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1.
IntroductionGeophysics as its nameindicates has to do withthe physics of the earth and its surrounding at-mosphere . Gilbert’s discovery that the earth be-haves as a great and rather irregular magnet andNewton’s theory of gravitation may be said toconstitute the beginning of geophysics . Miningand the search of metals date from the earliestti mes , but the scientific record began with thepublicationin 1956 of the famous treatise De remetallica by Georgius Agricola , whichfor manyyears was …  相似文献   

2.
Geographical Information Science is essentially computational geography and has its own research program, namely all aspects of formal models for spatial natural processes and the interaction of humans with the environment in space and time. This is not a question of technology and technology-related research; but technology influences what questions can be researched effectively. Collection of data in the field and the simulation of field experience through Virtual Reality are just two questions of how spatial reality and human experience are linked. The focus on human spatial cognition is similarly found in software engineering for interoperable Geographic Information Systems.  相似文献   

3.
Introduction WithGPSreceiversmountedonLEOsatel lites,GPSoccultationeventscanbeobserved.Theobservablesarevaluableforatmospheric monitoringandweatherforecasting.Whenpre paringtobuildupanLEOsatelliteoccultation observationsystem,theevaluation,designand imple…  相似文献   

4.
The temporal change of the rotation vector of a rotating body is, in the first order, identical in a space-fixed system and in a body-fixed system. Therefore, if the motion of the rotation axis of the earth relative to a space-fixed system is given as a function of time, it should be possible to compute its motion relative to an earth-fixed system, and vice versa. This paper presents such a transformation. Two models of motion of the rotation axis in the space-fixed system are considered: one consisting only of a regular (i.e., strictly conical) precession and one extended by circular nutation components, which are superimposed upon the regular precession. The Euler angles describing the orientation of the earth-fixed system with respect to the space-fixed system are derived by an analytical solution of the kinematical Eulerian differential equations. In the first case (precession only), this is directly possible, and in the second case (precession and nutation), a solution is achieved by a perturbation approach, where the result of the first case serves as an approximation and nutation is regarded as a small perturbation, which is treated in a linearized form. The transformation by means of these Euler angles shows that the rotation axis performs in the earth-fixed system retrograde conical revolutions with small amplitudes, namely one revolution with a period of one sidereal day corresponding to precession and one revolution with a period which is slightly smaller or larger than one sidereal day corresponding to each (prograde or retrograde) circular nutation component. The peculiar feature of the derivation presented here is the analytical solution of the Eulerian differential equations.  相似文献   

5.
IntroductionThe GRACE (gravity recovery and cli mate ex-peri ment) mission,twin satellites flying in for-mation ,which carries several key payloadsinclu-ding KBR (K-band ranging) system, waslaunchedin 2002 . The unique design of GRACEmissionis expected to lead to ani mprovement inseveral orders of magnitude in these gravitymeasurements and allow much i mproved resolu-tion of the Earth gravity field of finer scale overbothland and ocean to study a lot of geosciencesphenomena[1]. Though th…  相似文献   

6.
Satellite-to-Satellite Tracking in low-low model （SST-Ⅱ） is a new technique to resolve the series of problems met in the determination of the earth＇s gravity field. As the key technique of SST-Ⅱ, KBR can get SST-Ⅱ measurements directly. So the KBR performance analysis is the first step in SST-Ⅱ design. In this paper, assuming that the satellite pairs of SST-Ⅱ are in near circle polar orbits, the spectrum relationship between the earth gravity field and KBR is established using analytic method. And then some examples are analyzed, the suggestions and conclusions are drawn from these examples. The research results could be taken as a reference for future satellite gravity project of China.  相似文献   

