Recent Improvements to IERS Bulletin A Combination and Prediction

Driven by a need for increased accuracy in real-time Earth orientation parameters (EOPs), the Bulletin A (Rapid Servce and Predictions) of the International Earth Rotation Service (IERS) has recently made several major changes to its combination and prediction procedures. Changes to the process ob combining multi-technique results include creation of a daily Bulletin A updata, inclusion of several new data sets, and use of polar motion rantes for the latest epoch. Notably, the contributions from GPS observations have grown steadily in significance, both for polar motion and Universal Time (UT1). The prediction procedure has, in turn, benefited from these changes as well as improvements to the polar motion prediction model. As a result, demanding real-time applications, such as for satellite orbit extrapolations should observe a major improvement in the accuracy of our real-time EOP products. All results, together with supporting and diagnostic information, are available at the website http://maia.usno.navy.mil. The maximum EOP errors (root-mean-squared sense) that a real-time user would experience using the latest available update of Bulletin A are currently estimated to be ∼0.9 milliarcseconds (mas) for polar motion and ∼0.15 milliseconds (ms) for UT1-UTC. The data latency (the lag since the most recent observations) for EOP predictions need not exceed ∼41 hours for users who avail themselves of the daily updates. Over the past four years, the accuracy for real-time applications has improved by nearly a factor of 4 in polar motion and a factor of 10 in UT1. This is primarily due to the large reduction in data latency, which in turn is mostly possible due to the Rapid product delivery of the International GPS Service (IGS) (see Mireault et al, 1999). ? 2001 John Wiley & Sons, Inc.     

Measuring Flume Surfaces for Hydraulics Research Using a Kodak DCS460

A critical problem in hydraulics research is accurate measurement of fluvially worked sediments, both in the field and in scaled representations of field situations in laboratory flumes. Such measurement must provide information on individual grain characteristics, and their organisation into structures referred to as bedforms. Existing measurement approaches are based upon mechanical or laser profiling devices, which are both expensive and take considerable time to acquire data, particularly where information is required at very high densities. This paper demonstrates how conventional automated terrain model extraction software, combined with image acquisition using a Kodak DCS460 digital camera, has been effective in generating digital elevation models of complex bed morphology. This has reduced time spent collecting data in the flume and has allowed data collection at much higher spatial and temporal densities. Application of the method is illustrated by research carried out at Hydraulics Research Wallingford. Issues discussed include configuration of photographs and control coordinates; appropriate camera calibration methods; stability of inner orientation of the Kodak DCS460; and accuracies obtained. Comparisons with independent check data reveal that accuracies of ±2.5mm have been achieved using a camera-to-object distance of 4.2 m.     

Shaping and Sharing Responsibility: Social Memory and Social Learning in the Australian Rural Bushfire Landscape

Responding to increased frequency and severity of bushfires, Australian governments called for “shared responsibility” for bushfire preparation and mitigation. This requires engagement between all sectors of community—government agencies, businesses, not-for-profit, and residents. Fire management agencies remain concerned about whether all communities in fire-prone landscapes are equally equipped to participate in sharing responsibility. A related question is how experience of bushfire influences subsequent community fire management practices. This paper addresses social learning and social memory in a landscape that has experienced repeat bushfires between 2006 and 2013. It examines the relationships between memory, learning and practice among a farming community in western Victoria and government agencies with bushfire management responsibility. Findings suggest that social learning and social memory interact and new practices emerge as the participants embrace “shared responsibility.” However, ambiguities remain about “what” is being shared and what being “responsible” means at different points in preparation and response.     

Spatiality,Maps, and Mathematics in Critical Human Geography: Toward a Repetition with Difference

Quantitative and cartographic methods are today often associated with absolute, Newtonian conceptions of space. We argue that some such methods have not always been and need not be so allied. Present geographic approaches to relational space have been largely advanced through radical political economic and feminist thought. Yet we identify quantitative and cartographic methods (taking as exemplars a range of thinkers, some of whom were most prominent in the 1960s and 1970s) that can contribute to these approaches to relational space. We suggest neglected methods to revisit, new alliances to be forged with critical human geography and cultural critique, and possible paths to enliven geographical imaginations.     

Harnessing the power of immersive virtual reality - visualization and analysis of 3D earth science data sets

ABSTRACT

The availability and quantity of remotely sensed and terrestrial geospatial data sets are on the rise. Historically, these data sets have been analyzed and quarried on 2D desktop computers; however, immersive technologies and specifically immersive virtual reality (iVR) allow for the integration, visualization, analysis, and exploration of these 3D geospatial data sets. iVR can deliver remote and large-scale geospatial data sets to the laboratory, providing embodied experiences of field sites across the earth and beyond. We describe a workflow for the ingestion of geospatial data sets and the development of an iVR workbench, and present the application of these for an experience of Iceland’s Thrihnukar volcano where we: (1) combined satellite imagery with terrain elevation data to create a basic reconstruction of the physical site; (2) used terrestrial LiDAR data to provide a geo-referenced point cloud model of the magmatic-volcanic system, as well as the LiDAR intensity values for the identification of rock types; and (3) used Structure-from-Motion (SfM) to construct a photorealistic point cloud of the inside volcano. The workbench provides tools for the direct manipulation of the georeferenced data sets, including scaling, rotation, and translation, and a suite of geometric measurement tools, including length, area, and volume. Future developments will be inspired by an ongoing user study that formally evaluates the workbench’s mature components in the context of fieldwork and analyses activities.     

Working in a Landscape of Recession and Expansion: Academic Jobs in Geography in the United States, 1990–2011

The recent economic recession brought much university hiring to a standstill in the United States. Geography, in spite of strong prerecession growth, was no exception. Without a sense of how the academic geography job market has changed over the past decades, however, it is difficult to assess any recession-related decline or the relative strength of any recovery. This article presents an analysis of academic job postings in the field of geography from 1990 through 2011. Using data aggregated from the AAG Newsletter, which acts as an informal clearinghouse for most academic openings for geographers at four-year colleges and universities in the United States, we assess changes in the overall magnitude in numbers of academic job openings, with the particular goal of placing the recession-based paucity of openings within its broader historical context. Our results indicate that, indeed, the recession led to a very sharp decline in advertisements, but compared to previous recessions, the recovery appears to have occurred very quickly. Open-rank and temporary/non-tenure-track positions appear to have been fairly robust to the poor economic conditions, whereas assistant professor openings were particularly hard hit.     

Influence of groundwater pumping on streamflow restoration following upstream dam removal

We compared streamflow in basins under the combined impacts of an upland dam and groundwater pumping withdrawals, by examining streamflow in the presence and absence of each impact. As a qualitative analysis, inter‐watershed streamflow comparisons were performed for several rivers flowing into the east side of the Central Valley, CA. Results suggest that, in the absence of upland dams supporting large reservoirs, some reaches of these rivers might develop ephemeral streamflow in late summer. As a quantitative analysis, we conducted a series of streamflow/groundwater simulations (using MODFLOW‐2000 plus the streamflow routing package, SFR1) for a representative hypothetical watershed, with an upland dam and groundwater pumping in the downstream basin, under humid, semi‐arid, and arid conditions. As a result of including the impact of groundwater pumping, post‐dam removal simulated streamflow was significantly less than natural streamflow. The model predicts extensive ephemeral conditions in the basin during September for both the arid and semi‐arid cases. The model predicts continued perennial conditions in the humid case, but spatially weighted, average streamflow of only 71% of natural September streamflow, as a result of continued pumping after dam removal. Published in 2006 by John Wiley & Sons, Ltd.