2020年3月23日新疆拜城5.0级和7月13日霍城5.0级地震总结

2020年3月23日和7月13日,新疆天山中部地区分别发生拜城5.0级和霍城5.0级地震,其中拜城5.0级地震发生在南天山地震带中段,霍城5.0级地震发生在北天山地震带西段.系统总结2次地震前出现的地震活动和地球物理观测异常,结果表明:①拜城5.0级地震:震前主要存在5级地震成组和尼勒克钻孔应变中短期异常;②霍城5.0...     

利用解析法有效快速估计将来GRACE Follow-On地球重力场的精度

本文首次利用解析法有效快速估计了将来GRACE（Gravity Recovery and Climate Experiment） Follow-On地球重力场的精度. 第一,基于功率谱原理分别建立了新的GRACE Follow-On卫星激光干涉星间测量系统星间速度、GPS接收机轨道位置和轨道速度以及加速度计非保守力误差影响累计大地水准面的单独和联合解析误差模型. 第二,利用提出的GRACE卫星关键载荷匹配精度指标和美国喷气推进实验室（JPL）公布的GRACE Level 1B实测精度指标的一致性,以及估计的GRACE累计大地水准面精度和德国波兹坦地学研究中心（GFZ）公布的EIGEN-GRACE02S地球重力场模型实测精度的符合性,验证了本文建立的解析误差模型是可靠的. 第三,论证了GRACE Follow-On卫星不同关键载荷匹配精度指标和轨道高度对地球重力场精度的影响. 在360阶处,利用轨道高度250 km、星间距离50 km、星间速度误差1×10^-9m/s、轨道位置误差3×10^-5m、轨道速度误差3×10^-8m/s和非保守力误差3×10^-13m/s²,基于联合解析误差模型估计累计大地水准面的精度为1.231×10^-1 m. 本文的研究不仅为当前GRACE和将来GRACE Follow-On地球重力场精度的有效快速确定提供了理论基础和计算保证,同时对国际将来GRAIL（Gravity Recovery and Interior Laboratory）月球卫星重力测量计划的成功实施具有重要的参考意义.     

月球重力场模型研究进展和我国将来月球卫星重力梯度计划实施

本文介绍了基于国际探月观测数据建立的月球重力场模型:8×4、15×8、13×13、5×5、7×7、16×16-1/2/3、Lun60d、GLGM-1/2、LP75D/G、LP100K/J、LP165P、LP150Q和SGM90d;通过对比SST-HL/LL-Doppler-VLBI和SST-HL/SGG-Doppler-VLBI跟踪观测模式的优缺点,建议我国将来首期月球卫星重力测量计划采用SST-HL/SGG-Doppler-VLBI较优;其次,通过对比静电悬浮、超导和量子卫星重力梯度仪的优缺点,建议我国将来首期月球卫星重力梯度计划采用静电悬浮重力梯度仪;并建议我国将来首颗月球重力梯度卫星的轨道高度(50～100 km)选择在已有月球探测卫星的测量盲区,轨道倾角(90°±3°)设计为有利于月球卫星观测数据全球覆盖的近极轨模式。     

Performance comparison of semicodeless GPS receivers for LEO satellites

This report provides a detailed performance analysis of three semicodeless dual-frequency GPS receivers for use in low Earth orbit (LEO). The test set comprises the IGOR receiver, which represents a follow-on of the flight-proven BlackJack receiver, as well as two geodetic receivers (NovAtel OEM4-G2 and Septentrio PolaRx2), which are entirely based on commercial-off-the-shelf technology (COTS). All three receivers are considered for upcoming flight projects or experiments and have undergone at least a preliminary environmental qualification program. Using extensive signal simulator tests, the cold start signal acquisition, tracking sensitivity, differential code biases, raw measurement accuracy, and navigation accuracy of each receiver have been assessed. All tests are based on a common scenario that is representative of an actual space mission and provides a realistic simulation of the signal dynamics and quality on a scientific LEO satellite. Compared to the other receivers, the IGOR instrument exhibits a superior tracking sensitivity and is thus best suited for occultation measurements with low tangent point altitudes. The OEM4-G2 and PolaRx2 receivers are likewise shown to properly track dual-frequency GPS signals and normal signal levels and to provide accurate code and carrier phase measurements. Given their limited resource requirements, these receivers appear well suited for precise orbit determination applications and ionospheric sounding onboard of microsatellites with tight mission budgets.     

