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在精密水准测量时，由于温度的变化引起因瓦水准标尺的长度变化，致使水准测量成果中存在一定的系统误差。在多数情况下，一等水准测量是沿着坡度较小的路线进行，因此由于温度变化引起的因瓦水准标尺检定时的长度与作业时的长度不一致所产生的系统误差是不大的。但是，由于地震垂直形变测量的特 相似文献
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<正> 根据国家测绘局“七五”重点科研项目C87-02的总体设计要求,在对水准标尺温度改正问题进行了全面研究的基础上,提出了关于在精密水准测量中施加因瓦标尺温度改正的研究报告。根据国内外的研究和我们的研究结果,认为在我国具体条 相似文献
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在精密水准测量时,由于温度的变化引起因瓦水准标尺的长度发生变化,致使水准测量成果中存在一定的系统误差。在多数情况下,由于一等水准测量是沿着坡度较小的路线进行,因此由于温度变化所引起的,因瓦水准标尺检定时的长度与作业时的长度不一致所产生的系统误差是不大的。但是,在地震战线,由于垂直形变测量的特殊性——精度要求高,常沿着坡度很大的路线进行测量,以及多次重复测量。因此,在成果归算和计算形变量时,是否需要顾及温度对因瓦水准标尺长度的影响,有必要作进一步的探讨。 相似文献
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<正> 一、前言在精密水准测量中,观测高差必须加入尺长改正。因此,在使用过程中,必须以很高的精度测定它们的长度或监测它们的长度变化。对标尺进行精确检定的手段很多,比长器就是其中的一种。比长器是精密水准测量中测量因瓦标尺的平均米长、监测标尺长度变化和测定其温度系数的仪器。在标准米尺上标定其长度后,可以测定被测尺的长度,然后再由标准米尺的尺长方程式和气温,计算被测尺在标准温度下的长度。我们提出的比长器是1米间隔,称做1米比长器。标准米尺是线胀系数很小、经过计量部门检定的1米长标准线纹尺,要求达到二级标准。利用这种装置,精密水准测量作业小组,可以在一般的室内条件下对因瓦标尺进行检测。 相似文献
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在精密水准测量时,通常因瓦水准标尺是在水平位置进行检定的,但是在水准测量时,水准尺是处于直立状态。因而人们不禁要问:在两种不同的情况下,标尺的长度是否相等?为了回答这个问题,我们有必要先介绍有关因瓦水准标尺的结构大意。因瓦水准尺是由因瓦带(带上采用“样版喷涂法”或“直接刻制法”复制一排或两排分划线)和木质尺身所构成。木质尺身是由经过特殊处理的优质松木所制成,能抵御湿度的影 相似文献
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因瓦水准尺作为精密水准测量系统的组成部分,其质量的高低直接影响到水准测量成果的精度.分析了不同制造方法对因瓦水准尺分划线质量的影响;研究了不同品质的分划线获得检定结果的质量;介绍了因瓦水准尺检定的技术要求. 相似文献
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本文给出了激光准直系统垂直折光改正的数学模型。在温度梯度的精确值难以获得时,利用精密水准成果计算折光系数是行之有效的办法,文中还以BEPC工程为例,讨论了模型的具体应用。 相似文献
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G. K. Sherurah 《Journal of Geodesy》1970,44(1):71-85
This paper is a summary of an unpublished paper and it attempts to give a complete solution of the problem posed by the presence
of systematic errors in precise spirit levelling, using mathematical statistics. Distribution-free statistics, which do not
require the precise knowledge of the distribution of the underlying populations, are used and to this end, a value of the
expected systematic error in any given section is isolated from the total discrepancy of the independent mutual levelling
operations thus facilitating a plausible least square adjustment of the geodetic network. The problem of weighting is considered
in relation to the rank test-statistics. Complete mathematical derivations are not attempted in this summary. 相似文献
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《测量评论》2013,45(7):32-33
AbstractThe following note may be of interest to those responsible for or engaged in trigonometrical reconnaissance and observing, precise levelling, topographical mapping, and other branches of surveying where telescopes or field-glasses are used for long-distance work, especially when visibility is low. 相似文献
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Precise gravity measurements have repeatedly been carried out in the area around Lake Biwa in Japan since 1950 in order to
detect the secular change of gravity. The results obtained so far show that gravity change observed on the west line of the
first order levelling route around the lake during the period of 1971∼1975 was consistent with the results of levelling surveys.
