重力异常对静力水准系统测量精度的影响

讨论了在大距离范围中使用静力水准系统应注意的问题,根据地球潮汐理论,着重分析了由于附近巨大物体以及月球和太阳的作用引起的测量范围内的重力异常对系统测量精度的影响和相应的修正办法,并推导出了改正量公式。     

基于异常误差补偿的多期水准网动态平差

针对水准网中的异常误差,采用函数模型异常误差补偿方法抑制其影响,提高水准网平差精度。首先采用最小二乘方法获得各观测值残差,通过假设检验确定异常误差位置;将异常误差作为待估参数进行解算;最后扣除异常误差,利用"干净"观测数据进行平差获取水准网点的高程与垂直运动速度。采用山东省两期二等水准网观测数据进行试验,该方法进一步提高了水准网平差的可靠性。     

Unification of New Zealand’s local vertical datums: iterative gravimetric quasigeoid computations

New Zealand uses 13 separate local vertical datums (LVDs) based on geodetic levelling from 12 different tide-gauges. We describe their unification using a regional gravimetric quasigeoid model and GPS-levelling data on each LVD. A novel application of iterative quasigeoid computation is used, where the LVD offsets computed from earlier models are used to apply additional gravity reductions from each LVD to that model. The solution converges after only three iterations yielding LVD offsets ranging from 0.24 to 0.58 m with an average standard deviation of ±0.08 m. The so-computed LVD offsets agree, within expected data errors, with geodetically levelled height differences at common benchmarks between adjacent LVDs. This shows that iterated quasigeoid models have a role in vertical datum unification.     

数字水准仪应用于区域精密水准测量的有关问题研究

基于试验和实践,讨论了数字水准仪的特性和误差来源及其对观测结果的影响。在此基础上阐述了该仪器应用于区域精密水准测量中应予关注的各种问题和提高精度的措施。指出：应制定有关该仪器的测量规范。     

测距三角高程中的大气折射问题

根据国内不同地区的实测资料，综述了折光系数的测定方法及其变化特征等问题，提出了一些减弱折光影响的措施     

水准测量中的天文改正及精度分析

本文给出了水准测量中天文改正的计算公式,讨论了所给公式的精度,认为可满足精密水准测量的精度要求。计算所需的参数简单,便于实际作业。     

Vertical Displacements in the Nový Kostel Seismoactive Area

Since 1994 annual campaigns of precise levelling have been performed on the network established in the surroundings of Nový Kostel. The network covers the most dynamic part of the West Bohemia seismoactive region with a total of 70 points in 1999. The measurements are connected to a reference point of the national levelling system and to our GPS-gravity network. It was proved by the error and confidence level of the data that small displacements of three and more millimetres can be recognised. The data analysis showed that all points could be divided into several groups according to temporal changes of height. Mutual comparison of these changes enabled to detect both general and very local short-term movements. It appeared that, in general, the involved part of the mountain block is subsiding relative to the Cheb basin. This is in contradiction to the recent uplift of the Kruné hory Mts. The correlation between vertical displacements and earthquake swarms was examined with the conclusion that during a swarm period the movements have special homogeneous pattern, contrary to inter-periods. The division line of different displacements (a fault zone) for the swarms 1994 and 1997 was determined.     

Models for Fitting Gravimetric Geoids and GPS Results

The aim of this investigation is to study how to use a gravimetric(quasi) geoid for levelling by GPS data in an optimal way.The advent of precise geodetic GPS has made the use of a technique possible,which might be called GPS- gravimetric geoid determination.In this approach,GPS heights above the reference ellipsoid are determined for points whose levelled (orthometric) height H is above sea level people have already surveyed;for these points,we thus have the values of the geoid undulation N.These values are then used to constrain the geoid undulations N‘ obtained from the gravimetric solution.