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Low-altitude aerial thermography for the archaeological investigation of arctic landscapes

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Abstract

Remotely-piloted aircraft (RPA) thermography is one of the least utilized remote-sensing methods in archaeology, yet it has great potential for visualizing subsurface archaeological features. Given the logistic constraints of remote fieldwork, arctic archaeologists have much to gain from this portable and effective remote-sensing application. This paper presents a novel methodological approach for the collection, processing, and analysis of RPA thermal imagery in the Canadian High Arctic that accounts for the unique environmental and logistic challenges of RPA applications in polar regions. The development of this approach is based on a case study of two Pre-Inuit (4500-1000 B.P.) archaeological sites from the Foxe Basin region, Nunavut. The presented workflow demonstrates the effectiveness of RPA ther-mography in archaeological feature detection in an Arctic-tundra setting. Thermal detection of several previously unidentified subsurface features in Foxe Basin suggest that surface feature visibility is lower than previously anticipated, calling attention to potential judgemental biases in pedestrian archaeological surveys in Arctic contexts. Based on the utility of low-altitude thermography for visualizing the internal structures of Tuniit dwellings, this paper proposes that thermography facilitates archaeological spatial analysis beyond feature prospection. RPA thermography is a non-destructive and economic remote-sensing solution to some of the persistent logistic challenges to fieldwork in remote locations that often inhibit large-scale archaeological analyses not only in the Canadian Arctic, but remote Arctic-Alpine regions worldwide.

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Conference Paper
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Thesis
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The study of historical field boundaries is based at first on the documentary evidence, but in the case of Lion-en-3eauce township there is no thing older thorn cje 1 808 land- register. But thermal prospection brings up useful information showing the headland ridges caracterised by the association of a warm strip and of cold strip (those ridges were controled by altmetric measurment on the field) ; other old limits appear which correspond to ancient ditches. The date of these boundaries can be shown by excavation of certain ones and of the sites located by surface remains, which allow a relative chronology to be obtain.
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Le present article propose une approche methodologique concernant l'etude des foyers en general. Les foyers de la tradition paleoesquimaude sont souvent assez bien conserves, ce qui permet d'interpreter les processus de combustion utilises et comment ces derniers affectaient le climat a l'interieur de l'habitation. Pour obtenir ces informations, il est important de recueillir des donnees concernant les pierres fracturees par le feu. Les Paleoesquimaux utilisaient une pyro-technologie versatile, s'ajustant aux conditions les plus extremes dans des regions ou l'acces au bois de chauffage etait limite. Une reconstitution experimentale combinee a des calculs de la combustion hypothetique des matieres grasses demontre qu'il etait possible pour les Independanciens I de l'Arctique septentrional de passer confortablement l'hiver dans des tentes. Enfin, les aspects symboliques des foyers sont abordes dans le texte.
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Dans la region du cercle polaire arctique, archeologues et gestionnaires du patrimoine sont de plus en plus preoccupes par la destruction des sites archeologiques due aux changements climatiques actuels. Cet article presente le projet Arctic CHAR cree pour resoudre ce probleme dans la region du delta de la riviere Mackenzie, dans le nord-ouest canadien. Plusieurs sites cotiers temoignent de l’histoire des Inuvialuit qui peuplent le delta du Mackenzie. En raison de la fonte du pergelisol et de la hausse du niveau marin relatif, ces sites sont detruits a une vitesse alarmante. Le projet Arctic CHAR se developpe sur deux axes principaux : des sondages pour evaluer l’etat des ressources patrimoniales a travers la region et la fouille des sites menaces les plus importants.
Chapter
UAV-borne thermal imaging involves the determination of ground surface temperature from thermal infrared measurements deploying an unmanned airborne vehicle (UAV). A large variety of UAVs is available and applied for different military and civil tasks. UAV-borne thermal imaging provides spatially distributed information of the ground surface temperature. In contrast to satellite or ground based measurement, the usage of a UAV allows us to obtain spatially distributed and geometrically highly resolved information on the ground surface temperature without the need to access the ground. The area can be flat or hilly, and steep walls and hillsides can be investigated easily. However, some problems, especially tasks related to mosaicking of the images, are not fully resolved to date. We address the detection of the anomalies in ground surface temperature induced by underground burning coal seams as example and describe the challenges and opportunities of UAV-borne thermal imaging, based on our experiences in this field.
Article
Cet article presente une synthese des vestiges architecturaux paleoesquimaux du Bas Arctique central canadien. Les Paleoesquimaux habiterent cette region pendant environ 4 000 ans decoupes par les archeologues en neuf periodes chrono-culturelles: le Paleoesquimau ancien (Predorsetien, Transition predorsetienne/dorsetienne, Lagoon et Groswaterien) et le Paleoesquimau recent (Dorsetien ancien, moyen, recent et terminal, ainsi que le Choris). Bien que la validite de ces divisions reste contentieuse, les recherches dans cette region ont documente une importante variabilite architecturale parmis ces groupes culturels. Cet article propose un systeme typologique decrivant et organisant les vestiges architecturaux signales jusqu'a ce jour afin de susciter de nouvelles discussions concernant les causes de la variabilite architecturale paleoesquimaude.
