全站仪自由设站应用于航道控制测量的图形研究

利用全站仪自由设站测边交会确定待定点的坐标,在航道控制测量工作中得到较好的应用。为研究待定点的精度与交会图形之间的关系,在推出全站仪自由设站测边交会精度估算公式的基础上,对其有利图形进行了分析,并通过实例证明:当采用对称交会(β1=β2),且交会角γ>90°时,交会图形最为有利。     

海洋重磁测网判定测线相交的实用方法

在海洋重磁调查领域,判断测网中2条测线相交与否是重磁数据处理中需要解决的重要问题之一,目标是能够快速准确地确定交叉点的位置,从而计算出交点差。针对以往计算方法的不足,利用计算几何学中同一平面上线段相交的几何特征和计算方法,通过排斥判断和跨越判断2个步骤,对线段的相交与否进行判别,编写的程序逻辑简洁、实用,避免了数学错误。在实际应用中,提高了判断线段相交的效率和准确性,取得了良好的效果。     

如何消除雾霾天气对全站仪野外检定的影响

在全站仪野外检定过程中通常采用光照准模式,该模式对较远距离点测量时需要较好的气象条件的配合.近年来,我国秋冬季节普发的雾霾天气使得仪器野外测量时无法精确照准目标,使检定工作不能顺利完成.本文主要探讨了应用智能全站仪的ATR照准模式进行全站仪野外检定的可行性,通过选用不同型号的全站仪用光照准模式及ATR照准模式进行野外检定,并对实验数据进行统计分析,得出了采用ATR照准模式进行野外检定可消除雾霾天气的不利影响,得到准确可靠地检定数据的实验结论.     

工业测量全站仪坐标测量精度检定方法

全站仪坐标测量在航空航天、大型设备制造业、特种异形工程和计量检测等领域有广泛应用,其坐标测量误差是最受关注的精度指标。与激光跟踪仪、关节臂等坐标测量技术不同,全站仪的标称精度指标并未直接给出点位坐标误差,而是分别给定测角和测距误差。由于国内外目前还缺乏将测角和测距精度对应到坐标精度的相应规范,这就导致不能直观反映全站仪的实际坐标测量精度,给具体测量工作的坐标精度估算带来一定难度。基于以上现状,提出了基于点对点长度测量和三维坐标测量误差的检定模型;并利用3种不同类型的工业测量全站仪进行了实验测试,验证了该检定模型的可行性。     

地缘战略交汇区地缘环境演变评估模型构建及其应用——以乌克兰为例

地缘环境研究是当前国内政治地理研究的重点和热点,在概念、内涵、分析框架、空间分异、系统模拟等领域已取得较大进展,但对于地缘战略交汇区这一特殊地缘政治区域的地缘环境研究鲜有涉及.论文基于地缘战略的空间和权力属性,融合政治地理学的地缘环境、地缘位势,国际关系学的现实主义、自由主义和建构主义等理论,兼顾主体间性的哲学思想,构...     

