雪盖卫星遥感信息的提取方法探讨

着重论述了从卫星遥感资料中提取雪盖信息的一些方法,结果表明,利用积雪阈值参数从ＮＯＡＡ／ＡＶＨＲＲ图象中提取雪盖信息方法和利用积雪指数（ＮＤＳＩ）从陆地卫星ＴＭ图象中提取雪盖面积的技术,以及利用ＮＯＡＡ／ＡＶＨＲＲ和ＴＭ信息复合的技术,可提高信息获取的精度,具有实用价值。     

卫星雪盖制图中的一些技术问题

介绍了几种主要卫星资料用于雪盖制图的不同时、空分辫率及应用特点，阐述了雪与云的区分技术、雪盖范围的匀绘与面积估计技术，最后指出了雪盖制图技术的一些新发展。     

Evaluating soil moisture and yield of winter wheat in the Great Plains using Landsat data

Locating areas where soil moisture is limiting to crop growth is important for estimating winter-wheat yields on a regional basis. In the 1975–76 growing season, we evaluated soil-moisture conditions and winter-wheat yields for a five-state region of the Great Plains using satellite (Landsat) estimates of leaf area index (LAI) and an evapotranspiration (ET) model described by Kanemasu et al. (1977). Because LAI was used as an input, the ET model responded to changes in crop growth. Estimated soil-water depletions were high for the Nebraska Panhandle, south-western Kansas, southeastern Colorado, and the Texas Panhandle. Estimated yields in five-state region ranged from 1.0 to 2.9 metric ton/ha.     

Meteorological satellites

Abstract

The first meteorological satellite was placed in orbit in 1960. The European programme began in earnest in 1977 with the launch of a geostationary satellite, Meteosat-1. This paper provides a brief history of the development of the Meteosat programme and describes the operational services which are provided including the range of meteorological products which are extracted routinely from the satellite data at the European Space Operations Centre (ESOC).     

Land cover change on Mt. Pinatubo,the Philippines,monitored using ASTER VNIR

Ashfall and pyroclastic flows from the large eruption of June 1991 destroyed much of the vegetation on the flanks of Mt. Pinatubo. Subsequent vegetation recovery has helped stabilize slopes and reduce debris flow hazard. In this project, visible and near-infrared (VNIR) satellite imagery from the advanced spaceborne thermal emission and reflection radiometer (ASTER) captured at a similar time of year in 2001, 2004 and 2008 were used to quantify vegetation recovery within 22 upland watersheds on the mountain, 10–16 years after the eruption took place. Differences in the normalized difference vegetation index (NDVI) derived from these images were used to measure the areal extent of losses and gains in ground cover and derive average net rates of change in ground cover. The success of this approach was dependent on post-processing ASTER imagery to correct for the effects of variation in satellite-sun geometry and vegetation reflectance and to calibrate and adjust the derived NDVI images for the influence of different atmospheric conditions at the time of image capture. All watersheds showed a variable pattern of losses and gains in vegetation and ground cover. Losses were related to shifting cultivation practices and gully and channel migration, and these amounted to 1–12% of watershed areas. Gains were related to revegetation of pyroclastic flows, recent channel terraces, abandoned gardens and areas of burnt vegetation, and these amounted to 3–45% of watershed areas. Consistent overall net gains in ground cover were observed in all watersheds, with the average NDVI increasing by up to 0.074 over each consecutive 3-year period. The rates of change in NDVI were used to derive a vegetation recovery curve from bare ground. The result showed that it will take approximately 50 years for hillslopes to regain a dense vegetative cover in this climate. This supports published findings which indicate rapid recovery of vegetation in tropical environments following such large volcanic eruptions. Results additionally showed that the trajectory of change and the speed of recovery were influenced by terrain type, geology, watershed morphology and the activity of erosion and depositional processes. Prior to 2001, revegetation had been fastest on mountain slopes that helped protect vegetation from the effects of eruption. Gains in ground cover are now greatest in areas that were most impacted by the eruption.     