Article
Discusses, on basis of studies in northern Alaska, soil forming processes in arctic regions and considers the relation between vegetation and soils and problems of classification and mapping. Tundra soils are poorly drained, mineral in nature, and underlain by permafrost at depths of 1-2 ft Arctic brown soils form under free drainage, are mineral in character, and confined to ridges, terrace edges, and stabilized dunes. The active layer in such soils is usually deep. Downslope movement and frost action tend to disrupt any orderly morphology in both wet and well-drained sites. Moisture conditions in arctic soils exert a marked selective influence on vegetation.--from SIPRE.
Article
Aerial thermograms of an area in north-central Arizona immediately to the north of Merriam Crater have revealed the existence of parallel arrays of alternating ridge and swale linear features in the ashfall zone of Sunset Crater. The patterns are not easily identified on simultaneously acquired panchromatic photographs. Pollen and soil analyses confirm the highly geometric pattern to be a previously unrecognized prehistoric agricultural field. Recovery of Sinagua sherds of known age found at nearby living sites and in the field indicates that the farming activity occurred between A.D. 1065 and 1250. After 700 years of abandonment, local plant succession for the field has not yet fully re-established the probable former shrub community, apparently due to differences in physical and chemical properties existing between field and nonfield soil areas, related perhaps to prehistoric agricultural practices.
Article
This paper discusses challenges facing archaeologists and archaeology remains at the “Tops of the World,” the Arctic, Subarctic, and Subantarctic regions of the globe, in light of climate change and human activities. One set of challenges includes climate change with rising sea levels, flood levels, decreasing permafrost, wind erosion, and tree re-growth. Another set includes increasing demographic and economic expansion with concurrent pollution, oil and mineral exploitation, and development of hydroelectricity, aquaculture, and tourism in the regions. The real and probable impacts and consequences of those factors on the archaeology—both generally and regionally—at the Tops of the World are outlined, leading to a discussion of how long-term research, cultural resource management, and educational strategies can be developed to deal with them.
Article
This paper presents the first detailed record of Paleoeskimo occupation history of Foxe Basin, Nunavut, Arctic Canada, the traditional Paleoeskimo “core area.” Rather than continuous, stable occupations from approximately 4000–1000 B.P. traditionally assumed for the core area, the region has undergone a series of demographic oscillations, including several instances of abandonment of key areas, most notably Igloolik. The Foxe Basin demographic trends are reminiscent of Paleoeskimo “boom and bust” cycles recognized elsewhere, but show no consistent chronological pattern either within Foxe Basin or inter-regionally. Equally important, our results bear on the critical question of the Pre-Dorset to Dorset transition. Rather than having been a gradual in situ process centered within the core area, the demographic patterns, including the abrupt and widespread appearance of semi-subterranean dwellings during earliest Dorset, are consistent with newly arrived populations from outside of Foxe Basin. While there is no obvious “parent” culture to Dorset within the Eastern Arctic, it is suggested that a Western Arctic origin, specifically Norton Culture, invoking to some extent Jorgen Meldgaard's “smell of the forest”, may have played a significant role.
Article
This thesis is a study of economic change in the Palaeoeskimo period (3200 B. P. to 1000 B. P.) at Igloolik Island, in the Foxe Basin, eastern Canadian Arctic. Evidence derived from the analysis of settlement, zooarchaeological and artefactual data was used to infer changes in settlement, subsistence and social organization between early PreDorset (3200 B. P.) and Late Dorset (1000 B. P.). The primary economic unit during early PreDorset was probably the nuclear family and at Igloolik the major subsistence activity was ringed seal hunting. PreDorset settlement was short-term and groups appear to have been highly mobile, moving away from Igloolik to exploit other resources on a seasonal basis. In contrast Dorset groups were less mobile, spending a greater proportion of the year at Igloolik and exploiting a wider range of resources. The Early Dorset period was characterized by the development of new technology, communal walrus hunting, storage practices and the appearance of larger economic and social units. In Late Dorset, this basic pattern remained the same, although subsistence strategies continued to broaden. The development of communal walrus hunting, storage and the widening of the subsistence base combined to produce relative subsistence security in Dorset as compared to PreDorset. This relative security seems to have been expressed in the elaboration of material culture, particularly walrus hunting harpoon heads, and it may have resulted some socio-economic differentiation between Dorset groups in the Foxe Basin region and those in the central and high Arctic.