Determination of frame-dragging using Earth gravity models from CHAMP and GRACE

Using the new generation Earth’s gravity field models EIGEN-2S, GGM01S and EIGEN-GRACE02S generated by the space missions CHAMP and GRACE, we have obtained an accurate measurement of the Lense–Thirring effect with the LAGEOS and LAGEOS II satellites analyzing about 10 years of data with the EIGEN-2S and GGM01S models and about 11 years of data with EIGEN-GRACE02S. This new analysis is in agreement with our previous measurements of the Lense–Thirring effect using the LAGEOS satellites and obtained with the JGM-3 and EGM96 Earth’s models. However, the new determinations are more accurate and, especially, more robust than our previous measurements. In the present analysis we are only using the nodal rates of the two satellites, making no use of the perigee rate, as in our previous analyses. The perigee is affected by a number of non-gravitational perturbations difficult to be modelled and whose impact in the total error budget is not easy to assess. Using the EIGEN-2S model, we obtain a total error budget between 18% and 36% of the Lense–Thirring effect due to all the error sources. Specifically, by using EIGEN-2S, we obtain: μ = 0.85, with a total error between ±0.18 and ±0.36, with GGM01S we get μ = 1.06 with a total error between ±0.19 and ±0.24 and with EIGEN-GRACE02S we obtain μ = 0.99, with a total error between ±0.05 and ±0.1, i.e., between 5% and 10% of the general relativistic predicted value of the Lense–Thirring effect. In addition to the analyses using EIGEN-2S, GGM01S and EIGEN-GRACE02S without the use of the perigee, we have also performed an analysis using the older model EGM96 with our previous method of combining the nodes of the LAGEOS satellites with the perigee of LAGEOS II. However, this analysis was performed over a period of about 10 years, i.e. about 2.5 times longer than any our previous analysis. The result using EGM96 over this longer period of observation agrees with our previous results over much shorter periods and with the EIGEN-2S, GGM01S and EIGEN-GRACE02S measurements of μ. In addition to the accurate determination of frame-dragging and in agreement with our previous analyses of the orbits of the LAGEOS satellites, we have observed, since 1998, an anomalous change in the Earth quadrupole coefficient, J₂ which agrees with recent findings of other authors. This anomalous variation of J₂ is accurately observed both on the node of LAGEOS and LAGEOS II and it is independent of the model used, i.e., it is observed by using the model EGM96 or by using EIGEN-2S, GGM01S or EIGEN-GRACE02S. However, this anomalous variation of the Earth quadrupole coefficient does not affect at all our determination of the Lense–Thirring effect thanks to the total elimination of the J₂-induced errors with our especially devised estimation technique.     

北斗卫星导航系统SISURE初步评估

北斗导航系统自2018年12月27日提供全球服务以来,其服务性能受到了极大关注.以上海天文台iGMAS (International GNSS MonitoringAssessment System)分析中心发布的精密轨道、钟差产品作为基准,评估了2019年年积日3–12 d的北斗二号、北斗三号以及GPS广播星历的轨道、钟差和空间信号用户测距误差(Signal in Space User Ranging Error, SISURE,简称为URE),并且对北斗卫星导航系统结果进行了详细的分析.结果表明:在评估时间段内,北斗三号广播星历轨道精度、URE均明显优于北斗二号,且部分结果优于GPS.北斗三号广播星历轨道径向精度最高,优于0.2 m.北斗三号全部卫星URE均值优于0.4 m, URE RMS (root mean square)优于0.5 m.北斗二号每颗卫星URE均值、95%URE (置信度为95%的URE)、URE RMS小于2 m,北斗三号每颗卫星URE均值、95%URE、URE RMS小于1 m,均达到了系统公开承诺的服务性能标准.     

Altimetry and transponder ground simulation experiment

We have designed and built a compact demonstrator unit for the investigation of altimetry and transponder applications. A small light-weight breadboard carries a compact frequency doubled Nd:YAG pulse laser, an afocal beam expansion optics, a small receiver telescope with spectral and spatial filter arrangements and a sensitive photo-detector. The output laser energy can be as high as 45 mJ with a pulse-width of 3 ns and the telescope aperture is 10 cm. Simulations [Degnan, J.J., 2006. Simulating interplanetary transponder and laser communications experiments via dual station ranging to SLR satellites. In: Proceedings of the 15th International Workshop on Laser Ranging, Canberra, Australia, pp. 457-462] suggested that the link margin for low Earth orbiting satellites (LEO) is comfortable. Successful satellite laser ranging from this dual-station experiment in several different configurations was achieved up to the MEO orbit in a 10 day provisional installation.     

自适应光学技术应用于激光测月中大气波前倾斜量的探测与计算

针对云南天文台1.2米望远镜在激光测月中回波光子数太少的问题，将大气湍流效应考虑到激光测月中，研究了互相关和绝对差分两种跟踪算法的原理，并编写了算法程序，利用太阳数据验证了程序的正确性,给出了根据所采集的月面感兴趣区域的图像数据，用不同方法在不同条件下处理所得的大气波前整体倾斜信号，比较了算法的优劣。