小型卫星电视地面无线转播系统

目前,农村和山区卫星电视的接收大多采用小功率无线转播。本文分析了无线转播方案、卫星接收天线和转播发射天线的选择以及天线的架设、站址的确定等,并给出了我国部分城市接收中星五号、亚洲一号、东方红二号甲卫星电视时,天线的方位角和仰角,具有一定的参考价值。     

Remote sensing estimates of glacier mass balances in the Himachal Pradesh (Western Himalaya, India)

Although they correspond to an important fraction of the total area of mountain glaciers (33,000 km² out of 546,000 km²), Himalayan glaciers and their mass balance are poorly sampled. For example, between 1977 and 1999, the average area surveyed each year on the field was 6.8 km² only. No direct mass balance measurement is available after 1999. To contribute to fill this gap, we use remote sensing data to monitor glacier elevation changes and mass balances in the Spiti/Lahaul region (32.2°N, 77.6°E, Himachal Pradesh, Western Himalaya, India). Our measurements are obtained by comparing a 2004 digital elevation model (DEM) to the 2000 SRTM (Shuttle Radar Topographic Mission) topography.The 2004 DEM is derived from two SPOT5 satellite optical images without any ground control points. This is achieved thanks to the good on-board geolocation of SPOT5 scenes and using SRTM elevations as a reference on the ice free zones. Before comparison on glaciers, the two DEMs are analyzed on the stable areas surrounding the glaciers where no elevation change is expected. Two different biases are detected. A long wavelength bias affects the SPOT5 DEM and is correlated to an anomaly in the roll of the SPOT5 satellite. A bias is also observed as a function of altitude and is attributed to the SRTM dataset. Both biases are modeled and removed to permit unbiased comparison of the two DEM on the 915 km² ice-covered area digitized from an ASTER image.On most glaciers, a clear thinning is measured at low elevations, even on debris-covered tongues. Between 1999 and 2004, we obtain an overall specific mass balance of − 0.7 to − 0.85 m/a (water equivalent) depending on the density we use for the lost (or gained) material in the accumulation zone. This rate of ice loss is twice higher than the long-term (1977 to 1999) mass balance record for Himalaya indicating an increase in the pace of glacier wastage. To assess whether these ice losses are size-dependant, all glaciers were classified into three samples according to their areal extent. All three samples show ice loss, the loss being higher for glaciers larger than 30 km². In the case of the benchmark Chhota Shigri glacier, a good agreement is found between our satellite observations and the mass balances measured on the field during hydrological years 2002-2003 and 2003-2004. Future studies using a similar methodology could determine whether similar ice losses have occurred in other parts of the Himalaya and may allow evaluation of the contribution of this mountain range to ongoing sea level rise.     

卫星雪盖监测与玛纳斯河融雪径流模拟

根据国家“九五”重点科技攻关项目“冰雪水资源和出山口径流量变化及趋势预测研究”专题(96-912-01-02)的部分研究内容,运用改进后的融雪径流模型(SRM),通过天山雪盖的卫星遥感监测和流域模型参数的研究,实现了对玛纳斯河肯斯瓦特水文站春季逐日流量的数值模拟,结果表明,模拟的确定系数可达0.89,模拟积差为5.1,满足应用精度,可进一步推广应用。     

High‐resolution spatial analysis of mountain landscapes using a low‐altitude remote sensing approach

Mountain landscapes are characterized by great spatial diversity. One basic problem is that there are few high‐resolution data for secluded mountain areas. We present a new approach towards topographic mapping and vegetation monitoring: low‐altitude remote sensing using Kite Aerial Photography (KAP). The study was conducted in the Norwegian mountains above the treeline. We assessed this approach under specific alpine circumstances. Following the collection of data, we derived a digital elevation model (DEM) from two overlapping images. The model was evaluated by the statistical correlation of 265 random field points and extracted heights from (i) linear contour line interpolation of a topographic map of scale 1 : 50 000, (ii) photogrammetric analysis of kite aerial photographs, and (iii) kriging interpolation of approximately 1000 measured field points. Finally, the vegetation was classified, using both supervised and unsupervised methods. The accuracy of the classification results was evaluated by comparing 265 random points, derived from terrestrial mappings, to classified vegetation types by an error matrix. The generation of derived data compared well with data obtained from high‐resolution field surveys and was better than data derived from public‐domain government cartography and moderate‐scale satellite remote sensing data. Our results demonstrate the economic and logistic advantages of this new KAP‐based methodology. The flexibility and outstanding high resolution of our new low‐altitude remote sensing approach proved to be particularly suitable for closing the gap between terrestrial investigations and high‐altitude remote sensing. Hence, our KAP approach addresses the challenge of multiscale research in mountain landscapes.     

