The influence correction of boreal forest vegetation on SRTM data

The digital elevation model based on SRTM is very convenient for a wide range of studies but requires correction due to the influence of forest vegetation. The present study was conducted to analyse the effect of boreal forests on altitudes, aspects and slopes calculated from the SRTM. A DEM based on topographic maps at 1:100 000 scale was used as a reference. The linear regression analysis showed low data correlation in forested areas. The presence of different types of forests and felling in the woods leads to a complex distribution of deviations from the SRTM. A simple correction method was proposed, using a forest mask, built according to Landsat, and forest heights indicated on the topographic maps. After correction, the correlation coefficient between the altitudes increased by 0.05–0.14, the share of matching aspects by 1–4% and the share of matching slopes by 2–8%.     

Mapping rubber trees based on phenological analysis of Landsat time series data-sets

This study proposes a strategy for accurate mapping of rubber trees through the analysis of Landsat time series datasets. The phenological dynamics of rubber trees were derived from the Normalized Difference Vegetation Index (NDVI) to verify the three important phenological metrics of rubber trees; defoliation, foliation and their growing stages. A decade (2006–2015) ago, Landsat time series NDVIs were used to study the strength of relationship between rubber trees, evergreen trees and oil palm trees. Two important results that could discriminate these three types of vegetation were found; firstly, a weak relationship of NDVIs between rubber trees and evergreen trees during the defoliation period (r² = 0.1358) and secondly between rubber trees and oil palm trees during the growing period (r² = 0.2029). This analysis was verified using Support Vector Machine to map the distribution of the three types of vegetation. An accurate mapping strategy of rubber trees was successfully formulated.     

2012-2015年中缅油气管道重要节点土地利用/覆被时空变化分析

"中缅油气管道"是我国陆上第三大能源通道,该项目的建设将改变其沿线周边的土地利用/覆盖现状,同时对沿线地区的自然环境和社会经济发展产生重要影响。本文选取中缅油气管道沿线的国内11个重要节点和缅甸境内4个重要节点作为研究区,以2012年和2015年2期Landsat7 ETM+和Landsat8 OLI影像数据作为数据源,利用决策树分类算法提取2012年和2015年2期中缅油气管道沿线重要节点的土地利用/覆被信息,分析2012年和2015年2个时期的中缅油气管道沿线15个重要节点土地利用/覆被的时空变化。研究结果表明：①15个节点中,除德宏芒市、保山隆阳区、缅甸若开邦外,其他11个节点的土地覆被变化均在20%左右;②15个节点中,最主要的土地覆被变化为植被和裸土的相互转换,其次为其他土地覆被类型向建筑的转换;③由于中缅油气管道项目的辐射作用,带动当地经济发展,改变当地的经济作物结构,因此造成大量的植被和裸土的相互转换,并造成建筑用地需求增加,出现大量的其他地表覆被类型向建筑的转换。     

滇东南文山地区铝土矿遥感资源评价

滇东南铝土矿资源最为集中,但地质条件较复杂。使用传统遥感矿化蚀变信息提取方法效果欠佳。本文尝试通过进行羟基蚀变信息的提取确定铝土矿的靶区,取得较好的效果。     

Evolution of debris cover on glaciers of the Eastern Alps,Austria, between 1996 and 2015

Debris cover on glaciers is an important component of glacial systems as it influences climate–glacier dynamics and thus the lifespan of glaciers. Increasing air temperatures, permafrost thaw and rock faces freshly exposed by glacier downwasting in accumulation zones result in increased rockfall activity and debris input. In the ablation zone, negative mass balances result in an enhanced melt-out of englacial debris. Glacier debris cover thus represents a clear signal of climate warming in mountain areas. To assess the temporal development of debris on glaciers of the Eastern Alps, Austria, we mapped debris cover on 255 glaciers using Landsat data at three time steps. We applied a ratio-based threshold classification technique and analysed glacier catchment characteristics to understand debris sources better. Across the Austrian Alps, debris cover increased by more than 10% between 1996 and 2015 while glaciers retreated in response to climate warming. Debris cover distribution shows significant regional variability, with some mountain ranges being characterised by mean debris cover on glaciers of up to 75%. We also observed a general rise of the mean elevation of debris cover on glaciers in Austria. The debris cover distribution and dynamics are highly variable due to topographic, lithological and structural settings that determine the amount of debris delivered to and stored in the glacier system. Despite strong variation in debris cover, all glaciers investigated melted at increasing rates. We conclude that the retarding effects of debris cover on the mass balance and melt rate of Austrian glaciers is strongly subdued compared with other mountain areas. The study indicates that, if this trend continues, many glaciers in Austria may become fully debris covered. However, since debris cover seems to have little impact on melt rates, this would not lead to prolonged existence of debris-covered ice compared with clean ice glaciers.     

