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51.
This article considers the concept and significance of transformative research in the context of geography education. It provides an overview of how the capacity-building activities and management operations of a research coordination network (RCN) are designed to support broad-scale advances in geography education theory, methods, and practice. Vignettes of RCN activities are presented as examples of pathways toward transformative research in the areas of geography learning progressions, assessments of spatial thinking, and geospatially enabled project-based learning. Beyond the prospect of introducing new paradigms of learning and using research findings to inform and systematically change approaches to teacher education and curriculum development, an RCN offers an opportunity to plan broad-based strategy and develop leadership needed to address many long-standing challenges that have undermined the quality and quantity of geography education research. These challenges include the low visibility of geography education research relative to other geographic subdomains, the difficulty of carrying out interdisciplinary and international research collaborations, low rates of transfer and uptake of research findings in practitioner communities and in policymaking, and the erosion of graduate-level programs that prepare students to plan and design conceptually rigorous educational research in geography. 相似文献
52.
53.
Annual deformation signals from homogeneously reprocessed VLBI and GPS height time series 总被引:3,自引:3,他引:0
Volker Tesmer Peter Steigenberger Markus Rothacher Johannes Boehm Barbara Meisel 《Journal of Geodesy》2009,83(10):973-988
The first part of this paper compares homogeneously reprocessed Very Long Baseline Interferometry (VLBI) and Global Positioning
System (GPS) long-term height series from 1994 to 2007. The data analysis used fully adapted state-of-the-art models (like
VMF1 and a priori zenith delays from ECMWF) for the GPS and VLBI processing. The series are compared in terms of long-term
non-linear behaviour, harmonic and mean annual signals (not necessarily of harmonic nature). The similarity between both techniques
is very good (especially the mean annual signals), which is assumed to be due to the adapted models and consistent reprocessing
of both series. As two almost independent observing techniques see the same annually recurring signals at almost all co-located
sites, we expect a good geophysical interpretability as integral vertical deformation. For the second part of this paper,
the height time series of 161 suitable GPS sites (of the same solution as before) are used to determine a harmonic and a mean
annual signal for each of them. Comparing the annual signals for this big dataset visually to GRACE-determined load deformations
described in other publications, we find good agreement. This puts emphasis to the assumption that our height data have a
lot of potential to be interpreted as geophysical signals. Out of these 161, 131 are grouped to 55 clusters, if at least two
nearby (some thousand kilometres) sites show similar mean annual signals, which are thus confirmed to be real regional deformation,
not local or technical artefacts. These 55 signals are presented on a “world map” of regional average mean annual height signals,
as easy-to-handle tool to validate geophysical models. The data of these measured regional mean annual signals can be downloaded
from a web-page for numerical analysis. 相似文献
54.
Forecast Vienna Mapping Functions 1 for real-time analysis of space geodetic observations 总被引:3,自引:2,他引:1
The Vienna Mapping Functions 1 (VMF1) as provided by the Institute of Geodesy and Geophysics (IGG) at the Vienna University
of Technology are the most accurate mapping functions for the troposphere delays that are available globally and for the entire
history of space geodetic observations. So far, the VMF1 coefficients have been released with a time delay of almost two days;
however, many scientific applications require their availability in near real-time, e.g. the Ultra Rapid solutions of the
International GNSS Service (IGS) or the analysis of the Intensive sessions of the International VLBI Service (IVS). Here we
present coefficients of the VMF1 as well as the hydrostatic and wet zenith delays that have been determined from forecasting
data of the European Centre for Medium-Range Weather Forecasts (ECMWF) and provided on global grids. The comparison with parameters
derived from ECMWF analysis data shows that the agreement is at the 1 mm level in terms of station height, and that the differences
are larger for the wet mapping functions than for the hydrostatic mapping functions and the hydrostatic zenith delays. These
new products (VMF1-FC and hydrostatic zenith delays from forecast data) can be used in real-time analysis of geodetic data
without significant loss of accuracy. 相似文献
55.
56.
Matt A. King Zuheir Altamimi Johannes Boehm Machiel Bos Rolf Dach Pedro Elosegui François Fund Manuel Hernández-Pajares David Lavallee Paulo Jorge Mendes Cerveira Nigel Penna Riccardo E. M. Riva Peter Steigenberger Tonie van Dam Luca Vittuari Simon Williams Pascal Willis 《Surveys in Geophysics》2010,31(5):465-507
The provision of accurate models of Glacial Isostatic Adjustment (GIA) is presently a priority need in climate studies, largely due to the potential of the Gravity Recovery and Climate Experiment (GRACE) data to be used to determine accurate and continent-wide assessments of ice mass change and hydrology. However, modelled GIA is uncertain due to insufficient constraints on our knowledge of past glacial changes and to large simplifications in the underlying Earth models. Consequently, we show differences between models that exceed several mm/year in terms of surface displacement for the two major ice sheets: Greenland and Antarctica. Geodetic measurements of surface displacement offer the potential for new constraints to be made on GIA models, especially when they are used to improve structural features of the Earth’s interior as to allow for a more realistic reconstruction of the glaciation history. We present the distribution of presently available campaign and continuous geodetic measurements in Greenland and Antarctica and summarise surface velocities published to date, showing substantial disagreement between techniques and GIA models alike. We review the current state-of-the-art in ground-based geodesy (GPS, VLBI, DORIS, SLR) in determining accurate and precise surface velocities. In particular, we focus on known areas of need in GPS observation level models and the terrestrial reference frame in order to advance geodetic observation precision/accuracy toward 0.1 mm/year and therefore further constrain models of GIA and subsequent present-day ice mass change estimates. 相似文献
57.
