources of aid to archaeological research. Often collected with large-format photogrammetric quality cameras, these images are potential archives of multidimensional data that can be used to recover information about historic landscapes that have been lost to modern development. However, a lack of camera information for many historic images coupled with physical degradation of their media has often made it difficult to compute geometrically rigorous 3D content from such imagery. While advances in photogrammetry and computer vision over the last two decades have made possible the extraction of accurate and detailed 3D topographical data from high-quality digital images emanating from uncalibrated or unknown cameras, the target source material for these algorithms is normally digital content and thus not negatively affected by the passage of time. In this paper, we present refinements to a computer vision-based workflow for the extraction of 3D data from historic aerial imagery, using readily available software, specific image preprocessing techniques and in-field measurement observations to mitigate some shortcomings of archival imagery and improve extraction of historical digital elevation models (hDEMs) for use in landscape archaeological research. We apply the developed method to a series of historic image sets and modern topographic data covering a period of over 70 years in western Sicily (Italy) and evaluate the outcome. The resulting series of hDEMs form a temporal data stack which is compared with modern high-resolution terrain data using a geomorphic change detection approach, providing a quantification of landscape change through time in extent and depth, and the impact of this change on archaeological resources.     

Multi-temporal archaeological analyses of alluvial landscapes using the photogrammetric restitution of historical flights: a case study of Medellin (Badajoz,Spain)

One of the main challenges affecting the archaeological study of alluvial landscapes is the intensity of change these environments experience over time. Quick and dramatic alterations in geomorphological dynamics and land exploitation determine the visibility and conservation of the archaeological record. This study proposes an approach to the problem of studying these evolving environments based on the analysis and treatment of a series aerial photographs taken between the 1950s and the present day. This paper is particularly interested in looking at the process of photogrammetric restitution and in validating and comparing the digital terrain models and orthoimages produced. The quantitative analysis and visual interpretation of these results can provide valuable information about the transformation of landscapes and factors affecting surface evidence. The intended final result is to develop the ability to map the most problematic or best preserved areas. Nevertheless, it is considered in terms of a relative measure of change magnitude, rather than trying to provide absolute figures.     

COMPUTER VISION‐BASED ORTHOPHOTO MAPPING OF COMPLEX ARCHAEOLOGICAL SITES: THE ANCIENT QUARRY OF PITARANHA (PORTUGAL–SPAIN)

Ancient quarries are intriguing archaeological sites, but their detailed recording is complex. This paper presents a cost‐effective approach to mapping of the Roman quarry site of Pitaranha (Portugal–Spain). First, aerial photographs were acquired using a radio‐controlled digital reflex camera attached to a Helikite, which allowed the acquisition of the necessary low‐altitude aerial footage in the very unstable wind conditions above the quarry. Using computer vision algorithms, the resulting set of photographs was semi‐automatically transformed into a Digital Surface Model (DSM) and a corresponding orthophotograph. Besides focusing on the acquisition and processing method, this paper evaluates the accuracy of the generated products. The orthophotograph proved to be satisfactorily accurate for 1:200 hard‐copy mapping.     

Framing the past: situating the archaeological in photographs

Archaeology continually reproduces its own images. Speaking archaeology’s visual language is one way we prove membership in the discipline. Many aspects of this visual language have become so naturalized within archaeological representation as to be almost unquestionable: the cleaning of the site, the use of scale, and particular framings and perspectives. How, then, is the production of particular photographic images of archaeology related to the practice of archaeology? Does archaeology look a certain way (in photographs) or are archaeologists reproducing an archaeology according to the way it is thought it should look? Using examples of early photographs from Latin American archaeological expeditions, this article investigates not only photography as an applied technology for scientific recording, but also its power to situate archaeological knowledge. Drawing on recent reflective and critical developments in both the history of archaeology and visual anthropology, it uses five focal points – trace, objectivity and authenticity, sight/site, still lifes, and still lives – to argue that early-twentieth-century archaeological photographs of Latin America participated in the generation of an ‘authentic’ past rather than simply paid testament to it.     

Active use of panoramic mobile mapping systems for as built surveying and heritage documentation

Mobile mapping systems (MMS) are widely used technology nowadays for spatial data collection of large scale projects like for city and highway mapping. The systems are mainly equipped with laser scanning sensors and/or imaging sensors mounted on a moving vehicle during the scene capture. Imaging sensors are normally cameras which either capture perspective or panoramic images covering the whole horizon of the vehicle. The orientation of the captured panoramic images is accurate to centimeters’ level because of the precise positioning and navigation systems equipped with these mapping systems. However, the positioning accuracy of mobile mapping systems can be degraded in city centers or urban canyons because of the satellite signal disturbances.

