Formation of beach‐ridge plains: an appreciation of the contribution by Jack L. Davies

A robust debate among coastal geomorphologists as to the processes by which beach‐ridge plains around Australia have formed was initiated by a former President of the Institute of Australian Geographers. This review gives special consideration to the work of Jack L. Davies, whose academic contributions to coastal geomorphology in Australia have not always been appropriately acknowledged when explaining how similar plains have evolved elsewhere in the world. Davies recognised that relatively steep storm waves caused erosion (cut) on beaches, whereas less steep long‐period swell waves returned sand (fill). He considered the beach berm to be the nucleus on which a beach ridge formed, which could subsequently develop into a foredune, in contrast to cobble ridges that were deposited during storms. Offshore conditions regulate supply of sand to the shoreline, partly through effects on wave refraction, with higher rates of supply where the nearshore is shallow. It was apparent to Davies that the elevation of successive ridges might, but not necessarily, provide evidence of past changes of sea level, despite adornment by variable amounts of windblown dune sand. Morphodynamic understanding of long‐term coastal evolution, based on radiocarbon dating chronologies, has demonstrated that Australian coastal plains formed over the past ~6,000 years when sea level has been close to its present level, in contrast to several documented locations in the northern hemisphere where the sea has been rising for the past few millennia. Particularly insightful were observations by Davies that ridge formation could be influenced by a range of factors including changes in sea level, storminess, or sediment supply. These factors acting singly or in combination seem likely to change in the future. Understanding such responses remains a high priority and can be addressed by new technologies, such as light detection and ranging, optically stimulated luminescence dating, ground‐penetrating radar, and computer simulation.     

Magnetic Gradient Survey of the Marpole Period Dionisio Point (DgRv-003) Plankhouse Village,Northwest Coast of North America

Architectural reconstructions of plankhouses are central to the study of household and community organization on the Northwest Coast of North America. However, the sample of substantially excavated houses is constrained by their size, stratigraphic complexity, and typically limited surface expression. We present the results of a magnetic gradiometry survey of the Dionisio Point site (DgRv-003) village, occupied ca. a.d. 500–700 on the coast of British Columbia, Canada. Survey of four house platforms reveals patterning of magnetic anomalies consistent with the structure of shed-roof houses, a design recorded ethnographically and identified archaeologically at the site. These results suggest a consistent pattern of spatial and, potentially, social organization of the households. The similarity of patterns suggests that magnetometry may be useful for guiding plankhouse excavations elsewhere on the Northwest Coast, providing a means for expanding our knowledge of houses without relying solely on traditional excavation methods.     

Assessing Quality of Spatial Models Using the Structural Similarity Index and Posterior Predictive Checks

