Mapping by matching: a computer vision-based approach to fast and accurate georeferencing of archaeological aerial photographs

To date, aerial archaeologists generally apply simple rectification procedures or more expensive and time-consuming orthorectification algorithms to correct their aerial photographs in varying degrees for geometrical deformations induced by the topographical relief, the tilt of the camera axis and the distortion of the optics. Irrespective of the method applied, the georeferencing of the images is commonly determined with ground control points, whose measurement and identification is a time-consuming operation and often limits certain images from being accurately georeferenced. Moreover, specialised software, certain photogrammetric skills, and experience are required. Thanks to the recent advances in the fields of computer vision and photogrammetry as well as the improvements in processing power, it is currently possible to generate orthophotos of large, almost randomly collected aerial photographs in a straightforward and nearly automatic way. This paper presents a computer vision-based approach that is complemented by proven photogrammetric principles to generate orthophotos from a range of uncalibrated oblique and vertical aerial frame images. In a first phase, the method uses algorithms that automatically compute the viewpoint of each photograph as well as a sparse 3D geometric representation of the scene that is imaged. Afterwards, dense reconstruction algorithms are applied to yield a three-dimensional surface model. After georeferencing this model, it can be used to create any kind of orthophoto out of the initial aerial views. To prove the benefits of this approach in comparison to the most common ways of georeferencing aerial imagery, several archaeological case studies are presented. Not only will they showcase the easy workflow and accuracy of the results, but they will also prove that this approach moves beyond current restrictions due to its applicability to datasets that were previously thought to be unsuited for convenient georeferencing.     

The impossibility of resurrecting the past: Reconstructions on archaeological excavation sites

Abstract

Since the beginnings of archaeological research, scientists have attempted to explain the past to a larger public. In the nineteenth century the quality of reconstruction drawings by architects was high but, after excavations were finished, the sites were left as they were, without conservation, while the movable finds were exhibited in the great museums of the European capitals. Today's mass tourism, however, demands attractions at the original ancient sites. The tourist industry, which brings by far the largest pool of visitors to the sites, sets the standards, but its interests centre on quick and simple ‘consumption’ of impressive ruins. Different methods have been employed in creating tourist attractions – from reconstructing ancient buildings to having museum staff in costume demonstrate elements of daily life in history. But it is the ruins on excavation sites, even in their damaged state, that are the irreplaceable, authentic records of the past. Archaeological preservation, therefore, has to mean uncompromising conservation of the damaged original remains. They should not be sacrificed for the sake of questionable ‘progress’ or popularization.     

Charcoal analysis and dendrology: data from archaeological sites in north-western France

During the last 15 years, charcoal analysis of archaeological sites in north-western France has been carried out in conjunction with systematic and detailed dendrological examination. By considering these extrinsic criteria in association with the analytical results, palaeo-ethnographic and palaeo-environmental information can be obtained. The charcoals are classically identified under the microscope on the basis of their cellular structure. This examination is associated with an observation of the ligneous structure on transverse sections using a binocular lens. When charcoal fragments are large enough, the growth ring widths are measured. Tree ring curvature is also noted. Finally, alteration by fusion or radial cracks, the presence of fungal hyphae, and insect degradation are also recorded. Results are thus obtained on the nature of fuel used in domestic fireplaces and kilns. The selection of timbers and their catchment areas are also revealed. The average width of the growth rings in oak charcoal from domestic hearths coming from about forty sites in north-western France shows a significant increase from 6000 to 2000 BP. There is a similar increase in the number of heliophilic taxa used from the Neolithic to the Iron Age. This implies that the environment became more and more open because of use by society. The interpretation of the dendrology results applied to charcoal analyses is obtained through a convergence of criteria. Thus, charcoal analysis can provide more than just an identification of the species used, and can yield fundamental information on the interaction of society with the environment.     

The estimation of live fish size from archaeological cranial bones of the New Zealand blue cod Parapercis colias

Twenty-four measurements were taken on five of the paired cranial bones and the otoliths of a modern sample of 177 blue cod. Parapercis colias. Regression analysis was performed on these measurements to estimate live fork length and ungutted weight. A number of regression models were examined (linear, logarithmic, exponential and power curve) to work out the optimum estimator for each bone measurement. It was found that live fork length of this species can be estimated with a standard error of less than ±28 mm, and the weight to less than ±140 g. Coefficients are provided for 48 equations linking bone size to live characteristics. This is followed by a study of blue cod from an archaeological site at Waihora in the Chatham Islands. Measurements were made on 8036 archaeological bones with a minimum number of individuals of 2547. It was found that the blue cod catch had near normal characteristics, with a mean fork length of 327 mm and SD of 57 mm. The mean body weight was estimated at 569 g. The usable meat weight represented by these fish is estimated to be 1.0 t. © 1997 John Wiley & Sons, Ltd.     