This evidence shows that precise gravity measurement is one of the powerful methods for detecting vertical crustal movement. 相似文献
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《测量评论》2013,45(89):134-140
AbstractThe formulae given in this paper can be used for a station adjustment at a trigonometric station and also for the adjustment of errors in a level survey. As applied to levelling, the problem consists in finding the most probable values of the reduced levels of a number of points where the observed level differences between the points are not consistent with each other. It can be shown that the required values of the reduced levels are those which reduce the sum of the squares of the residual errors to a minimum, where the residual error is defined as the difference between the calculated and observed levels. 相似文献
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IGS各分析中心提供的北斗精密轨道和精密钟差产品可能因采用不同的天线相位中心模型而存在一定差异，其对精密产品之间的比较以及利用精密产品评估北斗空间信号精度会产生一定影响。首先利用实测观测数据深入分析了采用不同天线相位中心改正模型对精密轨道和钟差的影响规律，在此基础上提出了顾及不同天线相位中心改正模型的北斗空间信号精度评估方法，以欧洲定轨中心、德国地学中心、武汉大学提供的精密轨道和钟差作为参考，对北斗广播轨道、广播钟差以及空间信号精度进行了分析和比较。结果表明，在考虑了卫星天线相位中心改正模型的差异之后，采用不同分析中心提供的北斗精密轨道和精密钟差作为基准评估出的空间信号精度基本一致，地球同步轨道卫星优于1.68 m，倾斜地球同步轨道卫星优于0.78 m，中地球轨道卫星优于0.66 m，验证了所提出的评估方法的正确性。 相似文献
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三角高程法超长距离跨海高程传递实验研究 总被引：2，自引：0，他引：2
针对三角高程法跨海高程传递测量误差的来源问题,该文提出了基于三角高程法的超长距离跨海高程传递方法,设计了具体的测量方案,包括跨海场地选定与布设,观测标灯设计与制作,跨海观测时段数、测回数及组数设计,观测程序与观测方法、观测成果的限差验算与成果取舍等,并提出了跨海高程传递精度评定的两种方法。在平潭海峡公铁两用大桥工程现场选定两条跨海线进行了实验研究,实验结果表明,13.9km和18.0km跨距的跨海高差平差值与已知高差的较差均小于二等水准测量限差,每千米跨海高程测量中数的中误差分别为±0.68mm和±0.63mm。 相似文献
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The use of GPS for establishing height control in an area where levelling data are available can involve the so-called GPS/levelling technique. Modelling of the GPS/levelling geoid undulations has usually been carried out using polynomial surface fitting, least-squares collocation (LSC) and finite-element methods. Artificial neural networks (ANNs) have recently been used for many investigations, and proven to be effective in solving complex problems represented by noisy and missing data. In this study, a feed-forward ANN structure, learning the characteristics of the training data through the back-propagation algorithm, is employed to model the local GPS/levelling geoid surface. The GPS/levelling geoid undulations for Istanbul, Turkey, were estimated from GPS and precise levelling measurements obtained during a field study in the period 1998–99. The results are compared to those produced by two well-known conventional methods, namely polynomial fitting and LSC, in terms of root mean square error (RMSE) that ranged from 3.97 to 5.73 cm. The results show that ANNs can produce results that are comparable to polynomial fitting and LSC. The main advantage of the ANN-based surfaces seems to be the low deviations from the GPS/levelling data surface, which is particularly important for distorted levelling networks. 相似文献