Assessing urban growth and rural land use transformations in a cross-border situation in Northern Namibia and Southern Angola

The Okavango catchment is a hot spot of accelerating land use change. In particular, climate predictions, demographic developments and a growing utilization of ecosystem services and functions are expected to increase pressure on resources and land. Land use conflicts, the sustenance of precarious livelihoods, deforestation of woodland savannahs, upstream–downstream water issues and human–wildlife conflicts are among the processes that are characteristic of policy and management challenges in the region. In the Eastern and Western Kavango regions of Namibia and the Cuando-Cubango province of Angola, a unique cross-border situation exists that allows assessing how the combination of local traditions, regional land management and national policies determines spatial patterns of land use and land cover transformation processes.To map major land use types and change processes we used a set of multi-temporal Landsat-5 TM and Landsat-7 ETM+ data sets, support vector machine (SVM) classification and iterative spectral mixture analysis (ISMA) on images covering the period from 1990 to 2010. Integrating satellite imagery with literature reviews, interviews, census and household survey data, we assessed the contrasting development of resource utilization on both sides of the Okavango River. We investigated if and how policies and regulations at different levels drive land use decisions, and how these decisions manifest spatially.We found a strong and interconnected urban growth on both sides of the river. The area around Rundu has constantly been evolving to become Namibia's second largest city, also functioning as a hub of development and transborder commerce with opposing Calai. This trend was found to affect adjacent settlement areas and cause widespread conversion of woodland savannahs to agricultural land or their utilization for timber extraction. The conversion of woodland savannah to arable land was by far the dominant land use change process on both sides of the river, with a total conversion area of 460 km² (Namibia) and 293 km² (Angola) observed during the observation period. Strong spatial change gradients occurred in relation to determining factors, such as accessibility, proximity to water, urban centres, etc., while relations to settlements where less obvious. Assessing results by country illustrated the difference in land use intensity and resource consumption between Angola and Namibia, which relate directly to historical developments, with a long period of stability in Namibia standing opposed to the recent and ongoing recovery from civil war in Angola. These are added to by statutory and traditional policy frameworks, the national endowment with natural capital (e.g. oil, uranium, diamonds, zinc) and the integration into global markets, which strongly affects national economies of both countries at large.Underlying land use decisions were found to be largely driven by individualized perspectives on growth ideologies, consumerism and wealth-aspirations connected to globalization processes. However, at present the result of these perspectives is still mainly a small-structured conversion to rainfed agriculture as a component of subsistence strategies of local livelihoods, and thus stands opposed to other regions of the world, where change processes are much more driven by large companies or follow national regulations and result in more intensive uses.     

Comparison of land use change in payments for environmental services and National Biological Corridor Programs

Costa Rica established the National Biological Corridor Program in 2006. Under the National Biological Corridor Program, the long-running Payment for Environmental Services Program was newly prioritized into biological corridors throughout the country. The National Biological Corridor Program caused a nationwide spatial shift in placement of payments for environmental services throughout Costa Rica. We classified ASTER 15-m resolution imagery in a central Costa Rica corridor connecting the eastern and western protected areas networks to analyze the change in forests during the National Biological Corridor Program with its targeted payments for environmental services effort. We used object-based classification methods, and compared land cover changes over an initial four-year period of corridor policy enactment. We calculated the changes within PES properties and outside of PES regions, and we also calculated forest patch metrics during the same time period. Results indicate a decline in forest cover over the study period, along with an increase in urban and pasture land covers, with higher change and loss of forest centered inside of the biological corridor, near the construction area for the new San Carlos highway, and within eastern pasture areas. We also saw a higher percentage of forest loss inside of the biological corridor area as compared to areas outside of the biological corridor. Forest loss was drastically less within current and historic PES properties, as compared to the overall study region. Across the entire study region, patch metrics show a decrease in the number of patches and a slight decrease in average patch size. These results suggest that current and past designation of PES prevents forest loss within PES properties while the current designation of priority conservation status via the National Biological Corridor Program is not increasing connectivity and forest conservation. This is shown by increased land use change and a decrease in forest associated with biological corridor designation. These results are antithetical to the goals of the National Biological Corridor Program.     

