共查询到18条相似文献，搜索用时 843 毫秒
1.
2.
3.
4.
应用抗差估计理论分析2000国家重力基本网 总被引：3，自引：1，他引：3
应用抗差估计理论，结合2000国家重力基本网的实际数据。通过大量的试算对2000国家重力基本网的数据进行分析比较，提出了符合2000国家重力基本网平差计算的抗差估计方法。 相似文献
5.
为研究重力场的时变特性,考虑到我国全国重力网布设和观测的现状,引入一种分段线性动态平差模型,用于流动重力网的平差处理。与传统静态平差模型相比,该模型可以得到更可靠的重力场变化特征。为验证模型的有效性,对我国全国重力网数据和模拟数据分别进行了动态平差和静态平差处理。结果显示,对于全国重力网数据,两种平差方法得到的重力变化率的平均差值为13.4×10~(-8)m·s~(-2)/a,最大差值达50×10~(-8) m·s~(-2)/a,且动态平差精度明显优于传统静态平差。对于模拟数据,动态平差结果中80%以上的平差值与理论值差值在1×10~(-8) m·s~(-2)/a以内,只有两个差值超过2×10~(-8)m·s~(-2)/a,而静态平差结果中只有44.4%的平差值与理论值差值在1×10~(-8) m·s~(-2)/a以内,差值超过2×10~(-8) m·s~(-2)/a的占21%。因此,本文提出的分段线性动态平差模型与传统静态平差模型相比能更有效地反映真实重力场的变化信息。 相似文献
6.
本文简要介绍了北京和南宁两个国际绝对重力基本网（IAGBN）点的点位和环境条件，列出了这些点上的首批绝对重力测量结果及所使用的仪器。在北京点的测量结果表明，不同仪器的测量结果间差异很小。将IAGBN点的1990年观测值通过换算后求得了同一城市的我国1985重力基本网（85网）点的重力值，与1981年意大利绝对重力仪IMGC的测量结果和85网的平差值作了比较。 相似文献
7.
陆态网络绝对重力基准的建立及应用 总被引：4，自引：0，他引：4
利用陆态网络100个基准站的首期观测数据,建立了基本覆盖我国大陆范围的高精度绝对重力基准,各基准站点值精度均小于5.0μGal/a,为相对重力联测提供了高精度起算基准点,可获得真实的相对重力联测平差结果,避免重复重力观测获得的重力场动态变化图出现畸变。成都基准台重复重力观测获得的重力变化规律表明,汶川地震前长期重力变化率达5.01±0.7μGal/a,如此大的震前重力变化很可能是由于地下物质运移引起的。联合绝对重力和GRACE卫星长期测量数据,根据二者系统偏差确定了武汉地区的地壳沉降速率,为-3.27±0.65mm/a。 相似文献
8.
9.
测线网平差是航空重力测量数据处理的重要环节，其核心是系统误差的补偿。系统误差的处理是航空重力测量中的难题之一，它既有系统性，又有随机性。本文在分析航空重力测量主要误差源基础上，提出了测线系统误差影响检测的方法，并介绍了一种通过测线交叉点平差进行系统误差补偿的途径。最后用一个实际观测网数据验证了这些方法的有效性和可靠性。 相似文献
10.
李金文 《武汉大学学报(信息科学版)》1992,(1)
本文讨论了不同的潮汐公式,及其引起的重力测量计算成果不一致的问题,计算了当潮汐改正公式不统一时,对我国范围内绝对重力测量、相对重力测量、重力仪长基线格值因子标定、重力仪短基线周期误差标定及物探重力控制测量成果的影响,分析了我国85重力基本网所选取的绝对重力控制点之间的一致性、控制点与我国85网相对联测平差结果的一致性、以及85网与我国一等重力控制同之间的一致性问题。最后,为统一我国重力控制测量成果提出了一些建议。 相似文献
11.
Erik W. Grafarend 《Journal of Geodesy》1985,59(2):124-138
Summary From a two-dimensional network adjustment it is well understood that the one orientation unknown of a theodolite frame is
estimable, once the orientation datum parameter, e.g., one azimuth, is fixed. In three-dimensional networks the problem of
estimability of three orientation unknowns inherent in a theodolite frame is more complex. Here we prove that not only the
classical horizontal orientation unknown is estimable (up to the datum degrees of freedom), but also astronomical longitude
and astronomical latitude which can be considered as two additional orientation unknowns of the theodolite frame moving with
respect to an earth-fixed equatorial frame of reference. Thus the theodolite instrument can be considered—at least theoretically—a
gradiometer measuring the variation of the directional parameters of the gravity vector from one point to another. Or up to
the datum degrees of freedom astronomical longitude and astronomical latitude can be determined from only theodolite observations
between exclusively terrestrial points. M?nicke (1982), has shown that despite the refraction problem the method works sufficiently
well in practice. 相似文献
12.
本文主要阐述经典的最小二乘间接平差和秩亏自由网平差的基准,并据此讨论秩亏自由网平差的实际应用。 相似文献
13.
An evaluation of some systematic error sources affecting terrestrial gravity anomalies 总被引：1，自引：2，他引：1
B. Heck 《Journal of Geodesy》1990,64(1):88-108
Terrestrial free-air gravity anomalies form a most essential data source in the framework of gravity field determination.
Gravity anomalies depend on the datums of the gravity, vertical, and horizontal networks as well as on the definition of a
normal gravity field; thus gravity anomaly data are affected in a systematic way by inconsistencies of the local datums with
respect to a global datum, by the use of a simplified free-air reduction procedure and of different kinds of height system.