In this article, we discuss the following objectives: (1) the possibility to use the mobile mapping images for cultural heritage documentation and as built surveying and how accurate the mapping can be; (2) the concept of using the mobile mapping images as a tool of georeferencing the crowdsource images; and (3) the efficiency of using the multi-temporal mobile mapping images for occluded free cultural heritage facade orthophotos. The mobile mapping systems of CycloMedia with two panoramic products of Cyclorama images (12 MP) and HD Cycloramas (100 MP) are used for the experimental tests in this research article.     

Children's Understanding of Aerial Photographs

As aerial photographs are widely used in geography education, it is important to know how children's understanding of these representations develops through the school years. We review research that has addressed children's understanding of the content of aerial photographs, and we describe a series of studies in which children used information from aerial photographs to carry out spatial tasks in a large space. We demonstrate that using an aerial photograph can be an aid to subsequently using a map, and we discuss the educational applications of the research with aerial photographs.     

Cropmarks in main field crops enable the identification of a wide spectrum of buried features on archaeological sites in Central Europe

Buried (syn. sunken, sub-surface and sub-soil) archaeological features on arable land can frequently be discovered due to visually detectable changes in crop growth termed cropmarks. The aim of this paper was to demonstrate the range of features identified through cropmarks on aerial photographs in stands of main field crops in the Czech Republic.     

The sky is the limit: reconstructing physical geography from an aerial perspective

In an era of rapid geographical data acquisition, interpretations of remote sensing products are an integral part of many undergraduate geography degree schemes but there are fewer opportunities for collection and processing of primary remote sensing data. Unmanned Aerial Vehicles (UAVs) provide a relatively inexpensive opportunity to introduce the principles and practice of airborne remote sensing into field courses, enabling students to learn about image acquisition, data processing and interpretation of derived products. Two case studies illustrate how a low-cost “DJI Phantom Vision+” UAV can be used by students to acquire images that can be processed using Structure-from-Motion photogrammetry software. Results from a student questionnaire and analysis of assessed student reports showed that using UAVs enhanced student engagement and equipped them with data processing skills. The derivation of bespoke orthophotos and Digital Elevation Models has the potential to provide students with opportunities to gain insight into various remote sensing data quality issues, although additional training is required to maximize this potential. Recognition of the successes and limitations of this teaching intervention provides scope for improving future UAV exercises. UAVs are enabling both a reconstruction of how we measure the Earth’s surface and a reconstruction of how students do fieldwork.     

The Application of Great War Aerial Photography in Battlefield Archaeology: The Example of Flanders

Abstract

During the Great War, millions of aerial photographs of the frontline and area behind the trenches were made by the combatants. Such aerial photographs (APs) are a major source for the study of Great War heritage. Studying the APs required a new methodology, involving the processing of APs in GIS models to produce a detailed inventory of war traces. This approach provides reliable digital and analogue maps on which all visible traces are minutely recorded. Through this, we hope to meet the growing necessity of a professional and scientific archaeological research of the Great War.     

UAV and RPV systems for photogrammetric surveys in archaelogical areas: two tests in the Piedmont region (Italy)

Aerial photogrammetric surveys are usually expensive and the resolution of the acquired images is often limited. For this reason, different innovative systems have been developed and tested in order to perform a photogrammetric survey in an inexpensive way, with high-resolution images. In this context, one of the most promising acquisition techniques is represented by the use of Unmanned Aerial Vehicles (UAVs) equipped with a digital camera.     

Image‐Based Modelling from Unmanned Aerial Vehicle (UAV) Photogrammetry: An Effective,Low‐Cost Tool for Archaeological Applications

The recording and 3D modelling of complex archaeological sites is usually associated with high capital and logistical costs, because the data acquisition must be performed by specialists using expensive surveying sensors (i.e., terrestrial laser scanners, robotic total stations and/or ground‐penetrating radar). This paper presents a novel, low‐cost, user‐friendly photogrammetric tool for generating high‐resolution and scaled 3D models of complex sites. The results obtained with unmanned aerial vehicle (UAV) photogrammetry of an archaeological site indicate that this approach is semi‐automatic, inexpensive and effective, and that it guarantees quality.     

Archaeological Site Information Modelling and Management Based on Close-Range Photogrammetry and GIS

New challenges in management and restoration of archaeological sites require the utilization of advanced technologies and systems to assist in preserving the important legacy of human heritage. These challenges include monitoring and preserving of site landscapes, maintenance and rehabilitation of archaeological structures, and quality and safety management. In this research, an integrated methodology based on photogrammetry and Three-Dimensional (3D) Geographic Information System (GIS) is developed to capture and model essential details needed for the proper management of archaeological sites. Recent advances in digital imagery and modelling utilize photogrammetry as an efficient technique for 3D modelling of archaeological sites to derive accurate measurements of size, shape, position, and texture of objects using two-dimensional digital photographs. Spatial data that include aerial stereo photographs, satellite images, close-range photos, terrestrial surveying and Global Positioning Systems (GPS) are integrated within the design of the proposed model. The approach is validated with a case study of Ajloun Castle, one of the ancient and important preserved structures located in Jordan. Various sequential levels of details have been developed for the castle: Orthophoto, Digital Elevation Model (DEM), structures geometry and site layout and 3D textured model. The suggested methodology is expected to be efficient in modelling and documenting archaeological structures. The developed model is utilized to assess the management of archaeological structures through feasibility analysis, rehabilitation decisions, and safety planning.     

