TLS算法在参考球标定场中的应用

精密工程测量领域,对仪器有着极高的要求,需要定期对仪器的各项性能指标进行检定。仪器的检定和精度标定都需要有一定的基准,并用来评价仪器的性能。文中以球体为基准建立空间标定场,提出利用TLS(整体最小二乘平差)算法拟合球面的方法,并对比分析该方法的可行性;提出在满足精度要求下,参考球的选择方法;理论加实例分析,验证该方法的合理性。     

利用半经验模型的土壤水分反演方法

针对土壤水分反演经验模型使用范围受限、而理论模型相对复杂的问题,该文利用积分方程模型及经验相关长度定标模型,分析均方根高度、地表相关长度、土壤体积含水量对雷达后向散射系数组合的影响;结合RADARSAT-2全极化C波段雷达数据和野外实测数据,构建研究区均方根高度反演模型;将该模型与Dubois模型、介电模型进行结合以反演表层土壤含水量,并对反演值进行线性校正,最终实现裸土区表层土壤水分反演。实验结果表明,HH、VV极化下土壤水分实测值与反演值绝对误差在0.06内的点数分别达到总点数的78%和68%,证明该方法具有一定的可靠性和实用性,可为地表均方根高度、土壤水分反演提供方法和借鉴。     

四川丹棱机载SAR点目标辐射定标方法

作为机载SAR极化合成孔径雷达数据应用必不可少的步骤,SAR辐射定标将图像像素值转化为地物的后向散射系数。利用点目标进行辐射定标的方法具有简单、易于操作的特点且具有一定精度,被人们广泛应用于实际的生产中。三面角反射器稳定性较好且易于操作,并拥有较大的散射截面积,在较宽的角度变化范围内其在雷达系统中的散射截面积变化较小,所以被当成最常用的点目标定标器。本文在阐述点目标辐射定标的基础上,以四川省丹棱县为实验区域,进行基于点目标的辐射定标外定标,得出了该方法具有一定精度且简单实用的特性。     

Improving runoff prediction using agronomical information in a cropped,loess covered catchment

Predicting runoff hot spots and hot‐moments within a headwater crop‐catchment is of the utmost importance to reduce adverse effects on aquatic ecosystems by adapting land use management to control runoff. Reliable predictions of runoff patterns during a crop growing season remain challenging. This is mainly due to the large spatial and temporal variations of topsoil hydraulic properties controlled by complex interactions between weather, growing vegetation, and cropping operations. This interaction can significantly modify runoff patterns and few process‐based models can integrate this evolution of topsoil properties during a crop growing season at the catchment scale. Therefore, the purpose of this study was to better constrain the event‐based hydrological model Limburg Soil Erosion Model by incorporating temporal constraints for input topsoil properties during a crop growing season (LISEM). The results of the temporal constraint strategy (TCS) were compared with a classical event per event calibration strategy (EES) using multi‐scale runoff information (from plot to catchment). The EES and TCS approaches were applied in a loess catchment of 47 ha located 30 km northeast of Strasbourg (Alsace, France). A slight decrease of the Nash–Sutcliffe efficiency criterion on runoff discharge for TCS compared to EES was counterbalanced by a clear improvement of the spatial runoff patterns within the catchment. This study showed that limited agronomical and climatic information added during the calibration step improved the spatial runoff predictions of an event‐based model. Reliable prediction of runoff source, connectivity, and dynamics can then be derived and discussed with stakeholders to identify runoff hot spots and hot‐moments for subsequent land use and crop management modifications.     

Deriving the relationship among discharge,biomass and Manning's coefficient through a calibration approach

The subject of environmental engineering is currently of great interest. Field experiments as well as numerical models have proven their worth in this research field. An introduction to hydrodynamic modelling, coupled to the modelling of vegetation biomass is described. The developed Strive (STream RIVer Ecosystem) model is set up in the Femme (‘Flexible Environment for Mathematically Modelling the Environment’) environment and has already proven its worth in a large number of calculations (De Doncker et al., 2006 , 2008b ). Discharges and water levels are modelled together with modelling of electrical conductivity (EC). Extensive measurement campaigns are carried out to collect a large number of observations and calibration of the model is based on this data set. Furthermore, calibration methods and the discussion of this process are displayed. As a result, it is seen that the developed Strive model can model both, hydrodynamic and ecological processes, in an accurate way. The work highlights the importance of detailed determination of Manning's coefficient, dependent on discharge and amount of biomass, as an important calibration parameter for accurate modelling. Copyright © 2011 John Wiley & Sons, Ltd.     