These systematic errors in free-air gravity anomaly data cause systematic effects in gravity field related quantities like
e.g. absolute and relative geoidal heights or height anomalies calculated from gravity anomaly data.
In detail it is shown that the effects of horizontal datum inconsistencies have been underestimated in the past. The corresponding
systematic errors in gravity anomalies are maximum in mid-latitudes and can be as large as the errors induced by gravity and
vertical datum and height system inconsistencies. As an example the situation in Australia is evaluated in more detail: The
deviations between the national Australian horizontal datum and a global datum produce a systematic error in the free-air
gravity anomalies of about −0.10 mgal which value is nearly constant over the continent 相似文献
14.
我国大地测量学的进展和展望 总被引：8，自引：1，他引：7
回顾了我国大地测量工作的进展。面向 2 1世纪前期的我国经济和国防建设及科技和社会发展 ,展望了我国新世纪的大地测量 ,提出应逐步进入精确、动态、实时的现代化体系 ,即完善国家三维空间大地网 ;建立 GPS综合服务体系 ;提供导航和定位服务 ;测定地壳运动、电离层参数、大气中可降水份等信息 ;精化中国地区重力场参数 ;建立新的国家重力基准网 ;完成分米级精度的中国似大地水准面的推算 ;积极开展海洋和空间大地测量 ,为资源、环境的管理以及防灾监测做出应有的贡献。 相似文献
15.
Rolf König 《Journal of Geodesy》1990,64(2):111-125
In the adjustment of inertial position surveys the additional parameters describing the systematic errors of individual traverses
can be considered as deterministic or stochastic. The paper deals with various aspects of the deterministic or stochastic
approach by way of a standard functional model. If purely deterministic parameters are set up, the solvability of the least
squares problem depends on redundant observations like coordinate discrepancies of forward and backward runs or coordinate
differences at cross-over points of traverse networks. Inequalities are presented to handle the configuration problem for
any net and for several ways of introducing parameter sets. Also condition equations being geometrically explainable are developed
solving the datum problem in free adjustment applications.
Based on the Ebersberger Forst campaigns with a large amount of Ferranti, Honeywell and Litton data, numerical investigations
into the stochastic properties of the additional parameters and the observations follow. It turns out that additional parameters
for Honeywell and Litton data can be considered as stochastic parameters while for Ferranti data significant azimuth and time
dependent effects can be found. The investigations of true errors show that in case of the deterministic adjustment approach
a diagonal covariance matrix can be introduced and in case of stochastic additional parameters a first order Gauss-Markov
process serves as a good approximation for the stochastic behaviour of the observations. 相似文献
16.
基于星间测距的自主定轨必然存在星座的整体旋转和漂移,即存在星座空间基准的衰减问题,因此,卫星星座的空间基准维持是自主定轨的主要目标,也是自主定轨的核心问题之一。重点讨论卫星自主定轨中的空间基准维持方法,系统分析星地观测、星间/星地组合观测和星间观测3种观测模式下的卫星轨道参数估计方法,及其对应的空间基准维持方式;提出卫星自主定轨强基准和弱基准概念。强基准是指在星地观测或星间/星地组合观测条件下,强化地面高精度基准站坐标的定轨方式,此时卫星星座基准与地面跟踪站基准一致;弱基准是指在仅有星间链路观测条件下,采用卫星轨道信息先验弱约束的定轨方式,即弱基准是以先验轨道所对应的卫星星座的几何重心建立的。强基准充分利用了星间、星地观测网中的各类信息,计算结果可靠且精度稳定,而弱基准虽然缺少地面观测信息,但先验卫星轨道同样是基于地面跟踪网精密定轨得到的,对卫星空间基准的维持同样可靠,且定轨计算更为简单。采用北斗试验星实测数据,分别开展无基准、弱基准和强基准支持下的自主定轨试验,试验结果表明,弱基准中仅对卫星轨道倾角和升交点赤经进行先验弱约束即可抵偿卫星星座的旋转和漂移,但定轨精度略低于强基准支持下的定轨精度。在无地面跟踪系统支持的特定环境下,建议采用弱基准方法,实现真正意义上的自主定轨。 相似文献
17.
C. David McLellan 《Journal of Geodesy》1974,48(4):335-347
Current coordinate values are based on the 1927 North American Datum. At the time of re-adjustment based on this datum Canadian
triangulation consisted of limited networks along and close to the U.S. boundary. Since then, loops of triangulation have
been built up and adjusted one by one as completed. Distortions resulting from this process have become evident with the introduction
of electronic distance measuring equipment.
In March 1972 a program was initiated to assess the existing horizontal control framework in Canada to determine how it should
be strengthened and extended to form a reasonably uniform control grid and to meet long range needs. Results indicate where
there are weaknesses and distortions in the existing networks. Using adjustment program GALS the network was processed and
evaluated in sections. The evaluation and classification is based on confidence region.
A complete re-adjustment of the framework is planned. A redefinition of datum based on satellite observations will likely
be one step. Strengthening and completion of the framework is essential. The assessment project aids in identifying weak areas
and prepares all data in computer compatible form for the first time. The data eventually will be entered on an automated
file from which information can be drawn for further adjustments and analysis.
A method of adjustment by sections is being investigated as a possible way of re-adjusting the framework. How satellite observations
will be used is not yet determined.
Paper presented at the International Symposium on Computational Methods in Geometrical Geodesy, Oxford, September 2–8, 1973. 相似文献
18.