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张爱宁 《武汉大学学报(信息科学版)》1988,(2)
本文提出了一种适合在微机上实现的多边形地图叠置算法——矢量网格法。该法以矢量格式为基本数据格式,辅之以网格结构,具有数据结构简单、数据量小、求交效率较高的特点。但矢量数据的叠置处理极为复杂,为保证算法思想的可靠性,本文着重运用拓扑学中有关复合形的理论,证明了矢量网格法叠置算法若干前提的正确性。该法已在微机HITACHI MB-16007A上实现。初步试验表明该系统可行。 相似文献
585.
利用全球定位系统(GPS)所建立的空间基线向量网,对于改善已有地面网,分析网的系统误差和进行地球动力学的监测等具有广泛的意义。本文着重讨论了上述空间基线向量网和地面控制网的三维联合平差和二维联合平差的方法和模型。指出,为了避免地面网高程误差以及引入地面网尺度因子的模型误差对三维联合平差结果的影响,在二维大地坐标系统中进行上述两网联合平差的方法具有重要的现实意义。 相似文献
586.
Hartmut A. Spetzler Ganglin Chen Scott Whitehead Ivan C. Getting 《Pure and Applied Geophysics》1993,141(2-4):341-377
A new giga-Hertz ultrasonic interferometer has been developed, based on ultrasonic microscopy technology. The interferometer operates from 0.3 GHz to 1.5 GHz. The high frequency and associated small wavelengths together with the large bandwidth make it possible to measure travel times in samples with thicknesses of several microns and allow for unprecedented accuracy in bond corrections. An absolute accuracy of 1 part in 105 in travel time measurements is achievable in single crystals (thickness of 200 microns) or glasses of interest to the earth sciences. The high precision travel time data, combining with sample length measurements using a laser interferometer built in our laboratory, yield very high precision ultrasonic velocities.The interferometer is intended for use in conjunction with a newly developed 4 GPa gas piston cylinder apparatus (Getting andSpetzler, 1993) for equation of state measurements under simultaneous pressure and temperature. A separate correction for the bond will be made for each datum at every point in temperature pressure space. 相似文献
587.
Airborne very low frequency (VLF) data are routinely collected by national agencies and commercial companies together with
other passive geophysical measurements of the static magnetic field and radiometric data. The purpose of this paper is to
demonstrate that both standard three-component VLF and tensor VLF (TVLF) data contain a lot of useful quantitative and qualitative
information about the electrical conductivity distribution in the upper few hundred meters of the crystalline basement. We
first give a new derivation of the fundamental transfer functions (the tipper) used in the TVLF technique. We then show that
the tipper can be estimated from simultaneous measurements of the wave magnetic fields from at least two transmitters with
somewhat different frequencies, and present a simple model by which the maximum error introduced by the difference in frequencies
can be found. Single transmitter scalar VLF maps emphasise those conductive structures that have dominant strikes in the direction
of the transmitter. Multiple transmitter transfer functions are dependent only upon the underlying conductivity structure.
Two dimensional structures can be quantitatively modelled by modern inversion methods developed originally for deep electromagnetic
magnetotelluric (MT) soundings. In such cases three-component VLF measurements can be modelled easily upon appropriate rotation
of the co-ordinate system to “strike” co-ordinates. Single frequency transfer functions (tippers) have real and imaginary
parts that carry information on not only lateral contrasts in conductivity, as usually stated in text books, but, taken together,
they provide a robust tool for determining the background conductivity level away from distinct conductors, and they can also
be used to discriminate between deep and shallow conductors. Based upon simulations using multi-frequency data, it can be
concluded that such a new development would dramatically increase the resolving power of airborne VLF measurements. 相似文献
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主要介绍了“3S”技术及其在数据库数据更新方面发展的状况,并以1:250000数据库更新为例,简述了利用“3S”技术进行数据库数据更新的基本过程及步骤。 相似文献
590.