基于四叉树算法的POI分级优化显示方法研究

为了使"天地图"中大数据量、高密度的POI数据在各显示比例下达到清晰易读的表达效果,本文在考虑POI权重属性的情况下,提出了一种基于四叉树算法进行自动过滤的方法,达到各级比例尺优化显示的效果,并通过实例验证该方法的可行性、稳定性,达到了对POI数据高效过滤和图面表达美观的双重效果。     

基于CART集成学习的城市不透水层百分比遥感估算

利用Landsat ETM^＋遥感数据，提出了一种基于CART集成学习的ISP遥感亚像元估算方法，将Boosting重采样技术引入CART分析中，用于提高ISP估算的精度。实验结果表明，该方法的ISP估算性能优于传统的单一CART学习算法，从ETM^＋影像中估算的ISP值与真实值之间的相关系数达到0．91，平均偏差为11．16％。     

花岗岩类土质边坡工程特性及加固方法研究

华南、华东南地区具有厚度可达上百米的花岗岩风化残积层。高等级公路、铁路的规模建设在该地区形成了大量的花岗岩类土质高边坡。深入认识该类边坡的工程特性并提出有效的针对性边坡加固方法,对该地区公路、铁路的安全建设和正常运营具有重要意义。为了更有效指导该类边坡的稳定性分析及边坡设计,本文深入调查分析了广东和广西境内4条高等级公路沿线的44处花岗岩类土质边坡特征及其稳定性,认为控制该类边坡稳定性的因素主要有:土体的均匀性、岩脉(墙)及花岗岩球状硬核的分布情况、坡体中保留的结构面是否对坡体稳定性起控制作用。继而依据这些因素把花岗岩类土质边坡划分为岩脉(墙)隔挡型边坡、网状结构型边坡、外倾结构型边坡、浮石型边坡4种类型。深入分析了每种类型边坡的坡体结构特征、稳定特性,针对性地提出了边坡稳定性分析中应重点考虑的因素。认为花岗岩类土质边坡的土质及坡体结构特征,造成了该类边坡开挖临时自稳性较好,但具有较强的开挖卸荷效应和较弱的抗冲刷能力。最后针对每种类型的花岗岩类土质边坡,提出了相应的设计方案建议。基于花岗岩类土质边坡良好的临时自稳性,认为可进行陡开挖强支护设计,同时强调逐级开挖逐级支护、加强坡面防冲刷、边坡护脚及压顶、边坡截排水等设计建议。     

高原边坡复杂地形下短时强降水的云型特征分类

利用逐时雨量资料、常规高低空观测资料及FY-2卫星云图,对2010—2015年5—9月甘肃省高原边坡复杂地形下76次短时强降水过程个例的天气形势配置及卫星云图演变特征进行统计分析。结果表明,与甘肃省短时强降水过程相关的特征云型共有6类:副热带高压边沿型、逗点云型、冷锋前部型、冷锋尾部与南亚高压东侧叠置型、冷涡后部型、弱冷锋前部椭圆形MαCS型。其中,副热带高压边沿型、冷锋前部型、弱冷锋前部椭圆形MαCS型与低层暖平流强迫有关。逗点云型、冷锋尾部与南亚高压东侧叠置型主要受高低空冷暖平流强烈交汇影响。冷涡后部型是高空冷平流强迫下形成。冷锋尾部与南亚高压东侧叠置型具有较好的预报指示意义。     

Shape indexes for semi-automated detection of windbreaks in thematic tree cover maps from the central United States

Windbreaks are an important ecological resource across the large expanse of agricultural land in the central United States and are often planted in straight-line or L-shaped configurations to serve specific functions. As high-resolution (i.e., <5 m) land cover datasets become more available for these areas, semi- or fully-automated methods for distinguishing windbreaks from other patches of trees are needed for use with thematic raster datasets. To address this need, we created three shape indexes: a morphology-based index that we have named the Straight and Narrow Feature Index (SNFI), a windbreak sinuosity index, and an area index indicating the occupied fractional area of a bounding box. The indexes were tested in two study areas: (1) a riparian area dominated by sinuous bands of trees but mixed with row crop agriculture and (2) an agricultural area with a mix of straight-line and L-shaped windbreaks. In the riparian area, a Kruskall–Wallis rank sum test indicated class differences for all three indexes, and pairwise comparisons indicate windbreaks and riparian trees are separable using any of the three indexes. SNFI also produced significant differences between windbreaks oriented in different directions (east–west vs. north–south). In the agricultural area, the Kruskall–Wallis rank sum test indicated differences between classes for all three indexes, and pairwise comparisons show that all class pairs have significant differences for at least one index, with the exception of L-shaped windbreaks vs. non-windbreak tree patches. We also used classification trees to objectively assign representative samples of tree patches to classes using both single indexes and multiple indexes. Classes were correctly assigned for more than 90% of the samples in both the riparian and agricultural study areas. In the riparian area, combining indexes did not improve accuracy compared to using SNFI alone, whereas in the agricultural area, combining the three indexes produced the best result. Thematic datasets derived from high-resolution imagery are becoming more available, and extracting useful information can be a challenge, partly due to the large amount of data to assess. Calculating the three shape indexes presented can assist with efficient identification of candidate windbreaks and as such, hold good promise for value-added analysis of tree function in the central United States.     