7.
SUILi-chun 《测绘学报》2004,33(1):63-70
激光扫描数据提供了一种新的手段用于获取高精度的数字地形表面模型. 原始的航空激光扫描数据表达的是一些非规则分布的"点云", 这些非规则分布的点需要进行有效的事后处理. 这种事后处理有2个目的:一是将那些分布在地表面上的点(即地面点)与分布在非地表面上的点(譬如树木、房屋或汽车上的点, 即非地面点)进行有效的分离;二是从分离后的地面点中提取结构线, 用于建立高精度的数字地面模型. 作者发展了一系列的基于数字形态学理论和稳健参数估计理论的方法用于分离和探测地面点. 这里所介绍和开发的提取结构线的算法建立在数字图像处理和表面曲率理论的基础上. 这些算法同样可以扩展地用于其他领域. 所介绍的基于数字图像处理理论处理原始的航空激光扫瞄数据和提取结构线的方法取得了很好的结果. 这一结论可以在本文中通过一系列的插图得到有力的证明.  相似文献   

8.
The Chinese Loess Plateau has experienced drastic human-induced ecological degradation in the last century. The Chinese government has initiated a longterm project to restore the ecology and thus the environment. This effort requires information about the ecological potential, especially about the potential distribution of forests. This study first presented a complete procedure for spatially modeling the potential distribution of broadleaved deciduous forests (BDF) in the western part of the Chinese Loess Plateau. The procedure efficiently integrated the spatially distributed environmental variables using a machine learning approach (i.e., GARP) that extracted rules and patterns from the massive datasets. The GARP-produced composite map revealed that BDF can potentially be distributed continuously in almost all of the areas where annual precipitation is above 450 mm and BDF has discontinuous or sporadic distribution in areas where annual precipitation is below 450 mm. The discontinuously distributed BDF occurs in two different physiographic settings. The first setting is the higher-elevation mountains within the area between 450 and 400 mm isohyets, where effective soil moisture is considerably higher than low-elevation valleys due to reduced evaporation and increased precipitation. The second setting is the north-facing slopes of rocky terrain within the area north to the 450 mm isohyet, where evaporation is significantly reduced. We believe that the modeled result can effectively facilitate forestation planning for this area. In addition, the results may function as a base against which to estimate the historic changes in land cover and land use, to assess the ecological potential for carbon sequestration, and to evaluate the climatic significance of land-air interactions.  相似文献   

9.
G. Bourda 《Journal of Geodesy》2008,82(4-5):295-305
The temporal variations of the Earth’s gravity field, nowadays routinely determined from satellite laser ranging (SLR) and GRACE (Gravity Recovery And Climate Experiment), are related to changes in the Earth’s rotation rate through the Earth’s inertia tensor. We study this connection from actual data by comparing the traditional length-of-day (LOD) measurements provided by the International Earth Rotation and Reference Systems Service (IERS) to the variations of the degree-2 and order-0 Stokes coefficient of the gravity field determined from fitting the orbits of the LAGEOS-1 and −2 satellites since 1985. The two series show a good correlation (0.62) and similar annual and semi-annual signals, indicating that the gravity-field-derived LOD is valuable. Our analysis also provides evidence for additional signals common to both series, especially at a period near 120 days, which could be due to hydrological effects.  相似文献   

10.
On October 28 of 2006 the surveying and mapping discipline of Wuhan University celebratedher 50th birthday . More than 2 000 friends and alumni at home and abroad attended the cele-bration .The president of Wuhan University ,the academician of the Chinese…  相似文献   

11.
Through 50 years＇ untiring efforts and innovation, the surveying and mapping discipline of Wuhan University has undergone an extraordinary course. In October 2006, she will celebrate her 50th birthday. On this occasion, we would like to pay our great tribute and express our sincere gratitude to officials at different levels, alumni at home and abroad, people and friends of all walks of life, who have been supporting the construction and development of the discipline over the years.  相似文献   

12.
In this paper, the results of a cartometric analysis of a number of Portuguese and Spanish charts of the sixteenth and seventeenth centuries are presented and conclusions are drawn concerning the length of the degree of latitude adopted in the Iberian nautical cartography of the Renaissance. Under the light of what we know about the navigational and charting methods of the time, a new interpretation of the textual and cartographic sources is proposed. Rather than being the result of technical considerations or precise measurements, the adoption of the various standards during this long period appears to be no more than the echoes of the traditional models of the Earth and of the political disputes between Portugal and Spain.  相似文献   