基于遥感数据的青海湖流域土地沙漠化评价研究

青海湖地区是我国青藏高原的生态脆弱区。我们利用遥感技术手段配合地面调查数据,建立适合青海湖流域的沙漠化评价指标体系,并对流域的沙漠化程度进行评价。结果显示,青海湖流域潜在沙漠化土地面积7497.45km~2,占研究区总面积的55.82%;发展中的沙漠化土地面积4569.81km~2,占研究区总面积的34.03%;强烈发展中的沙漠化土地面积546.41km~2,占研究区总面积的4.07%;严重沙漠化土地面积816.62km~2,占研究区总面积的6.08%。气候与土壤结构是青海湖流域土地沙化的主要原因。     

基于RBF神经网络的高光谱遥感影像降维及分类

高光谱遥感影像数据量大,针对该特点,为尽可能保留数据中有价值的信息,首先采用线性判别分析(Linear Discriminant Analysis,LDA)方法对高光谱遥感影像数据进行降维,接着应用径向基函数(Radial Basis Function,RBF)神经网络方法对其进行分类处理。实验结果表明,分类精度可达到70%以上,具有良好的分类效果,证明了该方法的可行性。     

杭州市区LUCC与社会经济的关系研究

土地是人类绝大部分活动的空间载体。人类的活动与土地利用和土地覆盖变化(Land Use/Cover Change,简称LUCC)息息相关。改革开放后,杭州市区LUCC较显著,与人口、经济发展、生活水平、交通运输等因子有着密切的联系。本文在对杭州市区遥感影像分类基础上,运用转移矩阵对其进行土地类型分析。结果表明各个阶段杭州市区建筑面积增加,大量耕地转化为建筑用地,在2000年后转化速度较快。这是杭州城市化的必然结果。通过主成分分析发现交通运输因子在各个因子间更具有代表性,但对各个LUCC进行逐步回归分析发现林地、水体的面积和人口的相关性较高,建筑、耕地的面积分别与城镇人均居住面积成高度的正、负相关。人口和人均居住面积是市区LUCC的关键因素。     

Deforestation and land tenure in Mexico: A response to Bonilla-Moheno et al.

Bonilla-Moheno et al. published an interesting paper on land tenure as a determinant of deforestation in Mexico, in Land Use Policy in 2013. In this review, we focus critically on the methodology used by the authors to reach two key conclusions. Firstly, we suggest that their use of coarse resolution MODIS EVI data to assess deforestation rates may have resulted in an erroneous conclusion, that forest area in Mexico is increasing rather than decreasing. This finding is contrary to official data and to other recent scientific assessments. Secondly, we question their conclusion that territories under the tenure of ‘comunidades indigenas’ are less likely to experience deforestation, and more likely to experience expansion of forest area, than those under ‘ejidal’ tenure. We believe that the sampling method, which involved the selection of municipalities with high concentrations of one particular type of tenure, and which eliminated the 60% of municipalities which contain mixed forms of tenure, biased the sample, particularly for the case of comunidades. The comunidades included in the sample are almost all found in a single region of the country, which may represent a special case. In reality comunidades are much more widespread through the country. Moreover we find that the explanation given by the authors for the relative success of comunidades in conserving their forests is not founded in data from any study of process at the local level.     

压缩感知的发展与应用

压缩感知（Compressed Sensing,CS）是近年来新兴的一种信号获取技术。沿着 CS理论的发展历程介绍了CS理论框架,给出了其严格的数学描述,着重讨论了对原始信号的 重构技术,最后介绍了一些可能的应用。     

GNSS-R海洋遥感技术浅议

GNSS-Reflection技术是以GPS等卫星导航系统的微波信号源进行遥感探测的前沿技术,在海洋环境监测中具有重要的应用前景。本文介绍了GNSS-R的基本工作原理,及其在海面高、海风、海冰监测中的具体应用,同时将GNSS-R方法和传统的微波雷达遥感进行了分析比较,以期对我国海洋遥感技术的发展和二代北斗的应用提供一定的参考。     

自动抠像技术与互动感应技术结合运用

在计算机信息处理技术快速发展的时代,我们通过现代计算机技术可以实现抠像技术、体感互动技术、图像实时处理技术的完美结合。既提高资源的利用效率,又增加了互动性、娱乐性。     

基于Landsat8数据的沙湖叶绿素a反演研究

本文以武汉沙湖水体为研究对象,以“3S”技术为支撑,基于Landsat 8遥感影像数据与实测水质数据,根据各波段反射率的相关性,分析与研究了遥感影像数据的适宜波段,采用回归分析的方法,建立适合沙湖水体的叶绿素a浓度遥感反演模型。反演结果表明,以第4波段建立的多项式回归反演模型效果较好,其平均误差为7.28%,Landsat 8影像数据能有效用于沙湖叶绿素a浓度的监测,在空间分布上也呈现一定的空间格局形态,并显示沙湖西北角(新生路泵站)污染相对严重,与沙湖实际情况基本吻合,因此将Landsat 8影像数据应用于内陆湖泊水体叶绿素a浓度反演具有一定的可行性。