CHOOSING NOT TO LOOK: REPRESENTATION,REPATRIATION, AND HOLOCAUST ATROCITY PHOTOGRAPHY1

This essay considers, from ethical and historical‐critical perspectives, alternatives to unconditional public access to Holocaust atrocity photographs. Photographic images have become the common coin of public awareness and historical information about the Holocaust. For the generations immediately following the genocide, atrocity photos and images of Nazi crimes served as vital testimony. For succeeding generations, however, access to certain “recirculated” images (Barbie Zelizer) has created a sense of familiarity with the Holocaust and with the National Socialist era that may prevent, rather than facilitate, engagement with the historical subject, particularly for students. Few of the victims of the Shoah pictured in either the best known or the least circulated images were willing subjects. As such, the bulk of Holocaust and National Socialist photography should perhaps fall under the same category as the results of Nazi medical experiments: they have been rendered inadmissible because they are ethically compromised materials, made without the participants’consent. While I am not advocating the wholesale destruction of Holocaust photographs, I will suggest that removing them from view or “repatriating” them might serve Holocaust memory better than their reduction to atrocious objects of banal attention. Just as the Native American Grave Protection and Repatriation Act of 1990 provided a mechanism for the reclassification of human remains, from ethnographic to spiritually sacred artifacts, we should consider what a similar reclassification of Holocaust photographs could offer. Have Holocaust atrocity photographs reached the limits of their usefulness as testimony?     

Multi-image Photogrammetry for Underwater Archaeological Site Recording: An Accessible,Diver-Based Approach

This article presents a discussion of recent advances in underwater photogrammetric survey, illustrated by case studies in Scotland and Denmark between 2011 and 2013. Results from field trials are discussed with the aim of illustrating practical low-cost solutions for recording underwater archaeological sites in 3D using photogrammetry and using this data to offer enhanced recording, interpretation and analysis. We argue that the availability of integrated multi-image photogrammetry software, highly light-sensitive digital sensors and wide-aperture compact cameras, now allow for simple work flows with minimal equipment and excellent natural colour images even at depths of up to 30 m. This has changed the possibilities for underwater photogrammetric recording, which can now be done on a small scale, through the use of a single camera and automated work flow. The intention of this paper is to demonstrate the quality and versatility of the ‘one camera/ambient light/integrated software’ technique through the case studies presented and the results derived from this process. We also demonstrate how the 3D data generated can be subjected to surface analysis techniques to enhance detail and to generate data-driven fly-throughs and reconstructions, opening the door to new avenues of engagement with both specialists and the wider public.     

Practical Application of Digital Photogrammetry for Fieldwork in the American Midwest: An Example from the Middle Ohio Valley

The use of close-range digital photogrammetry for field documentation has been steadily increasing in the past half decade in several parts of the world. However, this technology has not been widely utilized in archaeological contexts in the American Midwest. We explore the utility of close-range photogrammetry in this region with examples from the Guard site (12D29), a Fort Ancient village located in southeastern Indiana. This article outlines the methods utilized for production of georeferenced 3-D models of several units excavated during the 2016 field season. These models as well as plan and profile orthophotos derived from them act as important supplements to standard photographs and drawings made in the field and easily integrate with the site GIS. Overall, we found close-range digital photogrammetry to be very useful to better document excavation details, doing so for limited cost and time expenditure.     

The Outside Inside: Combining Aerial Photographs, Cropmarks and Landscape Experience

This paper seeks to make a contribution to current debates concerning the dislocation in landscape research between experiential approaches and quantitative techniques of landscape analysis. It focuses upon a group of archaeological sites that are caught in the centre of this divide: plough-levelled sites recorded as cropmarks on aerial photographs. The application of experiential landscape analysis to plough-levelled sites is explored, along with the value of incorporating information derived from the study of the aerial photograph. It is contended that richer, more rounded, interpretations of landscape are possible when combining aspects of quantitative and qualitative landscape research.     

The use of stereoscopic images taken from a microdrone for the documentation of heritage – An example from the Tuekta burial mounds in the Russian Altay

To analyse, interpret and manage our cultural heritage it is important to have an accurate and realistic representation of it. Documenting this heritage involves geographic techniques such as photogrammetry, for which a lot of rather expensive and extensive platforms are already in use. However, a microdrone, a recently developed unmanned aerial vehicle platform is a cheaper and easy to handle tool. To test the very limits of the microdrone and its accompanying data-acquisition and data-processing software, we collected data from a remote area in Tuekta, in the Russian Altay Mountains. This paper presents the challenges faced during the whole photogrammetric procedure from planning the flights to producing the final deliverables.