高速可编程遥感卫星数据模拟源的设计与实现

本文以高性能可编程逻辑器件,高精度、低抖动、低畸变可编程时钟芯片为核心器件,采用PCI总线技术,设计了高速可编程遥感卫星数据模拟源,在使用windows2000的高性能服务器上,实现了1MHz￣400MHz,步进为1MHz,逐步可编程模拟卫星信号输出,有效的解决了遥感卫星地面记录系统维护和开发的数据源问题。     

Cloud classification from visible and infrared SMS-1 data

The success of a statistical classification-design sample model in discriminating cloud-type samples of visible and infrared meteorological satellite data depends on the selection of the design parameters for the system and the ability of the labelled design samples to characterize and discriminate class patterns within the given geographical region. In a companion study by Parikh (1977), pattern recognition design parameters were examined for a four-class problem and a three-class problem for NOAA-1 cloud data. The purpose of this study was to evaluate pattern recognition systems designed in the previous study on SMS-1 design and test sets. Experiments were conducted for both a four-class problem (separation of “low”, “mix”, “cirrus”, and “cumulonimbus” samples) and a three-class problem (separation of “low”, “cirrus”, and “cumulonimbus” samples). For the four-class problem, decreases in classification accuracy ranging from 4% to 11% occurred when the pattern recognition systems were designed and tested on two different data sets selected from the same satellite orbit. A similar decrease was not observed for the well-defined three-class problem.     

Using satellite remote sensing for DEM extraction in complex mountainous terrain: Landscape analysis of the Makalu Barun National Park of eastern Nepal

The design and management of national parks and other protected areas requires a broad base of physiographic and geo-ecological information about the landscape. This paper evaluates the effectiveness of satellite remote sensing for photogrammetric stereo-mapping and digital elevation model (DEM) extraction within remote mountainous terrain. As a case study, a landscape analysis of the Makalu Barun National Park and Conservation Area of east Nepal (27.5° N, 87.0° E) was examined. The study area is a highly complex and rugged mountain landscape, with extreme topographic relief and an elevation gradient spanning more than 8300 m. A DEM extracted from stereo SPOT imagery resulted in a median disagreement of 58 m when compared to a DEM generated from a conventionally digitized GIS dataset of topographic contours (scale=1:250 000). Visual comparison of the two DEMs showed substantial agreement at the landscape scale, while larger scale comparison of 100 m contours revealed some localized differences. The SPOT extracted DEM provided equal or better basis for orthorectification of satellite imagery when compared to the conventional DEM. Derivative landscape analysis outputs, such as hydrological modelling, drainage networks and watershed boundaries, compared well with results based upon the conventional dataset. Intermediate map products useful for field research and mapping included production of an orthorectified satellite base-map image. Additionally, a fused multisensor high resolution image of the study area, combining Landsat Thematic Mapper (TM) and SPOT imagery at 10 m resolution, was orthorectified to produce a false-colour satellite image map highlighting the spectral discrimination between land cover classes.     

DEM generation using ASAR (ENVISAT) for addressing the lack of freshwater ecosystems management,Santa Cruz Island,Galapagos

Low relief oceanic islands often suffer from scarcity of freshwater resources. Remote sensing has proved to be an effective tool to generate valuable data for hydrological analysis and has improved the management of ecosystems and water. However, remotely sensed data are often tested over areas with existing validation databases and not always where the need is greatest. In this paper we address the need for topographical data to understand the hydrological system of Santa Cruz Island (Galapagos archipelago) so that management of freshwater ecosystems and resources can take place. No high resolution, high accuracy topographical data exist for Santa Cruz Island, and its growing population has created an urgent need for water resource management and protection of unique and pristine ecosystems.Inaccessible National Park land covers more than 97% of Galapagos territory, which makes the use of remote sensing methods indispensable. SRTM data was insufficient in terms of grid size (90 m) to carry out the needed data analysis. We used ASAR data (ENVISAT) in VV polarization image mode for Digital Elevation Model (DEM) generation, in order to extract drainage network, watersheds, and flow characteristics from a morpho-structural analysis.Results show the high potential of these data for both interferometric and radargrammetric generation methods. Although interferometry suffered from low coherence over highly vegetated areas, it showed high precision over the rest of the island. Radargrammetry gave consistent results over the entire island, and details were enhanced by integrating the 90 m SRTM data as an external DEM. Accuracy of the SRTM and the combined radargrammetric/SRTM DEM was similar, with the radargrammetric having a finer pixel-based resolution (20 m).Validation of the extracted drainage networks and watersheds was carried out using ground-based field observations and comparison to mapped river networks visually extracted from aerial photographs and high resolution (1 m) satellite imagery available on GoogleEarth^©. For the first time, watershed characteristics and flow paths were made available for an island of the Galapagos archipelago. Furthermore, the drainage network is shown to be strongly influenced by observed and extracted structural discontinuities. Having characterized freshwater flow, water balance calculations were carried out for Pelican Bay watershed, where urban areas, agricultural land and Galapagos National Park land are concomitant.     