A parameter allocation approach for flow simulation using the WetSpa-Python model

Hydrologic models are simplified representations of natural hydrologic systems. Since these models rely on assumptions and simplifications to capture some aspects of hydrological processes, calibration of parameters is unavoidable. However, utilizing the philosophy of a recent modelling framework proposed by Bahremand (2016), we show how calibration of most model parameters can be avoided by allocating or presetting these parameters utilizing knowledge gained from sensitivity analyses, field observations and a priori specifications as a part of a parameter allocation procedure. This paper details the simulation of daily river flow of the Shemshak-Roudak watershed performed using the Python version of the WetSpa model. The WetSpa-Python model is a distributed model of hydrological processes applied at the watershed scale. The model was applied to the Shemshak-Roudak watershed of Iran with parameter allocation. Model calibration involved only two parameters. Straightforward methods were proposed for allocating model parameters, including three baseflow-related parameters and the determination of maximum active groundwater storage using a mass curve technique. Also, the Budyko curve was used to constrain a correction factor for potential evapotranspiration. The WetSpa-Python model was extended to include the influence of snowmelt. A failure to include snow in the hydrological processes of the WetSpa-Python model creates a significant discrepancy between the observed and simulated hydrographs during the spring. The results of daily simulations for 12 years (2002–2014) are in good agreement with observations of discharge (Kling-Gupta Efficiency = 0.84). These results demonstrate that it is feasible to simulate hydrographs with limited calibration given a knowledge of hydrological processes and an understanding of relationships between catchment characteristics and model parameters.     

Differential calibration of seismometers for measurement of rotation and strain

A method of correcting the seismometers’ responses discrepancy for differential measurements of strains and rotations in the seismic far field is proposed. The method concerns differential calibration of the whole seismometers’ array by electric current. A model of corrective filtering of the obtained differential signals in the Z domain is given. Two methods of the filter parameters’ estimation are introduced; they are based on the seismometers response to the calibration. A practical test of the methods — an analysis of a recorded seismic event — is added. Significant reduction of differences between simultaneous seismic recordings was obtained, which is interpreted as cleaning of differential signal from spurious elements.     

WACALIB version 3.3 — a computer program to reconstruct environmental variables from fossil assemblages by weighted averaging and to derive sample-specific errors of prediction

A computer program for reconstructing environmental variables (e.g. lake-water pH) from fossil assemblages (e.g. diatoms) by weighted averaging regression and calibration is described. The estimation of sample-specific errors of prediction by bootstrapping is outlined. The program runs on IBM-compatible personal computers.     

基于GIS甘肃中南部滑坡泥石流活动强度评价

以甘肃中南部为研究区,采用GIS、MATLAB、FUZZY相结合的评价方法,收集筛选评价指标数据,基于GIS进行数据处理、转换,将各层对应的2 km×2 km栅格数据转入MATLAB,建立成因性指标与滑坡泥石流活动强度的模糊隶属关系,基于GIS进行空间分析,确定评价指标划分等级,设计不同权重方案,在MATLAB中编程试算,试算结果用重点(样)区特征性数据所反映的强度大小与相对等级,进行拟合检验与灵敏性检验,进一步调整指标等级与权重参数,最终得到符合成因机制的滑坡泥石流活动强度评价等级分布。结果表明该评价方法高效实用、精度高,可以进行高分辨率区域评价、区域仿真模拟、区划等工作。     

海洋仪器计量检定校准数据处理系统

随着海洋仪器在海洋调查、海洋监测、海洋科研等领域的广泛应用,开展海洋仪器的计量检定校准工作成为了国家海洋计量站最基本的业务工作之一。“海洋仪器计量检定校准数据处理系统”是专门为海洋仪器计量检定、校准数据的处理而设计的软件系统,文章详细介绍了该系统的结构和功能。