Balanced cross-section construction from seismic sections in areas of extensional tectonics

The application of the technique of balanced section construction, initially developed for areas of compressional folding and faulting, is reviewed with reference to extensional tectonics. A number of examples are discussed where these techniques have been successfully applied in the North Sea. The interpretation of geoseismic sections is considered to be greatly assisted by careful application of geometrical balance and a consideration of strain even in areas of low crustal extensions. The nature of seismic sections, however, places limitations on the validity of balancing which must be borne in mind with such interpretations and wherever possible the balancing of a geoseismic section should be confirmed by complete depth conversion. The rapid testing of the integrity of the geoseismic section by attempting to balance the section at the interpretational phase can eliminate many problems as well as allowing the fullest use to be made of the geophysical information.     

Evolution of Micropterigidae (Lepidoptera) in the SW Pacific

The distribution and possible evolutionary history of two major lineages of Micropterigidae in Australia, New Caledonia and New Zealand are presented. In Australia a simple vicariant evolutionary model is applied to the data and it is noted that the development of micropterigids is paralleled by the evolutionary history of eastern Australian rainforests. In New Zealand there appear to be distinct patterns of evolution in the different micropterigid lineages, a situation which is interpreted in terms of separate evolutionary histories, possibly on different land masses. In New Caledonia a species swarm exists which is also interpreted in terms of a former more complex geography. It is concluded that micropterigid evolution in the SW Pacific supports the idea of a composite origin for both New Zealand and New Caledonia.

     

Monitoring coastal morphology: the potential of low-cost fixed array action cameras for 3D reconstruction

The combination of structure-from-motion with multi-view stereo (SfM-MVS) photogrammetry has become an increasingly popular method for the monitoring and three-dimensional (3D) reconstruction of coastal environments. Climate change is driving the potential for increased coastal landward retreat meaning geomorphological monitoring using methods such as SfM-MVS has become essential for detecting and tracking impacts. SfM-MVS has been well-researched with a variety of platforms and spatial and temporal resolutions using mainly rectilinear digital cameras in coastal settings. However, there has been no assessment of the potential of fixed multi-camera arrays to monitor landward retreat or on the significance of camera placement in relation to the scene. This study presents an innovative method of image acquisition using a purpose-built camera grid and GoPro© action camera to evaluate the combined effects of camera height, obliqueness and overlap at a site of known landward retreat. This approach examines the effect of camera placement on scene reconstruction to aid the design of a multi-camera array. SfM-MVS dense point clouds display millimetre accuracy when compared to equivalent terrestrial laser scans and strong image network geometry with internal precision estimates of < 3 mm. Comparable point cloud reconstruction can be achieved with a small number of images stationed in appropriate positions. Initial results show as few as five images positioned at a cliff to camera ratio of 3:4.18 and camera obliqueness of 40° can provide reconstruction in the range of millimetres (mean error of 4.79 mm). These findings illustrate the importance of camera placement when using multiple cameras and aid the design of a low-cost, fixed multi-camera array for use at sites of small-scale landward retreat. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd     

Maintenance of Near-Surface Stratification in Doubtful Sound, a New Zealand Fjord

The surface waters of Doubtful Sound, a glacially carved fjord in south-western New Zealand, feature a quasi-permanent low-salinity-layer (LSL). The LSL is maintained year round by the extreme precipitation in the catchment (7 m yr⁻¹) and discharge from a hydroelectric power station (450 m³ s⁻¹). The robust, stable LSL has been shown to play a major role in controlling intertidal and subtidal community structure. By contrast, little is known about the dynamics of the LSL itself. The work presented here elucidates the response of the LSL to perturbations in the wind stress and rainfall.Frequency-domain analysis of salinity data collected from an array of moored instruments revealed that the LSL responded to perturbations in both the winds and rainfall. However, the specific roles of the wind stress and rain could not be adequately resolved in these analyses. By contrast, simulations of the response of the LSL using a three-dimensional primitive equation model revealed that strong up-fjord directed wind events set up a storm surge at the head of the fjord. This surge significantly deepens the LSL at the head of the fjord and retards or reverses estuarine circulation. The subsequent relaxation of the surge after the abatement of the wind stress resulted in a redistribution of buoyancy throughout the fjord over a two-day period. It is shown that the development and relaxation of the storm surge is a major process controlling the maintenance of the near-surface stratification.     

XXIst International Congress of Photogrammetry and Remote Sensing

The XXIst International Congress of Photogrammetry and Remote Sensing was held at the Beijing International Convention Centre, China, from 3rd to 11th July 2008. Reports are given on the Congress as a whole, including the General Assembly, some Technical Commission activities and the Congress Exhibition. Papers from the Congress are published in Volume XXXVII of the International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences.     

Understanding Place as ‘Home’ and ‘Away’ through Practices of Bird-watching

Bird-watching is an increasingly popular leisure activity. Previous research has taken for granted the identity of people who watch birds, often categorised by their level of skilled practice as ‘dude’, ‘birder’ or ‘twitcher’. Feminist geographers encourage us to explore identity work as an outcome of the reciprocal relationships between practices and place. Our feminist approach illustrates that the practices of bird-watching are always much more than categorising birds as species. This paper illustrates how the practices of bird-watching are integral to the making and remaking of sense of place as ‘home’ and ‘away’, to sustain identities beyond accepted categories of ‘dude’, ‘birder’ and ‘twitcher’. The creation and application of different types of ‘bird-lists’ helps to explain the ways in which practices of bird-watching facilitate making sense of place as simultaneously ‘home’, ‘away’ and habitat, as well as the identity work of home-maker, citizen-scientist and tourist. Our insights into these leisure practices of bird-watching are drawn from analysis of data gathered from 21 people who actively bird-watch and reside on the South Coast, New South Wales, Australia by combining research methods of talking, walking, drawing and photography.