Monitoring the burial environment of terrestrial wet archaeological sites in The Netherlands

Abstract

Monitoring the burial environment of archaeological sites is necessary to assess the success of their preservation in situ. Also, monitoring the state of preservation of actual archaeological remains together with that of their burial environment will further our understanding of the degradation processes acting on archaeological remains in situ. These remains consist not only of objects made from wood, metal, stone, etc., but also of pollen, soil features and even micromorphological features. Although, to date, the precise degradation mechanisms of archaeological remains in situ are not yet fully understood, general agreement exists on which parameters should be monitored in wet terrestrial environments. Also, it has been established that in situ measurements are preferable to laboratory analyses of soil (water) samples. In practice, it is difficult to find suitable monitoring equipment for in situ measurement as it must meet many requirements: an in situ measuring principle; stable for a period of at least several months; robust for use in the field; and equipped with a datalogger. A suitable principle exists for measuring the redox potential, however a simple, robust field instrument with datalogger is not yet available. Monitoring of the water table level, temperature and oxygen content is possible with recently developed, commercially available instruments. Monitoring of acidity is less complex as it does not vary as rapidly as, for example, the redox potential; however, the recommended method is still based on analysing soil samples, which is not acceptable in the long term at archaeological sites.     

The archaeological significance of animal bones from Acheulean sites in southern Africa

Acheulean faunal samples from southern Africa usually contain taxa which are unknown in Upper Pleistocene or Holocene contexts and which suggest that the associated artifacts date mainly from the Middle Pleistocene or possibly the late Lower Pleistocene, between perhaps 1,000,000 and 130,000 years ago. Together with sedimentological evidence, the faunas also indicate that the associated Acheulean people enjoyed unusually moist conditions. There is in fact no evidence for Acheulean presence under conditions as dry as, or drier than, historic ones. The available faunas come mainly from open-air contexts where natural deaths, carnivore killing and scavenging, and possible human hunting and butchering are scrambled, and no direct inferences can be drawn about Acheulean hunting ability. However, if it is fair to extrapolate backwards from their better-documented Middle Stone Age successors, Acheulean people probably rarely, if ever, killed the large ungulates that are so common in their sites.

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Résumé Parmi les ensembles de la faune acheuléenne provenant de l'Afrique du sud se trouvent souvent des taxa qui sont inconnus dans les gisements de l'âge holocène ou du pleistocène supérieur. Cette observation nous amène à suggérer que les outils associés avec cette faune datent principalement du Pleistocène moyen ou peut-être même du Pleistocène inférieur tardif, dans la période, 1,000,000 à 130,000 BP environ. Ces faunes, considérées conjointement avec les témoignages sédimentologiques, montrent que ces gens acheuléens ont profités d'un climat anormalement humide. A vrai dire, il n'y a aucune preuve d'une occupation acheuléenne dans des conditions aussi sèches ou plus sèches que celles de l'époque historique. La plupart des faunes dont on dispose aujourd'hui proviennent des gisements de plein-air ou les évidences de la mortalité naturelle, les restes de la proie des carnassiers, et par l'homme sont mélangées, et nous ne sommes pas permis d'en déduire des conclusions au sujet de la compétence des populations acheuléennes au niveau de la chasse. Si cependant on peut extrapoler en arrière de leurs successeurs mieux connus de l'âge de la pierre moyen, il est vraisemblable que les hommes acheuléens n'ont jamais, ou presque jamais, tués les grands ongulés dont les restes sont si nombreux dans leur sites.

     

The geochronological potential of isoleucine epimerisation in cassowary and megapode eggshells from archaeological sites

