Mapping Wetland Areas Using Landsat-Derived NDVI and LSWI: A Case Study of West Songnen Plain,Northeast China

Increasing interest in wetlands for environmental management requires an understanding of the location, spatial extent, and configuration of the resource. The National Wetlands Inventory is the most commonly used data source for this information. However, its accuracy is limited in some contexts, such as agricultural and forested wetlands. An large number of studies have mapped wetlands worldwide from the perspective of land use and land cover change. However, information on the actual wetland planting areas annually is limited, which greatly impacts ongoing research. In this case study of the West Songnen Plain, we developed a simple algorithm for the quick mapping of wetlands by utilizing their unique physical features, such as annual display of phenological land-cover change of exposed soils, shallow flooding water, and plants from multi-temporal Landsat images. Temporal variations of the Normalized Difference Vegetation Index (NDVI) and Land Surface Water Index (LSWI) derived from Landsat images in 2010 for wetlands at different growth stages were analyzed. Results show that during the ante-tillering phase, the NDVI value (above zero) is lower than the LSWI value of paddies because of flooding of shallow water; during the reproductive and ripening phases, the NDVI value is higher than the LSWI value (above zero); and during the post-harvest wetland planting phase, the NDVI value is still higher than the LSWI value, but the LSWI value is negative. Wetland areas can be detected using one or two images in the optimum time window. The algorithm based on the difference of NDVI and LSWI values derived from Landsat images was used to extract the actual wetland planting area. Validated alongside statistical data, the algorithm showed high accuracy. Therefore, this algorithm highlights the unique features of wetlands and can help in mapping the actual wetland area annually on a regional scale. Results further indicate that the new method has a classification accuracy of 92 %. In comparison, two traditional methods based on Landsat-7/ETM registered accuracy rates of only 83 % and 87 % respectively.     

Statistical diagnosis and gross error test for semiparametric linear model

This paper systematically studies the statistical diagnosis and hypothesis testing for the semiparametric linear regression model according to the theories and methods of the statistical diagnosis and hypothesis testing for parametric regression model. Several diagnostic measures and the methods for gross error testing are derived. Especially, the global and local influence analysis of the gross error on the parameter X and the nonparameter s are discussed in detail; at the same time, the paper proves that the data point deletion model is equivalent to the mean shift model for the semiparametric regression model. Finally, with one simulative computing example, some helpful conclusions are drawn.     

Measurement of similarity for spatial directions between areal objects

Similarity for spatial directions plays an important role in GIS. In this paper, the conventional approaches are analyzed. Based on raster data areal objects, the authors propose two new methods for measuring similarity among spatial directions. One is to measure the similarity among spatial directions based on the features of raster data and the changes of distances between spatial objects, the other is to measure the similarity among spatial directions according to the variation of each raster cell centroid angle. The two methods overcome the complexity of measuring similarity among spatial directions with direction matrix model and solve the limitation of small changes in direction. The two methods are simple and have broader applicability.     

数字哈密地理信息公共服务平台设计与实现

以数字哈密地理信息公共服务平台建设为例,总结研究了地理信息公共服务平台设计和建设方案。通过信息提取、扩充、重组等整合处理建立适应信息时代要求的公共数据集,开发具备信息集成、浏览查询、统计分析、互联互通以及二次开发等功能的分布式服务系统,配置完善的软件、硬件和网络支撑环境,建成权威的地理信息公共平台,实现地理空间信息和其他专题信息的实时交换和共享,服务和推进政府及各部门的信息化建设。     

GLONASS pseudorange inter-channel biases considerations when jointly estimating GPS and GLONASS clock offset

GLONASS clock offset estimation is affected by the inter-channel biases (ICBs) caused by frequency division multiple access technique. The effect of ICBs on joint GPS/GLONASS clock offset estimation is analyzed. An efficient approach for joint estimation of GPS/GLONASS satellite clock offset is applied to the generation of 30-s clock offset products. During the estimation, the following three ICB handling strategies were tested: calculating ICBs for each GLONASS signal channel, calculating ICBs for each GLONASS satellite and neglecting ICBs. The behavior of ICBs under different strategies was statistically stable. Subsequently, the clock offset products using different ICB strategies were evaluated. The evaluation shows that consideration of the ICB is important when estimating the clock offset. Furthermore, estimating one ICB for each GLONASS satellite is better than estimating one for each GLONASS signal channel because, with the former strategy, the clock offset products behave more smoothly and have higher accuracy compared with products from the International GNSS Service Analysis Center. In addition, precise point positioning, using clock offsets based on one ICB for each GLONASS satellite, has the highest positioning accuracy.     

基于SVM的多源遥感影像面向对象建筑物提取方法

在分析支持向量机(Support Vector Machine,SVM)分类技术和机载激光雷达(LIDAR)数据、航空影像特征的基础上,提出了基于SVM的LIDAR数据和航空影像的面向对象建筑物提取方法。结果表明,该方法充分利用了多源影像的互补信息,能够得到更高的信息提取精度,准确而快速地更新地理空间数据库,是一种有效的面向对象建筑物提取方法。     

基于VRS的GPS测量误差分析

系统误差包括卫星轨道误差、卫星钟差、接收机钟差及大气折射误差等。是GPS测量的主要误差源。但系统误差通常可以采用适当的方法来减弱或消除,如建立误差改正模型对观测值进行改正,或选择良好的观测条件,采用适当地观测方法,进行线性差分等.本文介绍了基于VRS的GPS测量要解决的一个主要问题即在系统运行中产生的各种误差进行改正,使之减小或者消除。并就影响VRS精度的各种误差予以分析     

测绘在新农村建设中存在的问题和对策

新农村建设也像城市一样，必须有测绘为其提供服务与保障。本文重点对测绘在新农村建设中存在的突出问题进行了深入分析，并就如何进一步推进新农村建设测绘工作提出了建议和对策。     

石油物探测量中采用GPS RTK技术不利因素的分析

高精度GPS实时差分(RTK)定位技术是目前各领域最广泛使用的测量技术之一,尤其是在石油物探测量中,提高了测量成果的精度,满足了三维和高分辨率地震勘探的要求,提高了作业速度,减轻了测量人员的劳动强度,从而深受人们的青睐。本文从RTK基准站选择、转换参数求取、数据链传输、流动站作业过程等方面,探讨了石油物探测量中对RTK技术的不利因素及处理方法。