TRACEABILITY: TRACKING AND PRIVACY IN THE FOOD SYSTEM*

ABSTRACT. Lapses in food safety have spurred development of governmental traceability systems to track every stage of food production as part of a standardized information base. These systems form part of national and international government efforts to reduce food‐security risks and control food‐related disease outbreaks. The European Union, the United States, Japan, and Canada have traceability requirements now in various stages of implementation, as does the Codex Alimentarius. Traceability regulations require that, from farm (plant or animal) to fork, foods have a clear, verifiable record that tracks through all stages of cultivation, production, supplying, transporting, processing, and distribution. Traceability implies complete information control over the geography of one of life's most essential acts, eating. The apparent object of traceability is food, which seems to imply that human tracking is not part of the process, but food does not move on its own. Those people responsible at each stage for food transfers and transactions may go into the traceability database, making their locations part of the record and supporting precise monitoring of labor performance, consumer buying patterns, and ownership and management strategies. Given these capabilities, the development of public‐sector traceability systems demands careful consideration. Owners, especially large exporters and importers, are likely to see their needs and fears shape the system. The food workforce may well bear tracking's brunt. Consumers, the presumed beneficiaries of the systems, will probably resist direct incorporation (and full benefit), favoring their privacy over their safety.     

星载GPS观测数据预处理模型研究

星载GPS不同于地基GPS。为了进行基于星载GPS的低轨卫星精密定轨和地球重力场模型解算,本文研究了星载GPS观测数据的钟差改正、整周模糊度解算、周跳探测、卫星跟踪点改正、GPS天线相位中心偏移和改正等的模型,给出了对应的处理公式和处理过程。     

变速成图系统技术关键及其在塔中西部的应用

变速构造成图是解决塔中地区低幅度构造问题和落实圈闭的方法之一,速度场的求取精度以及深度转换方法是变速构造成图的两个关键环节.采用层位反偏移技术使叠后时间偏移成果仅仅成为方便反射层位解释追踪的桥梁,避开了叠后时间偏移算法本身产生的偏移偏差和偏移速度不准造成的偏移误差对速度场建立与构造成图精度的影响;利用叠加速度反演进行逐层层速度求取,用三维空间射线追踪图形偏移技术把零偏移距时间域T₀图进行空间偏移归位到深度域,生成深度构造图.     

SATELLITE GRAVITY SURVEYING TECHNOLOGY AND RESEARCH OF EARTH''S GRAVITY FIELD

This is a summarized paper. Two topics are discussed: Firstly, the concept, development and application of four kinds of satellite gravity surveying technology are introduced; Secondly, some problems of theory and method, which must be considered in the study of the Earth's gravity field based on satellite gravity data, are expounded.     

Estimating time parameters of overland flow on impervious surfaces by the particle tracking method

Abstract

Travel time and time of concentration T_c are important time parameters in hydrological designs. Although T_c is the time for the runoff to travel to the outlet from the most remote part of the catchment, most researchers have used an indirect method such as hydrograph analysis to estimate T_c. A quasi two-dimensional diffusion wave model with particle tracking for overland flow was developed to determine the travel time, and validated for runoff discharges, velocities, and depths. Travel times for 85%, 95% and 100% of particles arrival at the outlet of impervious surfaces (i.e. T_t85, T_t95, and T_t100) were determined for 530 model runs. The correlations between these travel times and T_c estimated from hydrograph analysis showed a significant agreement between T_c and T_t85. All the travel times showed nonlinear relationships with the input variables (plot length, slope, roughness coefficient, and effective rainfall intensity) but showed linear relationships with each other.

Editor D. Koutsoyiannis; Associate editor S. Grimaldi     

Using eye tracking to evaluate the usability of animated maps

Cartographic animation has been developed and widely used in geo-visualisation and many other areas in recent years.The usability of animated maps is a key characteristic affecting map users’effectiveness and efficiency in accomplishing tasks.In this paper,an eye tracking approach was proposed as a visual analytics method to evaluate the usability of animated maps by capturing participants’eye movement data and quantitatively analysing the accuracy(effectiveness)and response time(efficiency)of users’task completion.In the study,a set of animated traffic maps represented by three important visual variables(colour hue,size and frequency)was used for the usability evaluation.The experimental results showed that the usability of these three visual variables for cartographic animation affects the usability of animated maps.Red,yellow,and aqua were found to convey map information more effectively than other colour hues.Size was found to be more usable than colour hues for both animated maps and static maps.Usability was not found to be proportional to the playback rate of animated maps.Furthermore,the usability of the frequency,colour hue,and size was found to be related to the display’s size.We hope that the analysis approach presented in this paper and the results of this study will be of help in the design of cartographic animation displays with better usability.