Exploring gravity field determination from orbit perturbations of the European Gravity Mission GOCE   总被引：5，自引：0，他引：5  

P. N. A. M. Visser  J. van den IJssel  R. Koop  R. Klees 《Journal of Geodesy》2001,75(2-3):89-98

 A comparison was made between two methods for gravity field recovery from orbit perturbations that can be derived from global positioning system satellite-to-satellite tracking observations of the future European gravity field mission GOCE (Gravity Field and Steady-State Ocean Circulation Explorer). The first method is based on the analytical linear orbit perturbation theory that leads under certain conditions to a block-diagonal normal matrix for the gravity unknowns, significantly reducing the required computation time. The second method makes use of numerical integration to derive the observation equations, leading to a full set of normal equations requiring powerful computer facilities. Simulations were carried out for gravity field recovery experiments up to spherical harmonic degree and order 80 from 10 days of observation. It was found that the first method leads to large approximation errors as soon as the maximum degree surpasses the first resonance orders and great care has to be taken with modeling resonance orbit perturbations, thereby loosing the block-diagonal structure. The second method proved to be successful, provided a proper division of the data period into orbital arcs that are not too long. Received: 28 April 2000 / Accepted: 6 November 2000  相似文献   

Biomagnification and environmental quality criteria: a physiological approach     

Everts  J. W.; Eys  Y.; Ruys  M.; Pijnenburg  J.; Visser  H.; Luttik  R. 《ICES Journal of Marine Science》1993,50(4):333-335

  相似文献   

Hydraulic redistribution by deeply rooted grasses and its ecohydrologic implications in the southern Great Plains of North America     

Erik Oerter  Eric Slessarev  Ate Visser  Kyungjin Min  Megan Kan  Karis J. McFarlane  Malay C. Saha  Asmeret Asefaw Berhe  Jennifer Pett-Ridge  Erin Nuccio 《水文研究》2021,35(9):e14366

Perennial bioenergy crops with deep (>1 m) rooting systems, such as switchgrass (Panicum virgatum L.), are hypothesized to increase carbon storage in deep soil. Deeply rooted plants may also affect soil hydrology by accessing deep soil water for transpiration, which can affect soil water content and infiltration in deep soil layers, thereby affecting groundwater recharge. Using stable H and O isotope (δ²H and δ¹⁸O) and ³H values, we studied the soil water conditions at 20–30 cm intervals to depths of 2.4–3.6 m in paired fields of switchgrass and shallow rooted crops at three sites in the southern Great Plains of North America. We found that soil under switchgrass had consistently higher soil water content than nearby soil under shallow-rooted annual crops by a margin of 15%–100%. Soil water content and isotopic depth profiles indicated that hydraulic redistribution of deep soil water by switchgrass roots explained these observed soil water differences. To our knowledge, these are the first observations of hydraulic redistribution in deeply rooted grasses, and complement earlier observations of dynamic soil water fluxes under shallow-rooted grasses. Hydraulic redistribution by switchgrass may be a strategy for drought avoidance, wherein the plant may actively prevent water limitation. This raises the possibility that deeply rooted grasses may be used to passively subsidize soil water to more shallow-rooted species in inter-cropping arrangements.  相似文献   

The Crustal Structure From Teleseismic P-Wave Coda-I. Method     

Hanneke Paulssen  Jeanette Visser  Guust Nolet 《Geophysical Journal International》1993,112(1):15-25

  相似文献   

THE EUROPEAN ORGANISATION FOR EXPERIMENTAL PHOTOGRAMMETRIC RESEARCH (OEEPE)     

J. Visser  † 《The Photogrammetric Record》1982,10(60):655-668

Since the occasion of the Thompson Symposium in 1979, two new members have joined OEEPE. These are France and the United Kingdom. The possibility of membership had been considered by the UK over the last decade on more than one occasion but, for one good reason or another, no application had been made. In 1980, however, W. P. Smith (Director General, Ordnance Survey) circulated organisations and individuals who might be interested and received an almost unanimous expression of support for an application for membership. This was also in line with the Ordnance Survey's intent to increase its links with other organisations, both nationally and internationally. The Foreign Office agreed that the UK should apply for membership and this was done. The UK became a full member of OEEPE in time for the Oslo meeting of the Steering Committee in 1981.
There follows a background paper on the work of OEEPE and accounts of current OEEPE Commission activities.  相似文献   

The developmental impacts of backpacker tourism in South Africa     

Gustav Visser 《GeoJournal》2004,60(3):283-299

South Africa has recorded considerable growth in tourism activity over the past decade. In the light of the vast range of economic sectors that gain from tourism development, the national government has instituted a range of incentives and initiatives to stimulate tourism development, with the expansion of tourism infrastructure aimed at high-end tourists forming a key component of this strategy. Little investment has, however, been made in tourism infrastructure targeting those markets that prefer to avoid high-end tourism facilities. In this respect backpacker tourists and their preferred accommodation type, backpacker hostels, are a case in point. Despite backpacker tourism being largely ignored in national tourism development initiatives, backpacker tourism is increasingly popular in South Africa. This paper focuses on the recent proliferation of backpacker tourism in this country and seeks to convey the results of the first nation-wide exploration in this regard. The paper has two main objectives. Firstly, it seeks to present broad-ranging empirical data concerning this tourist cohort and their preferred accommodation type- backpacker hostels — in the South African context. Secondly, it aims to demonstrate why backpacker tourists and hostels hold much potential for local development initiatives in South Africa. In the light of the findings of this study, the paper concludes that the expansion of backpacker tourism to this country might form an appropriate means by which to achieve a range of local development objectives.  相似文献   