Article
Arctic terrestrial ecosystems subjected to anthropogenic disturbance return to their original state only slowly, if at all. Investigations of abandoned settlements on three islands in the eastern Canadian Arctic Archipelago have detected striking similarities among contemporary and ancient human settlements with regard to their effects on tundra vegetation and soils. Ordination procedures using 240 quadrats showed the plant assemblages of Thule (ca. 800 B.P.) winter dwellings on northern Devon and southern Cornwallis Islands to be floristically similar to pedestrian-trampled meadows on northeast Baffin Island last used ca. 1969. Comparisons from the literature made with other North American sites in the Low Arctic reveal similar findings. The implication is that the depauperate flora of the Arctic has a limited number of species able to respond to disturbance, and that anthropogenically disturbed patches may be extremely persistent.
Article
This study provides an assessment of changes in the occurrence frequency of four types of adverse-weather (freezing precipitation, blowing snow, fog, and low ceilings) and no-weather (i.e., no precipitation or visibility obscuration) events as observed at 15 Canadian Arctic stations of good hourly weather observations for 1953–2004. The frequency time series were subjected to a homogenization procedure prior to a logistic regression–based trend analysis. The results show that the frequency of freezing precipitation has increased almost everywhere across the Canadian Arctic since 1953. Rising air temperature in the region has probably resulted in more times that the temperature is suitable for freezing precipitation. On the contrary, the frequency of blowing snow occurrence has decreased significantly in the Canadian Arctic. The decline is most significant in spring. Changes in fog and low ceiling (LC) occurrences have similar patterns and are most (least) significant in summer (autumn). Decreases were identified for both types of events in the eastern region in all seasons. In the southwest, however, the fog frequency has increased significantly in all seasons, while the LC frequency has decreased significantly in spring and summer. The regional mean rate of change in the frequency of the four types of adverse weather was estimated to be 7%–13% per decade. The frequency of no-weather events has also decreased significantly at most of the 15 sites. The decrease is most significant and extensive in autumn. Comparison with the adverse-weather trends above indicates that the decline in no-weather occurrence (i.e., increase in weather occurrence) is not the result of an increase in blowing snow or fog occurrence; it is largely the result of the increasing frequency of freezing precipitation and, most likely, other types of precipitation as well. This is consistent with the reported increases in precipitation amount and more frequent cyclone activity in the lower Canadian Arctic.
Article
The results of measurements of net total radiation flux and tempera- tures in the air and surface layers of the tundra and snow near Barrow, Alaska, are presented for the period September 1965 to September 1966. Lowest average monthly temperatures occurred in March, the highest in July. The minimum aver- age net total radiation occurred in January with the maximum in July. The tundra surface began to thaw by 18 June and to freeze by September.
Article
This paper reviews hydrologie processes in the permafrost regions of northern North America. Much work has recently been done at spect$c experimental plots to parallel the progress in laboratory investigations, improving our understanding of the heat and water jluxes in thawed and froren grounds, injïltration in frozen soils, evaporation in a cold environment, interaction between snow and its frozen substrate, and the dynamics of storage in the active layer. Field research on permafrost slopes and in northern research basins adds to our knowledge of permafrost groundwater hydrology, runoff generating processes, river freeze-up and breakup processes and allows more precise definition of basin water balance. Sufficient hydrometric data are now available to analyse the streamflow charac- teristics in an area with permafrost, and more work should be done along this line. It is urged that process studies be continued to gain a better understanding of the effect of permafrost upon the hydrologie cycle. Further research is needed to predict the impacts of human activities on the movement and redistribution of water.
Article
Infrared thermography transforms the thermal energy, emitted by objects in the infrared band of the electromagnetic spectrum, into a visible image. This feature represents a great potentiality to be exploited in many fields, but this technique is still not adequately enclosed in industrial instrumentation because of a lack of adequate knowledge; at first sight, it seems too expensive and difficult to use. The aim of the present paper is to shortly overview existing work and to describe the most relevant experiences devoted to the use of infrared thermography in three main fields, i.e. thermo-fluid dynamics, technology and cultural heritage, which have been performed in the department the authors belong to. Results may be regarded from two points of view, either as validating infrared thermography as a full measurement instrument, or as presenting infrared thermography as a novel technique able to deal with several requirements, which are difficult to perform with other techniques. This study is also an attempt to give indications for a synergic use of the different thermographic methods and sharing experiences in the different fields.
Article
Interaction of archaeological features with the secular variation in surface heat flux generates an anomalous ground temperature distribution which can form the basis for a shallow geophysical prospecting tool. Earlier studies have concentrated on recording surface temperature disturbances via aerial thermography but these results can be biased towards minor variations in vegetation, albedo. and microclimate. A more promising approach is to record temperatures at a depth of 20cm using a simple probe. Anomalies at this depth arise from the interaction of objects with the annual heat-flux cycle and other long-term temperature variations. The amplitude, shape, and phase of anomalies have been modelled, together with the nature and magnitude of other, unwanted causes of ground temperature variation. Field equipment and data processing techniques for the direct-contact approach to thermal prospection have undergone trails in the U.K. at Verulamium and Fountains Abbey.