13.
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14.
One of the most impor tant factors impacting the development of today‘s private higher education in China is that there are not enough policies to support in.Then,the history of private higher educationin Nanjing Nationalist Government(1927-1749)is focused on.  相似文献   

15.
This paper reports some researches on distribution of large volume image data using techniques of the Mixed Mode of Java Servlet and COM on Web. The architecture and key technologies are discussed in detail. The web distribution system of image is implemented and the system is tested by the application instances. At last, the advantages and disadvantages for this web image distribution mode are analyzed.  相似文献   

16.
The global landscape in the supply, co-creation and use of geospatial data is changing very rapidly with new satellites, sensors and mobile devices reconfiguring the traditional lines of demand and supply and the number of actors involved. In this paper we chart some of these technology-led developments and then focus on the opportunities they have created for the increased participation of the public in generating and contributing information for a wide range of uses, scientific and non. Not all this information is open or geospatial, but sufficiently large portions of it are to make it one of the most significant phenomena of the last decade. In fact, we argue that while satellite and sensors have exponentially increased the volumes of geospatial information available, the participation of the public is transformative because it expands the range of participants and stakeholders in society using and producing geospatial information, with opportunities for more direct participation in science, politics and social action.  相似文献   

17.
The policy of the Chinese government concerning the horizontal expansion of the cultivated land through the reclamation of desert soils result in a total increase of 665. 985 km^2 during the period 1987-1999 in North Shaanxi. This increase is less than the loss in arable land by urbanization. The accelerated rate of change in agricultural areas calls for more rapid surveys of urbanization and loss of arable land. Remote sensing has a number of advantages over ground-based methods for such surveys. The multi-scale concept of remote sensing data help us study the problem in four towns. Several maps were produced to analyze the situation of urban coverage in different times. The evaluation of the status, rate and risk of urbanization are based on an accepted average of urban increase as 2% of population growth per year.  相似文献   

18.
The topographic potential and the direct topographic effect on the geoid are presented as surface integrals, and the direct gravity effect is derived as a rigorous surface integral on the unit sphere. By Taylor-expanding the integrals at sea level with respect to topographic elevation (H) the power series of the effects is derived to arbitrary orders. This study is primarily limited to terms of order H 2. The limitations of the various effects in the frequently used planar approximations are demonstrated. In contrast, it is shown that the spherical approximation to power H 2 leads to a combined topographic effect on the geoid (direct plus indirect effect) proportional to H˜2 (where terms of degrees 0 and 1 are missing) of the order of several metres, while the combined topographic effect on the height anomaly vanishes, implying that current frequent efforts to determine the direct effect to this order are not needed. The last result is in total agreement with Bjerhammar's method in physical geodesy. It is shown that the most frequently applied remove–restore technique of topographic masses in the application of Stokes' formula suffers from significant errors both in the terrain correction C (representing the sum of the direct topographic effect on gravity anomaly and the effect of continuing the anomaly to sea level) and in the term t (mainly representing the indirect effect on the geoidal or quasi-geoidal height). Received: 18 August 1998 / Accepted: 4 October 1999  相似文献   

19.
The problem of fitting a pre-existing geoid on local GPS/LEV points is first taken into account, a possible way for its solution is proposed, based on techniques similar to the aerophotogrammetric absolute orientation.This approach is then used to compute themapping geoids of Sardinia and Calabria i.e. geoids with decimetric accuracy, needed for the heigthing of large scale maps. The pre-existing geoids EAGGI by Brennecke et al. (1983), and EGG2 by Denker et al (1993) are utilized, fitted on points of GPS/LEV traverses.The complete input-output data, the contour maps of both geoids, and a substantial checking on some Calabrian GPS/TRIG points of the entreprise IGM.95 are finally reported.  相似文献   

20.
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