Precise GRACE baseline determination using GPS   总被引：13，自引：1，他引：13  

Remco Kroes  Oliver Montenbruck  William Bertiger  Pieter Visser 《GPS Solutions》2005,9(1):21-31

Precision relative navigation is an essential aspect of spacecraft formation flying missions, both from an operational and a scientific point of view. When using GPS as a relative distance sensor, dual-frequency receivers are required for high accuracy at large inter-satellite separations. This allows for a correction of the relative ionospheric path delay and enables double difference integer ambiguity resolution. Although kinematic relative positioning techniques demonstrate promising results for hardware-in-the-loop simulations, they were found to lack an adequate robustness in real-world applications. To overcome this limitation, an extended Kalman Filter modeling the relative spacecraft dynamics has been developed. The filter processes single difference GPS pseudorange and carrier phase observations to estimate the relative position and velocity along with empirical accelerations and carrier phase ambiguities. In parallel, double difference carrier phase ambiguities are resolved on both frequencies using the least square ambiguity decorrelation adjustment (LAMBDA) method in order to fully exploit the inherent measurement accuracy. The combination of reduced dynamic filtering with the LAMBDA method results in smooth relative position estimates as well as fast and reliable ambiguity resolution. The proposed method has been validated with data from the gravity recovery and climate experiment (GRACE) mission. For an 11-day data arc, the resulting solution matches the GRACE K-Band Ranging System measurements with an accuracy of 1 mm, whereby 83% of the double difference ambiguities are resolved.  相似文献   

The importance and quality of governance in the Chilean wine industry     

Evert-Jan Visser  Peter de Langen 《GeoJournal》2006,65(3):177-197

The central theme of this paper is the issue of the governance of cooperation within the Chilean wine industry. The effects of the internationalization of this industry for the importance and the quality of governance of intra-cluster cooperation involving firms and other actors are analysed. Two questions stand central. First, what has been the relative importance of external and internal factors in improving the export performance of the Chilean wine industry over the past 20 years? Second, to what extent have collective actions and investments played a part in this growth, and what has been the quality of the various governance regimes dealing with the associated collective action problems? Empirical evidence suggests that world-market developments and upgrading efforts by individual wineries largely explain the good export performance of the Chilean wine industry until the year 2000. The evidence also shows that the industry’s success in world markets is stimulating cooperation between firms and other actors in areas where the industry needs to improve: marketing and promotion, internationalization, innovation and training. The enhanced cooperation has not only stimulated cluster development, but has also turned the quality of cluster governance into a central variable for future export growth. Nevertheless, several collective action problems await resolution before essential intra-cluster cooperation can develop. Overall, the evidence suggests that, in the case of the Chilean wine industry, industrial and cluster development do not automatically follow enhanced integration in world markets, but depend on the strategic skills of actors within the industry, in particular their ability to identify, prioritize, and realize collective investments while effectively managing the associated collective action problems. Internationalization stimulates firms to consider such investments, however, and provides them with an incentive to upgrade strategic skills at the local level as new opportunities arise and the pressure is there to exploit them in world markets.  相似文献   

Time series analysis of monthly mean data of temperature,salinity, nutrients,suspended matter,phyto- and zooplankton at eight locations on the northwest european shelf     

M. Visser  S. Batten  G. Becker  P. Bot  F. Colijn  P. Damm  D. Danielssen  D. Van den Eynde  L. FØyn  A. Frohse  G. Groeneveld  R. Laane  W. van Raaphorst  G. Radach  H. Schultz  J. Sündermann 《Ocean Dynamics》1996,48(3-4):299-323

  相似文献   

The European Gravity Field and Steady-State Ocean Circulation Explorer Satellite Mission Its Impact on Geophysics   总被引：1，自引：0，他引：1  

J. A. Johannessen  G. Balmino  C. Le Provost  R. Rummel  R. Sabadini  H. Sünkel  C.C. Tscherning  P. Visser  P. Woodworth  C. Hughes  P. Legrand  N. Sneeuw  F. Perosanz  M. Aguirre-Martinez  H. Rebhan  M. Drinkwater 《Surveys in Geophysics》2003,24(4):339-386

Current knowledge of the Earth's gravity field and its geoid, as derived from various observing techniques and sources, is incomplete. Within a reasonable time, substantial improvement will come by exploiting new approaches based on spaceborne gravity observation. Among these, the European Space Agency (ESA) Gravity field and steady-state Ocean Circulation Explorer (GOCE) satellite mission concept has been conceived and designed taking into account multi-disciplinary research objectives in solid Earth physics, oceanography and geodesy. Based on the unique capability of a gravity gradiometer combined with satellite-to-satellite high-low tracking techniques, an accurate and detailed global model of the Earth's gravity field and its corresponding geoid will be recovered. The importance of this is demonstrated by a series of realistic simulation experiments. In particular, the quantitative impact of the new and accurate gravity field and geoid is examined in studies of tectonic composition and motion, Glaciological Isostatic Adjustment, ocean mesoscale variability, water mass transport, and unification of height systems. Improved knowledge in each of these fields will also ensure the accumulation of new understanding of past and present sea-level changes.  相似文献