京津地区GPS试验观测初步结果

本文介绍了1988年5月下旬在京津地区所作的我国首次GPS试验观测的情况,数据处理结果及同地面测量资料的比较。试验观测中使用了六台Trimble 4000 SX单频GPS接收机。观测结果表明,在60公里范围内利用目前卫星所提供的轨道信息,使用单频载波相位钡量GPS接收机,可以达到10mm+2×10~(-6)这样的测距精度,而高差的测定精度则要低一些。但60公里以上距离的观测结果不佳,有待进一步试验、研究。     

单、双频GP5接收机在工作中的精度对比分析

随着GPS在测量中应用的普及,对GPS应用的研究有了更广泛的扩展。而GPS接收机的不断更新与换代,更使得测量单位在产品的需求方面显得眼花缭乱,人们在普遍意义上单纯的认为,双频GPS接收机在解算精度上要优高于单频GPS接收机,其实不然。利用实际观测数据研究证明,对于GPS单、双频接收机,当测距大于10km时,夜间观测数据解算结果的精度要高于白天观测数据解算结果精度;当测距在几千米至十几千米时,GPS单频接收机解算结果的精度要高于GPS双频接收机的解算结果的精度,下面仅就单、双频接收机在不同作业环境下精度进行简要分析。     

GPS RTK在道路控制测量中的应用

目前的GPS控制测量基本上采用相对定位的测量方法。这就需要多台GPS接收机在相同的时间段内同时连续跟踪相同的卫星组,实施同步观测。同步观测时各GPS点组成的图形称为同步图形。在控制测量中,用GPS建立控制网,最精密的方法当属静态测量。对大型建筑物,如特大桥、隧道、互通式立交等进行控制,宜用静态测量。而一般公路工程的控制测量,则可采用RTK动态测量。这种方法在测量过程中能实时获得定位精度。当达到要求的点位精度,即可停止观测,提高了作业效率。     

GPS卫星定位系统误差来源分析

GPS卫星定位系统是以一定的卫星数量为基础，比较均匀的覆盖全球的导航定位（地面上GPS接收机和空中卫星的有效结合）无线电系统。对GPS控制网的A、B、C级精度要求来看，要想提高控制网的精度，GPS接收机是否有利于正确：解算模糊值，是控制网坐标的精确性和可靠性的关键。     

寿光市城区四等GPS控制网的建立

GPS测量定位技术以其定位精度高、作业条件低、操作简捷、效率高等优点被广泛应用于控制测量中。但GPS控制网的精度受观测精度、基线精度和起算点精度的影响。因此，如何保障和提高GPS测量控制网的精度，是一个值得讨论的话题。通过对寿光市城区四等GPS控制网的布设，探讨GPS测量技术在控制测量中的应用方法、精度及注意的问题。     

两种电离层延迟改正模型对星载单频GPS实时定轨精度的影响

采用单频星载GPS实测伪距和载波相位观测值,结合不同的电离层延迟改正模型进行模拟实时定轨实验,分析单频实时定轨的精度。不同轨道高度的低轨卫星实验结果表明,在卫星轨道较高(500 km以上)时,使用单频伪距观测值与改进的Klobuchar模型,实时定轨位置精度可达0.86 m(三维RMS),速度精度可达0.9 mm/s,接近甚至优于双频伪距实时定轨的轨道精度;使用单频码相无电离层组合观测值时,实时定轨位置精度可达0.54 m,速度精度可达0.55 mm/s。采用合适的电离层延迟改正模型,廉价的单频星载接收机可应用于微小卫星的实时定轨。     