Integration of high-resolution imagery and LiDAR data for object-based classification of urban area

This paper investigates the synergistic use of high-resolution multispectral imagery and Light Detection and Ranging (LiDAR) data for object-based classification of urban area. The main contribution of this paper is the development of a semi-automated object-based and rule-based classification method. In the implemented approach, the diverse knowledge about land use/land cover classes are transformed into a set of specialized rules. Further, this paper explores supervised Gaussian Mixture Models for classification, which have been primarily used for unsupervised classification. The work is carried out on test data from two different sites. Contribution of the LiDAR data resulted in a significant improvement of overall Kappa. Accuracy assessment carried out for aforementioned classification methods shows higher overall kappa for both the study sites.     

基于ENVI 的唐山湾三岛土地利用遥感分类方法的比较分析

对唐山湾三岛2010年10月10 m分辨率的SPOT5多光谱数据源,采用不同分类方法进行识别和判断,并对比不同分类器在遥感影像分类中的应用效果和分类精度。有针对性地探究海岛土地利用遥感分类过程中不同方法的优劣,获取最适于岛陆地区土地利用的遥感分类方法。根据土地利用现状分类标准(GB/T21010-2007)和海岛陆域土地利用类型划分的相关规定,将唐山湾三岛主要分为滩涂、裸地、林地、草地、居住区、内陆水体和潮间带(潮水覆盖区)6类。并分别构建结合人为控制的非监督分类、监督分类和基于专家知识的决策树分类系统,参照更高分辨率影像、先验知识和野外调查资料,评价分类结果与实地调查结果的吻合程度,最终通过总体分类精度和Kappa系数等指标对各分类器精度进行评价和对比分析。     

Conservation status of New Zealand freshwater fish, 2009

The threat status of 74 freshwater and estuarine fish present in New Zealand was determined. Fifty-one native taxa were ranked of which 67% were considered Threatened or At Risk. A single species was classified as Extinct, the New Zealand grayling, which has not been observed since the 1920s. Four taxa were classified in the highest threat category, Nationally Critical, and a further 10 taxa as Threatened (Nationally Endangered or Nationally Vulnerable). Twenty taxa were ranked in the At Risk group with the majority ranked as Declining. Endemic galaxiids (Galaxiidae) dominated the Threatened and At Risk taxa. The majority (68%) belonged to the Galaxias genus, comprising 81% of recognised taxa in this genus and all five species in the genus Neochanna were also ranked as Threatened or At Risk. In addition to 51 native taxa, a further three fish species were considered colonists and 20 introduced species were classified as naturalised, although two of these are considered rare. The majority of the Threatened species occur in the Canterbury and Otago regions where a suite of rare non-migratory galaxiids exist. Threat mechanisms that were identified as causal in the decline of freshwater fish species were the impact of introduced fish species, declining water quality, effects of water abstraction, loss of habitat via land-use change and land-use activities, and river modifications.     

Automated multi-scale classification of the terrain units of the Jiaxie Guyots and their mineral resource characteristics

Given the advances in satellite altimetry and multibeam bathymetry, benthic terrain classification based on digital bathymetric models (DBMs) has been widely used for the mapping of benthic topographies. For instance, cobalt-rich crusts (CRCs) are important mineral resources found on seamounts and guyots in the western Pacific Ocean. Thick, plate-like CRCs are known to form on the summit and slopes of seamounts at the 1 000–3 000 m depth, while the relationship between seamount topography and spatial distribution of CRCs remains unclear. The benthic terrain classification of seamounts can solve this problem, thereby, facilitating the rapid exploration of seamount CRCs. Our study used an EM122 multibeam echosounder to retrieve high-resolution bathymetry data in the CRCs contract license area of China, i.e., the Jiaxie Guyots in 2015 and 2016. Based on the DBM construted by bathymetirc data, broad- and fine-scale bathymetric position indices were utilized for quantitative classification of the terrain units of the Jiaxie Guyots on multiple scales. The classification revealed four first-order terrain units (e.g., flat, crest, slope, and depression) and eleven second-order terrain units (e.g., local crests, depressions on crests, gentle slopes, crests on slopes, and local depressions, etc.). Furthermore, the classification of the terrain and geological analysis indicated that the Weijia Guyot has a large flat summit, with local crests at the southern summit, whereas most of the guyot flanks were covered by gentle slopes. “Radial” mountain ridges have developed on the eastern side, while large-scale gravitational landslides have developed on the western and southern flanks. Additionally, landslide masses can be observed at the bottom of these slopes. The coverage of local crests on the seamount is ~1 000 km2, and the local crests on the peak and flanks of the guyots may be the areas where thick and continuous plate-like CRCs are likely to occur.