Model assessment is one of the most important aspects of statistical analysis. In geographical analysis, models represent spatial processes, where variability in mapped output results from uncertainty in parameter estimates. Slight spatial misalignments can cause inflated error scores when comparing maps of observed and predicted variables using traditional error metrics at the level of individual spatial units. We conceptualize spatial model assessment as a continuous value map comparison problem and employ methods from image analysis to score model outputs. The structural similarity index, a measure that attempts to replicate the human visual system using a local region approach, is used as an exploratory map comparison statistic. The measure is implemented within a Bayesian spatial modeling framework as a discrepancy measure in a posterior predictive check of model fit. Results are reported for simulation studies representing a variety of spatial processes in a spatial and space–time context. A case study of rainfall mapping in Sri Lanka demonstrates the proposed methodology applied to assessment of Bayesian kriging interpolations. Both simulation studies as well as the case study demonstrate that the approach reveals hidden spatial structure not uncovered by traditional methods. The spatially sensitive assessment methodology provides a diagnostic tool to support spatial modeling and analysis. La evaluación de modelos es uno de los aspectos más importantes de análisis estadístico. En el análisis geográfico, los modelos representan procesos espaciales en los que la variabilidad en los outputs es el resultado de la incertidumbre en los parámetros estimados. Leves desajustes espaciales pueden inflar los valores de error en la comparación entre los mapas de las observaciones y los mapas de las predicciones de las variables si es que se usan medidas tradicionales de medición de error al nivel de unidades espaciales individuales. Los autores conceptualizan la evaluación de modelos espaciales como un problema de comparación mapas de valor continuo y emplea métodos de análisis de imágenes para cuantificar los resultados del modelo. Se utiliza el índice de similitud estructural (SSIM), una medida que intenta replicar el sistema visual humano utilizando un enfoque de región local, como técnica de exploratoria comparación estadística de mapas. El índice es implementado dentro de un marco de modelización espacial bayesiano como medida de discrepancia en la comprobación posterior de predicción del desempeño del modelo. Los resultados se presentan para varios casos de simulación que representan una serie de procesos espaciales en un contexto espacio‐temporal y espacial. Un estudio de caso de mapeo de lluvias en Sri Lanka sirve como demostración de la metodología propuesta y su aplicación a la evaluación de las interpolaciones tipo krigeage (kriging) bayesianas. Tanto los estudios de simulación, así como el estudio de caso demuestran que el enfoque propuesto revela la estructura espacial oculta no evidenciada por métodos tradicionales. La metodología de evaluación espacialmente sensible que se presenta en este artículo proporciona una herramienta de diagnóstico para apoyar la elaboración de modelos y análisis espacial. 模型评估是统计分析中最为重要的内容之一。在地理分析中用模型表达空间过程,参数估计的不确定性会导致地图输出结果的可变性。当采用传统误差指标度量,在个体空间单位水平上进行观测和预测变量的地图比较时,微小的空间错位就可能导致误差的倍增。为此,本文通过将空间模型评估指标概念化为一个连续值图比较问题,并利用图像分析方法来评定模型输出。一种尝试以局域方法仿制人类视觉系统的度量指标——结构相似指数(SSIM),被用作为探索性地图的比较统计量。在贝叶斯空间模型框架下实现其量算,并将其作为一个偏差度量应用于模型拟合的后预测校验。仿真研究的结果显示出空间及时空环境下多类空间过程。以斯里兰卡降雨过程图为案例,展示了上述方法对贝叶斯克里格插值的准确性评估。仿真研究与实证结果均证明本文提出的方法可揭示以往传统方法掩盖的空间结构特征,空间敏感性评价为本研究的空间建模和分析提供了一个诊断工具。     

Changing patterns of carnivore modification in a landscape bone assemblage, Amboseli Park, Kenya

This study compares the landscape-scale taphonomic signal of carnivore modification to the surficial bone assemblage in Amboseli Park, Kenya as it was in 1975 and 2002–2004. Change in predator abundances over time provides a means of assessing the taphonomic signal of carnivore-mediated bone consumption and destruction under differing ecological conditions and varying levels of conspecific competition for resources. The landscape assemblage indicates taxonomic variation in the patterning of carnivore modification to ungulates of different size classes as well as within equivalent size classes. Analyses of long bone elements indicate that the differential destruction of limb ends and the strength of the correlation between limb end abundance and bone mineral density provide an indication of the intensity of carnivore modification to a faunal assemblage. The ability to infer levels of carnivore modification based on limb elements can provide faunal analysts with the tools to determine whether the taphonomic signals in the fossil record relate to carnivore modification, hominin transport of appendicular elements, or both.     

An Iron Bastard Minion Drake Extraordinary by John Browne from the Pinnace Swan (1641–53)

A small iron gun recovered from the wreck of the Caroline warship Swan has been identified as a drake, a lightweight tapered-chamber design dating from the 1620s. It is the only known cast-iron example of such a piece made by John Browne, gunfounder to Charles I, who was the leading figure in its development and manufacture in England. The gun was found together with an associated carriage, port-lid, and case shot appropriate to its calibre.
© 2004 The Nautical Archaeology Society     

Geographical Imaginations and Spaces of Political Engagement: Examples from the Indian Alliance

This paper is concerned with the various ways in which geographical imaginations are inflected in politics. It draws on examples from a three‐way partnership of civil society organisations based in Mumbai, India. This movement seeks to reconfigure the governance of anti‐poverty strategies by placing "poor people" at the centre of its activities. The partnership, which refers to itself as the Alliance , is involved in the mobilisation and creation of a range of alternative geographical imaginations that are inflected in the production of new spaces of political engagement. By exploring two of the Alliance's strategies—enumerations and exhibitions—I will illustrate some of the ways in which these alternative geographical imaginations feature in the creation of spaces of political engagement. These strategies involve the practical demonstration of the capacities of the poor to donors and states, and reflect a particular conception of the poor and social change.
The spaces of political engagement formed in part through the Alliance's work depend significantly on a commitment to non‐party alignment, an approach that has received criticism from NGOs and commentators involved with urban poverty. I will argue that the Alliance represents a broad development alternative—rather than a form of alternative development—which nonetheless is making substantial progress in the politics of citizenship in Mumbai.