流动GPS观测资料能否用于地壳垂直形变监测？——以中国大陆为例

长期GPS连续观测可获取高精度的垂直形变速度场,但多期GPS流动观测资料能否用于地壳垂直形变监测尚不明确。本文首先对中国大陆260个陆态网络基准站和2 000个GPS流动站1999~2019年的观测资料进行高精度统一处理,获得各站点的时间序列和速度场,对筛选出的226个基准站和226个流动观测站的垂直形变速度场进行比较分析。结果表明,95%的连续GPS观测站的垂直形变速率误差小于0.5 mm/a,约50%的流动GPS观测站的垂直形变速率误差大于1 mm/a,约40%的流动站与连续站的垂直形变速率残差值大于2 mm/a,且约50%的流动GPS站点的垂直形变趋势与连续站不一致。西部地区的流动GPS观测站的垂直形变监测精度比东部高,这可能与东西部的观测环境和站点稳定性存在差异有关。对GPS连续站和流动站的垂直形变速度场的精度和残差进行分析认为,中国大陆流动GPS观测资料不适用于监测垂直形变小于2 mm/a的地区。     

RTK技术在控制测量中的应用

RTK测量技术是以载波相位观测量为根据的实时差分GPS测量技术,其基本思想是：在基准站上设置1台GPS接收机,对所有可见GPS卫星进行连续地观测,并将其观测数据通过无线电传输设备,实时地发送给用户观测站;在用户站上,GPS接收机在接收GPS卫星信号的同时,通过无线电接收设备,接收基准站传输的观测数据,然后根据相对定位原理,实时地解算整周模糊度未知数并计算显示用户站的三维坐标及其精度。     

基于低成本单频u-blox接收机的GPS/BDS定向性能分析

针对高精度GNSS定向应用场景，通过实验对比对低成本单频u-blox接收机的数据质量和解算精度。结果表明，u-blox接收机GPS、BDS观测值的信噪比略低于测量型接收机；伪距精度分别为0.91 m、0.56 m，相位精度分别为1.35 cm、1.20 cm。在静态观测环境下，u-blox的定向精度可以达到航向0.2°/m和俯仰0.4°/m；动态环境下解算结果稍差，但也可以达到航向0.3°/m和俯仰0.6°/m，略低于高成本测量型接收机单频数据的实时动态定向精度。     

乌鲁木齐南山GPS跟踪站观测资料精度分析

乌鲁木齐天文站于2001年按照国家重大科学工程“中国地壳运动观测网络”基准站的要求,在乌鲁木齐南山站建立了GPS跟踪站(GUAO：GPS station of the Urumqi Astronomical Observatory),现已加入IGS网,并向IGS发送GPS观测资料。利用GAMIT软件,采用有基准算法对新建GPS跟踪站的观测资料进行了归算和精度分析,首次获得了该站在ITRF2000中毫米级精度的地心坐标。     

Preliminary study on plasma membrane fluidity of Psychrophilic Yeast Rhodotorula sp.NJ298 in low temperature

The ability of cell to modulate the fluidity of plasma membrane was crucial to the survival of microorganism at low temperature. Plasma membrane proteins, fatty acids and carotenoids profiles of Antarctic psychrophilc yeast Rhodotorula sp. NJ298 were investigated at -3 ℃, 0 ℃ and 8 ℃. The results showed that plasma membrane protein content was greater at -3 ℃ than that at 8 ℃, and a unique membrane polypeptide composition with an apparent molecular mass of 94.7 kDa was newly synthesized with SDS-PAGE analysis; GC analysis showed that the main changes of fatty acids were the percentage of unsaturated fatty acids (C18∶ 1 and C18∶ 2) and shorter chain saturated fatty acid (C10∶ 0) increased along with the decrease of the culture temperature from 8 ℃ to -3 ℃; HPLC analysis indicated that astaxanthin was the major functional carotenoids of the plasma membrane, percentage of which increased from 54.6±1.5% at 8 ℃ to 81.9±2.1% at -3 ℃. However the fluidity of plasma membrane which was determined by measuring fluorescence anisotropy was similar at -3 ℃, 0 ℃ and 8 ℃. Hence these changes in plasma membrane's characteristics were involved in the cellular cold-adaptation by which NJ298 could maintain normal plasma membrane fluidity at near-freezing temperature.     