精河到伊宁公路沿线积雪及其影响

利用MODIS和Landsat TM/ETM+遥感数据,得出研究区的积雪面积,同时结合精伊公路规划图及地形图,分析了公路沿线可能存在风吹雪和雪崩的危险区,并提出相应的防治措施。结果表明:研究区近5年来11月到次年3月是积雪最丰富时期,9月、10月、4月和5月积雪较少。近5年来积雪呈增加趋势,最大积雪时间集中在2009—2010年积雪季。MODIS积雪数据精度在积雪面积越大时,精度越高;积雪面积越小时,精度越低。精伊公路东线走廊K60以上路段和西线走廊K100以上路段风吹雪对公路影响较大;精伊公路北段的雪崩的可能性很小;东线走廊K60～K77段和西线走廊K90～K110段有一定的雪崩灾害;西线走廊K58～K90段有较大的雪崩危害。并提出防治措施。     

TM/ETM+影像大气校正产品质量评价方法研究

对TM/ETM+的大气校正产品质量进行评价是改进影像质量的必要手段。提出采用已有高质量TM/ETM+表面反射率产品作为参考影像评价TM/ETM+的大气校正产品质量的方法。该方法设计了面向产品质量评价的影像光谱采样方案和多时相遥感影像PIFs(pseudo invariant features,PIFs)样本自动识别方法,能对多时相/季相TM/ETM+大气校正产品质量进行评价。试验表明该方法能准确识别PIFs地物,评价结果真实反映了遥感影像大气校正结果准确度。方法具有快速和低成本等特点,能开展规模化应用。     

采用高分辨率TM遥感数据对草原沙化治理工程进行生态效益评价

摘要本文以高分辨率TM遥感数据为基础,对位于浑善达克沙地境内的草原沙化治理工程采用遥感影像处理与定量分析和模拟相结合的方法,建立了草原沙化治工程生态效益快速评价体系。     

二型模糊集合在遥感影像土地利用分类中的应用

在遥感影像土地利用分类中,传统的布尔分类法只考虑地物光谱信息,用"是"与"非"的二值确定逻辑状态分类影像,当存在较多混合像元时,其不能满足一些实际应用的要求。模糊分类法综合了地物光谱特征、空间特征和对象的拓扑关系,对每个像元的归属用[0～1]的模糊度来表示,有效地解决了该问题。通过对研究区TM影像进行传统布尔法分类和模糊分类法分类的结果比较可知:对混合像元较多且波段较少的遥感影像土地利用分类,二型模糊集合分类能够适应用户不同精度需求,并能交互式输出结果。     

Crustal lineament control on magmatism and mineralization in northwestern Argentina: geological, geophysical, and remote sensing evidence

The relationship between long-lived deep crustal lineaments and the locations of magmatic centers and associated mineral deposits has been investigated in the Puna region of northwestern Argentina, through the analysis of regional aeromagnetic surveys, Landsat images, and geological information. The good exposure and excellent preservation of basement and supracrustal geology in this region makes it particularly suitable for such a study. At a regional scale, several contrasting magnetic domains are recognized, which correlate with crustal geology. Two basement domains are separated by a NNE-trending boundary, which is believed to correlate with a Paleozoic suture zone between the Pampia (to the southeast) and Arequipa–Antofalla terranes (to the northwest). Locally overlying these basement terranes is the Cenozoic magmatic domain, which is best developed in the N–S-trending volcanic arc at the western edge of the Puna (the Cordillera Occidental). In addition, four southeast-trending volcanic zones extend for several hundred kilometers across the Puna. Many important mineral deposits and areas of hydrothermal alteration are associated with these volcanic breakouts, and we have selected three such areas for more detailed study: Bajo de la Alumbrera (Argentina's largest porphyry copper deposit), Cerro Galán (the largest ignimbrite caldera in Argentina, with associated hydrothermal alteration zones), and El Queva (a historic polymetallic district located within a major volcanic range). A comparison of lineament maps generated from aeromagnetic and Landsat TM images reveals broad correlation between these different remote sensing techniques, which respectively highlight subsurface magnetic and surface geological features. In addition, the locations of magmatic and hydrothermal centers can be related to the interpreted structural framework, and are seen to occur near the intersections of major lineament zones. It is suggested that in three dimensions, such intersection zones form trans-lithospheric columns of low strength and high permeability during transpressional or transtensional tectonic strain, and may thereby serve as conduits for magma ascent to the shallow crust. Pooling of large volumes of deeply derived magma in shallow crustal magma chambers may then result in voluminous devolatilization and the formation of hydrothermal mineral deposits. It is important to note that in this model, structural intersections serve as facilitators for magma ascent and volatile exsolution, but do not in themselves cause this process—other factors such as magma supply rate and tectonic stress are essential primary ingredients, and local magmatic and volcanic processes affect the ultimate potential for ore formation. Nevertheless, we suggest that lineament analysis provides a valuable framework for guiding the early stages of mineral exploration; other regional and local geological considerations must then be applied to identify priority targets within this framework.