基于Landsat8热红外遥感数据的山地地表温度地形效应研究

地表温度是影响地表能量收支平衡的重要参量,能够综合反演地表的水热交换过程。虽然当前在基于地表温度开展全球或者区域尺度的地表能量平衡研究方面取得一系列的进展,但是面向山地区域尺度的类似研究仍然面临较大的挑战。为分析山地复杂地形对山地地表温度时空分布的影响规律,基于具有较高空间分辨率的Landsat 8热红外数据,以我国西南典型山地为研究对象,定量反演该区域的地表温度空间分布状况,结合SRTM90DEM数据,选择从海拔、坡度和坡向3个关键地形因子角度分析山地地表温度的地形效应特征。结果发现:山地地表温度随地形因子均呈现出十分显著的变化特征。总体而言,地表温度均随着海拔和坡度的升高而降低,而在坡向方面,南坡的温度相比北坡的温度要高。在地形效应分析的基础上,通过开展1km空间尺度地形和地表温度的空间统计分析发现,山地1km尺度下地表温度存在较大的空间异质性,且其影响不可忽略。研究结果表明:开展山地地表水热过程遥感动态监测需高空间分辨率地表温度作为数据支持,以准确描述山地地形因素对地表能量交换过程的影响。     

Satellite estimation of tropical secondary forest above-ground biomass: Data from Brazil and Bolivia

This paper reports on a test of the ability to estimate above-ground biomass of tropical secondary forest from canopy spectral reflectance using satellite optical data. Landsat Thematic Mapper data were acquired concurrent with field surveys conducted in secondary forest fallows near Manaus, Brazil and Santa Cruz de la Sierra, Bolivia. Measurements of age and above-ground live biomass were made in 34 regrowth stands. Satellite data were converted to surface reflectances and compared with regrowth stand age, biomass and structural variables. Among the Brazilian stands, significant relationships were observed between middle-infrared reflectance and stand age, height, volume and biomass. The canopy reflectance-biomass relationship saturated at around 15.0 kg m^-2, or over 15 years of age (r > 0.80, p < 0.01). In the Bolivian study area, no significant relationship between canopy spectral reflectance and biomass was observed. These contrasting results are probably caused by a low Sun angle during the satellite measurements from Bolivia. However, regrowth structural and general compositional differences between the two study areas could explain the lack of a significant relationship in Bolivia. The results demonstrate a current potential for biomass estimation of secondary forests with satellite optical data in some, but not all, tropical regions. A discussion of the potential for regional extrapolation of spectral relationships and future satellite imagery is included.     

Improving accuracy of long-term land-use change in coal mining areas using wavelets and Support Vector Machines

Old satellite sensors lack several quality features such as high spatial and spectral resolution. For accurate long-term change detection, improvement of the quality of old satellite images is required. In the present study, we used two wavelet-based image enhancement techniques [(discrete wavelet transform (DWT) and dual tree-complex wavelet transform (DT-CWT)] for improving the quality of Landsat 2 data of 1975 and Landsat 8 data of 2015 to study the impact of coal mining on land use change over a period of four decades. The enhanced images were subjected to land-use classification using Support Vector Machines. Land-use classification accuracy was measured using confusion matrix-based accuracy assessment. Accuracy assessment revealed that the overall classification accuracy of DWT enhanced images was 82.10% for the year 1975 and 88.46% for the year 2015. The overall classification accuracy of DT-CWT enhanced images was 85.71% for the year 1975 and 88.54% for the year 2015. The results of change detection revealed that the total areal coverage of dense vegetation increased by 65%, indicating that the rate of land degradation had slowed down due to the legislative and policy changes to promote sustainable development in coal mining after 1986.     

Updating geomorphic features of watersheds and their boundaries in hazardous areas using satellite synthetic aperture radar

Volcanic disasters can cause severe loss of human life and damage to property. The main damage is caused during an eruption and from subsequent erosion of deposited materials. Heavy rainfall in volcanic areas erodes volcanic deposits, mainly pyroclastic flows and ash fall deposits, which flow as lahar to the foothill of the mountain and cause drastic damage to economically important areas. This post-eruption disaster becomes complex due to the occurrence of stream captures and watershed breakouts that lead to devastating lahars. Continuous monitoring of such geomorphic and hydrologic changes is necessary to cope with changing hazard conditions. Therefore it is important to update the watershed boundaries in order to study current hazard conditions and develop mitigation plans for future disasters. Changes of geomorphic and watershed boundary have occurred in the Mayon Volcano in the Philippines mainly as a result of a major volcanic eruption of 1993, due to which mitigation structures were constructed and modified in the low lying areas. In this study interferometry was used to develop DEM from SAR data to delineate watershed boundaries. New lava flows, pyroclastic flows and lahar deposits in the watersheds were mapped using elevation changes, coherence and intensity derived from the SAR images. Updating geomorphic features of the watersheds and their boundaries using SAR provides a new weather independent alternative technique for monitoring the effect of volcanic activity.     

