利用数学形态学的遥感影像水系提取方法

针对目前遥感水系提取存在的问题,提出了一种基于数学形态学的遥感影像水系提取方法。该方法在光谱模式识别提取水体信息的基础上,利用数学形态学方法将提取的水体结果进行断线连接、去噪及细化等处理,从而得到连续的水系。以Landsat ETM+影像为例进行了实验,结果表明,该方法可以提取连续、完整的水系;且提取的水系精度与现势性均优于国家测绘局发布的1∶25万数字线划图(DLG)水系。     

A novel mathematical morphology based algorithm for shoreline extraction from satellite images

Abstract

Shoreline extraction is fundamental and inevitable for several studies. Ascertaining the precise spatial location of the shoreline is crucial. Recently, the need for using remote sensing data to accomplish the complex task of automatic extraction of features, such as shoreline, has considerably increased. Automated feature extraction can drastically minimize the time and cost of data acquisition and database updating. Effective and fast approaches are essential to monitor coastline retreat and update shoreline maps. Here, we present a flexible mathematical morphology-driven approach for shoreline extraction algorithm from satellite imageries. The salient features of this work are the preservation of actual size and shape of the shorelines, run-time structuring element definition, semi-automation, faster processing, and single band adaptability. The proposed approach is tested with various sensor-driven images with low to high resolutions. Accuracy of the developed methodology has been assessed with manually prepared ground truths of the study area and compared with an existing shoreline classification approach. The proposed approach is found successful in shoreline extraction from the wide variety of satellite images based on the results drawn from visual and quantitative assessments.     

现代植物炭屑形态的初步分析及其古环境意义*

通过对23种现代植物炭屑的观察、测量以及对草本、木本炭屑模拟破碎试验后的测量统计发现:现代植物炭屑形态根据其长宽比(L/W)和形态特征可以分为3个类型:1)草本型炭屑,L/W最大,平均为10.2±1.3, 呈长-薄条型、针型、簇纤维型,边缘及断口截然,棱角分明,有些具有气孔构造,很少有不规则的形态出现; 2)木本型炭屑(灌木+乔木),L/W较小,平均3.1±0.2,多呈方~长方型或立方体型,边缘多参差不齐,有些横向断口有粗大木纤维露出,相对致密; 3)阔叶类植物叶片炭屑,L/W最小,平均1.7±0.1,薄片状、网状,絮状,易碎。进一步通过对6个典型草原和森林表土样品的实验室分析,发现现代土壤中的炭屑颗粒大小相对现代植物炭屑颗粒大小总体有所减小,但草原土壤中炭屑长宽比相对森林土壤炭屑仍然较大,土壤中炭屑形态和部分结构鉴别特征仍能保留。表明L/W值与炭屑结构特征可以用来区分多数草本与木本植物炭屑。在此基础上,通过对黄土高原渭南剖面S₁以来不同层位12个地层样品的炭屑形态分析,初步研究了不同草本、木本植物炭屑形态变化的特点和环境意义。     

Neural network modelling of planform geometry of headland-bay beaches

The shoreline of beaches in the lee of coastal salients or man-made structures, usually known as headland-bay beaches, has a distinctive curvature; wave fronts curve as a result of wave diffraction at the headland and in turn cause the shoreline to bend. The ensuing curved planform is of great interest both as a peculiar landform and in the context of engineering projects in which it is necessary to predict how a coastal structure will affect the sandy shoreline in its lee. A number of empirical models have been put forward, each based on a specific equation. A novel approach, based on the application of artificial neural networks, is presented in this work. Unlike the conventional method, no particular equation of the planform is embedded in the model. Instead, it is the model itself that learns about the problem from a series of examples of headland-bay beaches (the training set) and thereafter applies this self-acquired knowledge to other cases (the test set) for validation. Twenty-three headland-bay beaches from around the world were selected, of which sixteen and seven make up the training and test sets, respectively. As there is no well-developed theory for deciding upon the most convenient neural network architecture to deal with a particular data set, an experimental study was conducted in which ten different architectures with one and two hidden neuron layers and five training algorithms – 50 different options combining network architecture and training algorithm – were compared. Each of these options was implemented, trained and tested in order to find the best-performing approach for modelling the planform of headland-bay beaches. Finally, the selected neural network model was compared with a state-of-the-art planform model and was shown to outperform it.     

乌鲁木齐霾天气PM10单颗粒物理化学特征

为了解乌鲁木齐冬季污染天气形成过程中大气颗粒物化学组分的变化,探讨霾天气快速形成的主要原因,应用扫描电镜/X射线能谱仪(SEM/EDX)对2013年2月乌鲁木齐东南郊一次典型霾天和正常天气所采集的大气颗粒物(PM₁₀)样品进行了微观形貌和化学组成的对比分析。结果表明:伴随着霾形成过程细粒子浓度呈现急剧上升趋势,PM_1.0/PM₁₀比值高达0.77。SEM/EDX观测显示,霾天形成前后,PM₁₀的形态结构和元素组成存在较明显的差异,霾天规则的石膏颗粒占规则颗粒的71.1%,明显高于正常天气,表明大气颗粒物的硫化现象比较普遍,大量硅铝酸盐飞灰说明采样点周边有较明显的燃煤源输送;二次无机颗粒组成主要为硫酸盐颗粒,由正常天气的16.1%增加到24.6%,高浓度硫酸盐与乌鲁木齐东南郊此次霾形成有密切的联系。     

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.     

Lake Floor Morphology and Sediment Architecture of Lake Torneträsk,Northern Sweden

Here we present datasets from a hydroacoustic survey in July 2011 at Lake Torneträsk, northern Sweden. Our hydroacoustic data exhibit lake floor morphologies formed by glacial erosion and accumulation processes, insights into lacustrine sediment accumulation since the beginning of deglaciation, and information on seismic activity along the Pärvie Fault. Features of glacial scouring with a high‐energy relief, steep slopes, and relative reliefs of more than 50 m are observed in the large W‐basin. The remainder of the lacustrine subsurface appears to host a broad variety of well preserved formations from glacial accumulation related to the last retreat of the Fennoscandian ice sheet. Deposition of glaciolacustrine and lacustrine sediments is focused in areas situated in proximity to major inlets. Sediment accumulation in distal areas of the lake seldom exceeds 2 m or is not observable. We assume that lack of sediment deposition in the lake is a result of different factors, including low rates of erosion in the catchment, a previously high lake level leading to deposition of sediments in higher elevated paleodeltas, tributaries carrying low suspension loads as a result of sedimentation in upstream lakes, and an overall low productivity in the lake. A clear off‐shore trace of the Pärvie Fault could not be detected from our hydroacoustic data. However, an absence of sediment disturbance in close proximity to the presumed fault trace implies minimal seismic activity since deposition of the glaciolacustrine and lacustrine sediments.     

A new species of Plaxiphora (Mollusca: Polyplacophora) from southern New Zealand

Plaxiphora boydeni n.sp. from wave‐exposed rocky shores of southern New Zealand is described and illustrated. This is the first published record of the genus from the New Zealand mainland. P. boydeni is readily distinguished from the 2 other New Zealand species of the genus, which occur in the subantarctic region, by the absence of bristle‐tufts on the girdle.