海岸测量中GPS水准精度控制的探讨

简要介绍了高程系统的概念,分析了GPS水准拟合的基本数学模型,探讨了已知水准点极少时GPS水准拟合的精度控制问题,得出的一些结论可供海道测量工作者在海岸高程控制测量中参考.     

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珠海市陆海统一似大地水准面精确求定

在海域广阔、河网密布的海滨城市珠海,基于区域陆海重力、地形数据,利用第二类Helmert凝集法精确求取了覆盖珠海市陆海全域的重力似大地水准面,解决了跨海岸线重力归算等关键问题;通过球冠谐调和分析法,将求取的重力似大地水准面与新测的高精度GNSS水准成果融合,获取了珠海市2'×2'陆海统一似大地水准面。以港珠澳大桥首级控制点为主的精度统计表明,该陆海统一似大地水准面模型外符合精度达到±0.008 m。     

A Gravimetric Geoid Computation and Comparison with GPS Results in Northern Andalusia (Spain)

Two new GPS surveys have been carried out to check the accuracy of an existing gravimetric geoid in a test area located in northern Andalusia (Spain). The fast collocation method and the remove-restore procedure have been used for the computation of the quasigeoid model. The Spanish height system is based on orthometric heights, so the gravimetrically determined quasigeoid has been transformed to a geoid model and then compared to geoid undulations provided by GPS and levelling at benchmarks belonging to the Spanish first-order levelling network. The discrepancies between the gravimetric solution and GPS/levelling undulations amount to ±2 cm for one survey and ±5 cm for another after fitting a plane to the geoid model.     

Deformation datum in source mechanism inversion

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Contemporary crustal deformations in the Izu peninsula,Honshu, Japan and acceleration of plate bending in the northernmost part of the Philippine Sea plate

Since the beginning of the anomalous vertical crustal movement in the Izu peninsul, Honshu, Japan, many repeated precise levellings have been carried out by the Geographical Survey Institute. Trilaterations covering the entire Izu peninsula have also been carried out by the Geographical Survey Institute. A new technique is developed to adjust the results of levellings, because they had been carried out for different epochs along each levelling route and because of rapid vertical crustal movements. In conventional least-squares adjustment of levelling network, only corrections to the approximate height are assumed to be unknown, while in the present analysis a special model in which rates of vertical deformation at any bench marks are also assumed to be unknown, is adopted. In addition, tidal stations along the coast of the Izu peninsula yield the rate of vertical crustal movement from analysis of tidal data independent of levelling data. We select several special bench marks in which rates of vertical movement are determined by tidal analysis, thereafter special adjustment is applied according to the type of network.The results show that the peninsula is inclined to the south-west. Uplift in the northeastern part of the peninsula is accompanied by remarkable subsidence in the southwest. The rate of contemporary inclination is many times higher than the rate during the period from 1929 to 1972.The deformation is concentrated in the area whereNakamura (1979, 1980) pointed out the bending of the Philippine Sea plate. The mode and rate of the detected crustal deformation suggest the accelerated bending of the peninsula. There are some local uplift that deviate from the general pattern of deformation. The most remarkable land uplift was observed near Ito, a city within the peninsula, and the focus of this uplift migrated with time. The accelerated plate bending will produce an extension at the earth's surface and contraction in the deeper part of the subcrustal layer, additionally it triggered the intrusion of magma from the deeper part to the shallower. Moreover, the accelerated plate bending also triggered seismic swarms and destructive, earthquakes in and around the peninsula.     

推算我国高精度和高分辨率似大地水准面的若干技术问题

讨论我国新一代高精度高分辨率似大地水准面的特点及其可能的精度和分辨率,列出了采用移去恢复法时的实用公式,介绍了计算斯托克司公式的严格方法和高程异常推估点的精度评定。     

光电测距三角高程测量在山区代替三,四等水准的可行性探讨

本文作者根据自己在工作实践中的尝试，对在山区用光电测距三角高程测量代替三、四等水准问题，谈了几点体会．     

祁连山北缘断裂带的现代构造运动

本文依据现今区域水准测量资料及跨断层位移测量资料阐明祁连山北缘断裂带现今活动特点是以近南北—北东向的挤压并兼有右旋走滑的水平活动方式为主,在玉门一张掖段并伴有近似反对称的升降运动,最大垂直形变梯度R为0.2毫米/公里·年左右,跨断层基线测量的缩短速率为0.2—0.5毫米/年。在河西走廊内部,受次级构造运动的影响也存在有局部的隆起、拗陷的升降运动及断裂活动