Information for authors

正1 Aims and Scope Advances in Polar Science(APS)is an international,peer-reviewed journal jointly sponsored by the Polar Research Institute of China and the Chinese Arctic and Antarctic Administration.APS is a comprehensive academic journal dedicated to presentation of multi-disciplinary achievements in Arctic and Antarctic expeditions and research.Its primary purpose     

JOURNAL OF OCEAN UNIVERSITY OF CHINA

<正>Copyright Submfnion of a roanusatpt inks:that the work described has not been published before(exoept In the form of an abstrW or as part of a published lecture,review,or thesis);that it is not under consideration for publication elsewhere that its publication has been approved by ail     

Information for Authors

<正>The Journal of Ocean University of China(Oceanic and Coastal Sea Research)is a comprehensive academic quarterly sponsored by the Ocean University of China,published one volume per year.This journal is devoted to the publication of the theoretical and applied research results on oceanography and marine fisheries.The fieldcovered include the physical,chemical,biological,geo-     

Hydraulics and Hydrology in Mountain Areas

<正>The 35th IAHR World Congress was held in Chengdu,China from September 8 to September 132013.The title of the conference was:"The Wise Finds Pleasure in Water:Meandering through Water Science and Engineering".During the congress,1239 papers were presented in 139sessions for oral presentations and 7 sessions for poster presentations.After the Congress,a Committee was appointed to select some of the best papers presented at the Congress for publication,after a     

Sea ice thickness measurement in spring season in Bothnian Bay using an electromagnetic induction instrument

As an important component of the cryosphere,sea ice is very sensitive to the climate change.The study of the sea ice physics needs accurate sea ice thickness.This paper presents an electromagnetic-induction(EM) technique which can be used to measure the sea ice thickness distribution efficiently,and the successful application in Bothnian Bay.Based on the electromagnetic field theory and the electrical properties of sea ice and seawater,EM technique can detect the distance between the instrument and the ice/water interface accurately,than the sea ice thickness is obtained.Contrastive analysis of the apparent conductivity data obtained by EM and the value of drill-hole at same positions allows a construction of a transformable formula of the apparent conductivity to sea ice thickness.The verification of the sea ice thickness calculated by this formula indicates that EM technique is able to get reliable sea ice thickness with average relative error of only 12%.The statistic of all ice thickness profiles shows that the level ice distribution in Bothnian Bay was 0.4-0.6 m.     

Thermohaline structure inhomogeneity associated with polynia at the northern margin of Emery Ice-shelf

Based on the hydrographic data in austral summer during the 22nd Antarctic Expedition of China(2005/2006),some features can be found about the northern margin of Emery ice shelf as follows.The heat content in the surface layer(0-50 m) at the eastern end and the western end of the ice-shelf margin is much higher than that at the middle.The upper mixing-layer depth and the seasonal thermocline depth at the middle of the ice-shelf northern margin are much shallower than those at the both ends.However there is much less difference between the middle and the ends in the bottom layer.The remote sensing photos show that the inhomogeneity in the surface-layer water is closely related to the spatial distribution of the floes and polynia in the area.     

Phylogenetic analysis of cultivable bacteria isolated from Arctic sea-ice

Phylogenetic analysis based on 16S rDNA of 8 strains of cultivable bacteria isolated from Arctic sea-ice was studied.The results showed that strain BJ1 belonged to genus Planococcus,which was a genus of low mole percent G C gram-positive bacteria;strain BJ6 belonged to genus Burkholderia of β-proteobacteria and the rest 6 strain all belonged to γ-proteobacteria,of which strain BJ8 was a species of Pseudoalteromonas,strain BJ2-BJ5 and BJ7 were members of genus Psychrobacter.Phylogenetic analysis also indicated that bacteria of genus Psychrobacter of the isolates formed a relatively independent phylogenetic cluster in comparison with other bacteria belonged to genus Psychrobacter.     

Information for authors

正1 Aims and Scope Advances in Polar Science(APS)is an international,peer-reviewed journal jointly sponsored by the Polar Research Institute of China and the Chinese Arctic and Antarctic Administration.APS is a comprchensive academic journal dedicated to presentation of multi-disciplinary achievements in Arctic and Antarctic expeditions and research.Its primary purpose is to publish achievements in fundamental research,applied