Our research demonstrates that the extent of isoleucine epimerisation (A/I) in fragments of avian eggshells provides geochronological information in archaeological contexts. In the archaeological sequence of Hay Cave, northern Queensland, Australia, there is an excellent correspondence between the A/I values of Australian brush-turkey (Alectura lathami) eggshells (n = 99) and independent geochronological control (n = 16 radiocarbon ages including 4 on eggshell calcite). The A/I values identify three phases of deposition during the Holocene at Hay Cave. In contrast to the Alectura eggshell A/I values, a poor correspondence was observed between the A/I values of cassowary (Casuarius) eggshells from Toé (n = 35) and Kria caves (n = 23) (Ayamaru Plateau, Papua) and the depths from which the specimens were recovered in these stratified sequences. Given coherent archaeofauna trends and radiocarbon chronologies (n = 8 and 2 eggshell calcite radiocarbon ages at Toé and Kria, respectively) with respect to depth, the variable A/I values are not explicable in terms of mixing. Rather, the variability is most likely due to exposure of the eggshells to the high temperatures of campfires. Despite the variability, eggshells with relatively low A/I values amongst specimens recovered from similar depths (and therefore presumably least influenced by high temperatures) exhibit a gradual increase in A/I with respect to depth, as expected in a stratified deposit. From this observation it is suggested that the identification of heated eggshells will increase confidence in geochronological information provided by A/I. These studies illustrate the complications that arise from campfire-induced acceleration of amino acid racemisation and emphasise that although this phenomenon is common, it is not universally encountered in archaeological contexts.     

The design of effective and efficient trial trenching strategies for discovering archaeological sites

This paper reports a study on the effectivity and efficiency of trial trenching strategies for site discovery within the context of Dutch archaeological heritage management. It discusses the principles of site discovery by means of trial trenching, and suggests the optimal strategies for trial trenching survey, based on the results of simulations. Effective and efficient strategies for discovering different groups of archaeological sites are given, according to their presumed size, shape and feature density. The recommended strategies will be included in the Quality Norm for Dutch archaeology.     

Arctic archaeological sites threatened by climate change: A regional multi-threat assessment of sites in south-west Greenland

Climate change threatens many well-preserved archaeological sites in the Arctic. The paper presents the first Arctic multi-threat assessment focusing on the Nuuk region of Greenland. The results suggest that the majority of the 336 known archaeological sites are already exposed to impacts from microbial degradation, permafrost thaw and vegetation, and that these impacts will increase over the next 80 years. Additional impacts from coastal erosion are only noted at a limited number of sites due to a predominant consolidated and uplifting coast. The applied methods represent an important first step to identify threatened sites and emphasize important data limitations.     

Counting your chickens: density and distribution of chicken remains in archaeological sites of Oceania

In an effort to document the density and distribution of prehistoric chicken (Gallus gallus) remains across Oceania, this paper presents the analysis of reported faunal remains from over 500 individual archaeological and natural sites from across the Pacific. We examined the presence and absence of chicken in secure prehistoric contexts and factors which may account for this, including human choice, taphonomy, the influence of other animals on extinction events, differential access to resources, and purposeful extirpation. This research highlights the need for full study of the large percentage (18%) of Pacific avifauna collections which have yet to be analysed, to clarify the range and importance of chicken in prehistory. Copyright © 2008 John Wiley & Sons, Ltd.     

Taphonomy and dispersion of bones scavenged by New World vultures and caracaras in Northwestern Patagonia: implications for the formation of archaeological sites

Scavenger birds can feed on large- to small-sized vertebrates and may contribute in the formation of archaeological sites. To evaluate the modifications and dispersal patterns of bones produced by New World vulture and caracara from Northwestern Patagonia, samples of adult sheep, young sheep, and hare carcasses were offered and subsequently analyzed. New World vultures and caracaras quickly fed on the samples. Taphonomic and bone dispersal patterns suggest two types of accumulations: (1) open-air sites with large and medium-sized vertebrates represented by complete, fractured, scratched, notched, and punctured elements and (2) rock shelter or cave sites dominated by small vertebrates represented by broken, corroded, fractured, and digested elements.     

The growth of antinuclearism in New Zealand

This paper explores the transformation of antinuclear opinion in New Zealand into a more durable and structured political orientation. Antinuclear opinion first gripped a large portion of the New Zealand public after that nation's government banned the entry of United States nuclear warships in 1984. At that time, the public rallied behind the government's action. This consolidation effect, however, showed signs of being impermanent by 1986; antinuclear opinion appeared to be on the wane. Surprisingly, by 1989 this sentiment had finned into a more structured attitude, regardless of the fact that the government responsible for the nuclear ships ban had become very unpopular. The youthful cast to antinuclearism in New Zealand suggests that this orientation is in the process of becoming a fixture of that country's political culture. Political socialisation experiences best explain the continuation and growth of this orientation. The database used in this study comes from a series of national surveys—the most pertinent of which are polls conducted in 1985 and 1989.     

被动采样在考古发掘现场大气监测中的应用

通过对被动采样器结构和原理的分析,对其在环境监测中的应用情况进行综述。论述其对环境的适用性和考古发掘现场的特点及有害气体的监测需求。认为被动采样技术在考古发掘现场有害气体的监测中具有广泛的应用前景。