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41.
Geographic Object-Based Image Analysis (GEOBIA) is becoming more prevalent in remote sensing classification, especially for high-resolution imagery. Many supervised classification approaches are applied to objects rather than pixels, and several studies have been conducted to evaluate the performance of such supervised classification techniques in GEOBIA. However, these studies did not systematically investigate all relevant factors affecting the classification (segmentation scale, training set size, feature selection and mixed objects). In this study, statistical methods and visual inspection were used to compare these factors systematically in two agricultural case studies in China. The results indicate that Random Forest (RF) and Support Vector Machines (SVM) are highly suitable for GEOBIA classifications in agricultural areas and confirm the expected general tendency, namely that the overall accuracies decline with increasing segmentation scale. All other investigated methods except for RF and SVM are more prone to obtain a lower accuracy due to the broken objects at fine scales. In contrast to some previous studies, the RF classifiers yielded the best results and the k-nearest neighbor classifier were the worst results, in most cases. Likewise, the RF and Decision Tree classifiers are the most robust with or without feature selection. The results of training sample analyses indicated that the RF and adaboost. M1 possess a superior generalization capability, except when dealing with small training sample sizes. Furthermore, the classification accuracies were directly related to the homogeneity/heterogeneity of the segmented objects for all classifiers. Finally, it was suggested that RF should be considered in most cases for agricultural mapping. 相似文献
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Quantification of forest degradation in monitoring and reporting as well as in historic baselines is among the most challenging tasks in national REDD+ strategies. However, a recently introduced option is to base monitoring systems on subnational conditions such as prevalent degradation activities. In Tanzania, charcoal production is considered a major cause of forest degradation, but is challenging to quantify due to sub-canopy biomass loss, remote production sites and illegal trade. We studied two charcoal production sites in dry Miombo woodland representing open woodland conditions near human settlements and remote forest with nearly closed canopies. Supervised classification and adaptive thresholding were applied on a pansharpened QuickBird (QB) image to detect kiln burn marks (KBMs). Supervised classification showed reasonable detection accuracy in the remote forest site only, while adaptive thresholding was found acceptable at both locations. We used supervised classification and manual digitizing for KBM delineation and found acceptable delineation accuracy at both sites with RMSEs of 25–32% compared to ground measurements. Regression of charcoal production on KBM area delineated from QB resulted in R2s of 0.86–0.88 with cross-validation RMSE ranging from 2.22 to 2.29 Mg charcoal per kiln. This study demonstrates, how locally calibrated remote sensing techniques may be used to identify and delineate charcoal production sites for estimation of charcoal production and associated extraction of woody biomass. 相似文献
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针对造成湖南省特大暴雨过程的"碧利斯"和"圣帕"两次台风,利用气象、水文加密观测资料及NCEP再分析资料,结合中尺度数值预报模式AREM的模拟结果,对它们独特的水汽场特征进行了对比分析.结果表明:这两次台风的共同特点是有两条主要水汽输送通道,即与西南季风相联系的偏南风水汽通道和与台风低压环流相联系的偏北风水汽通道;凝结降水的水汽主要来源于低层风场辐合和水汽平流,并通过局地垂直运动再将其输送到中高层;在湘东南强降水区上空始终存在强的水汽水平辐合和水汽垂直输送,比较而言,"圣帕"台风暴雨区上空水汽通量更强,但水汽通量辐合强度却小于"碧利斯"台风,水汽辐合层也不及后者深厚,但前者由于自身旋转性强,低压环流中心南部的切变较长时间维持,并自东向西转动,使得强降水持续时间更长,过程雨量更大,影响范围也更大."碧利斯"水汽主要源地较"圣帕"更加偏南,水汽辐合更强,与南海季风的相互作用更显著,降水时段集中,局部地区短时间内的降雨强度甚至超过了"圣帕". 相似文献
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面向对象影像分类中基于最大化互信息的特征选择 总被引:1,自引:0,他引:1
高分辨率影像面向对象分割后产生了大量的光谱、形状以及纹理特征,如何抽取出最佳特征子集是遥感影像识别的重要问题.本文利用最大化互信息统计独立准则抽取最优特征子集,提高了面向对象遥感影像分类精度.基本过程包含以下3个方面:首先,利用eCoginition软件对高分辨遥感影像进行对象分割;然后,基于互信息最大关联、最小冗余准则(mRMR)获取优选的特征子集;最后,基于支持向量机分类器完成影像分类.以福建省漳州市QuickBird数据为例的实验表明,该方法能够有效提高遥感影像的分类精度,平均误分率降低了约4%. 相似文献
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以江阴市城乡一体化现代地籍管理信息系统为例,在综合分析了当前地籍数据分类和要素编码标准的现状后,提出了城乡一体化模式下现代地籍数据的分类和要素编码标准,最后结合实际的项目应用,总结了该标准的优缺点. 相似文献
47.
This paper presents the overall sinkhole distributions and conducts hypothesis tests of sinkhole distributions and sinkhole formation using data stored in the Karst Feature Database (KFD) of Minnesota. Nearest neighbor analysis (NNA) was extended to include different orders of NNA, different scales of concentrated zones of sinkholes, and directions to the nearest sinkholes. The statistical results, along with the sinkhole density distribution, indicate that sinkholes tend to form in highly concentrated zones instead of scattered individuals. The pattern changes from clustered to random to regular as the scale of the analysis decreases from 10–100 km2 to 5–30 km2 to 2–10 km2. Hypotheses that may explain this phenomenon are: (1) areas in the highly concentrated zones of sinkholes have similar geologic and topographical settings that favor sinkhole formation; (2) existing sinkholes change the hydraulic gradient in the surrounding area and increase the solution and erosional processes that eventually form more new sinkholes. 相似文献
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利用山水特色,重现福州山水城市 总被引:2,自引:0,他引:2
山、水和绿化是构成福州古城山水的基本要素。在城市不断扩展的过程中,由于对城市山水,尤其是内河的开发和利用不够合理,保护不够得力,使福州失去了山水城市的特色。通过以福州城市山水现状的调查和分析,认为必须从旅游和生态的角度出发,增强环境意识,恢复城市内河活力,加强城市绿化,建设好“三山”,以提高城市环境质量,重现福州的山水城市风貌。 相似文献