Numerical simulation of troposphere-induced errors in GPS-derived geodetic time series over Japan 总被引:2,自引:2,他引:0
Troposphere-induced errors in GPS-derived geodetic time series, namely, height and zenith total delays (ZTDs), over Japan
are quantitatively evaluated through the analyses of simulated GPS data using realistic cumulative tropospheric delays and
observed GPS data. The numerical simulations show that the use of a priori zenith hydrostatic delays (ZHDs) derived from the
European Centre for Medium-Range Weather Forecasts (ECMWF) numerical weather model data and gridded Vienna mapping function
1 (gridded VMF1) results in smaller spurious annual height errors and height repeatabilities (0.45 and 2.55 mm on average,
respectively) as compared to those derived from the global pressure and temperature (GPT) model and global mapping function
(GMF) (1.08 and 3.22 mm on average, respectively). On the other hand, the use of a priori ZHDs derived from the GPT and GMF
would be sufficient for applications involving ZTDs, given the current discrepancies between GPS-derived ZTDs and those derived
from numerical weather models. The numerical simulations reveal that the use of mapping functions constructed with fine-scale
numerical weather models will potentially improve height repeatabilities as compared to the gridded VMF1 (2.09 mm against
2.55 mm on average). However, they do not presently outperform the gridded VMF1 with the observed GPS data (6.52 mm against
6.50 mm on average). Finally, the commonly observed colored components in GPS-derived height time series are not primarily
the result of troposphere-induced errors, since they become white in numerical simulations with the proper choice of a priori
ZHDs and mapping functions. 相似文献
58.
R Daly CAK Daly RH Bennett PD Cowley MAM Pereira JD Filmalter 《African Journal of Marine Science》2018,40(3):315-321
The giant trevally Caranx ignobilis (Forsskål) is an important apex predatory fish typically associated with coral reef communities. It is prized in recreational and commercial fisheries, yet little is known about its aggregation dynamics and susceptibility to fishing pressure. This study reports on a previously undocumented aggregation of mature giant trevally observed over a period of eight years (2010–2017) at Ponta do Ouro Partial Marine Reserve in southern Mozambique. The aggregation is one of the few recorded for this carangid in the western Indian Ocean and represents the first subtropical aggregation of giant trevally. The aggregation is also the largest recorded for this species, with up to 2 413 individuals representing an estimated biomass of approximately 30 tonnes. The size and predictability of this annual aggregation make it vulnerable to overexploitation and point towards the need for an appropriate conservation management strategy. 相似文献
59.
Twenty years after the Exxon Valdez oil spill, scattered patches of subsurface oil residues (SSOR) can still be found in intertidal sediments at a small number of shoreline locations in Prince William Sound, Alaska. Some scientists hypothesize that sea otters continue to be exposed to SSOR by direct contact when otters dig pits in search of clams. This hypothesis is examined through site-specific examinations where SSOR and otter-dug pits co-occur. Surveys documented the exact sediment characteristics and locations on the shore at the only three subdivisions where both SSOR and otter pits were found after 2000. Shoreline characteristics and tidal heights where SSOR have persisted are not suitable habitat for sea otters to dig pits during foraging. There is clear separation between areas containing SSOR and otter foraging pits. The evidence allows us to reject the hypothesis that sea otters encounter and are being exposed by direct contact to SSOR. 相似文献
60.
The growth rate of speckled snapper Lutjanus rivulatus was investigated using data from a long-term tag-recapture study conducted in the St Lucia Marine Reserve within the iSimangaliso Wetland Park, a World Heritage Site in northern KwaZulu-Natal, South Africa. A total of 1 429 L. rivulatus were tagged and 453 (31.7%) individual fish were recaptured one or more times. Growth rates were modelled from the tag-recapture data using a maximum-likelihood approach. It is shown that L. rivulatus is a slow-growing species with L∞ = 918?mm FL, K = 0.06 and phi-prime (Ø, the growth index) = 2.69. The effects of deep-hooking and multiple captures were tested and this revealed that there was no significant impact on the growth of L. rivulatus. The growth index was lower than that recorded in many other similar congeneric species. Slow growth, coupled with high levels of residency and site fidelity, suggest that this species is vulnerable to exploitation and that a precautionary approach towards future management is appropriate. 相似文献