The Kamishak Gap wind as depicted in DMSP OLS and SSM/I data

Abstract

DMSP visual and infrared Operational Line Scanner (OLS) data reveal several effects of a mountain gap wind generated by wind flow through the Kamishak Gap on the west side of Cook Inlet, Alaska. The existence of the wind can be inferred through one of three separate effects apparent in the data: (1) a roughened sea effect, appearing as a dark grey shade swath within a sunglint pattern; (2) an anomalous grey shade effect induced by sea spray and aerosols, and, (3) a multiple cloud line effect originating as a result of a moisture flux from the sea to the air in a high speed, cold air, coastal outbreak. The Special Sensor Microwave Imager (SSM/I) of the DMSP satellite provides another means to detect the Kamishak Gap wind due to the sensitivity of this sensor to changes in microwave emission of the sea surface as a result of sea spray and foam in high wind speed areas and to associated changes in integrated water vapour content (oceanic total precipitable water). Developed algorithms provide a methodology to quantify from a satellite perspective some of the characterisitics of such events.     

Visualizing gridded time series data with self organizing maps: An application to multi-year snow dynamics in the Northern Hemisphere

Gridded time-series data are increasingly available for climatology research. Microwave imagery of snow water equivalent (SWE) has been accumulated at daily basis for over two decades, but complex spatial-temporal patterns in SWE dataset pose great challenges for exploration and interpretation. This paper introduces the use of several perspectives from a tri-space conceptualization of a time series of SWE grids combined with dimensionality reduction via the self-organizing map (SOM) method. While SOM has been predominantly viewed as a clustering mechanism within climatology research, we expand the visual-analytic potential of SOM for climate research with a series of conceptual, computational, and visual transformations. Specifically, we apply a medium-resolution SOM to an SWE dataset covering the Northern Hemisphere over a 20-year period, with high temporal resolution. Through clustering and visualization a number of distinct SWE patterns are identified, including mountainous, coastal, and continental regions. A subset of cells from six areas are selected for transition analysis, including mountainous (Sierra Nevada, Western Himalaya, Eastern Himalaya) and continental (central Siberia, western Russia and Midwest United States) regions. By combining with trajectory analysis, this SOM documents notable transitions in seasonal SWE accumulation and melt patterns in mountain ranges, suggesting that SWE in some geographic locations alternates between different discrete annual patterns. In the Sierra Nevada, transitions to classes with high SWE are shown to be related to the Southern Oscillation Index, demonstrating that the annual patterns and transitions in SWE regime identified by the SOM correspond to synoptic climate conditions.     

Quantifying burn severity in a heterogeneous landscape with a relative version of the delta Normalized Burn Ratio (dNBR)

Multi-temporal change detection is commonly used in the detection of changes to ecosystems. Differencing single band indices derived from multispectral pre- and post-fire images is one of the most frequently used change detection algorithms. In this paper we examine a commonly used index used in mapping fire effects due to wildland fire. Subtracting a post-fire from a pre-fire image derived index produces a measure of absolute change which then can be used to estimate total carbon release, biomass loss, smoke production, etc. Measuring absolute change however, may be inappropriate when assessing ecological impacts. In a pixel with a sparse tree canopy for example, differencing a vegetation index will measure a small change due stand-replacing fire. Similarly, differencing will produce a large change value in a pixel experiencing stand-replacing fire that had a dense pre-fire tree canopy. If all stand-replacing fire is defined as severe fire, then thresholding an absolute change image derived through image differencing to produce a categorical classification of burn severity can result in misclassification of low vegetated pixels. Misclassification of low vegetated pixels also happens when classifying severity in different vegetation types within the same fire perimeter with one set of thresholds. Comparisons of classifications derived from thresholds of dNBR and relative dNBR data for individual fires may result in similar classification accuracies. However, classifications of relative dNBR data can produce higher accuracies on average for the high burn severity category than dNBR classifications derived from a universal set of thresholds applied across multiple fires. This is important when mapping historic fires where precise field based severity data may not be available to aid in classification. Implementation of a relative index will also allow a more direct comparison of severity between fires across space and time which is important for landscape level analysis. In this paper we present a relative version of dNBR based upon field data from 14 fires in the Sierra Nevada mountain range of California, USA. The methods presented may have application to other types of disturbance events.