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1.
The study presents digital preprocessing techniques, visual mapping capability of airborne X-band SAR data having diverse vegetation types in tropical wet climate. Spatial textural analysis methods have also been evaluated to enhance discriminability of the forest types and features. Attempt has been made to enhance the information by merging optical remote sensing data with microwave X-band response. Finally, the backscattering digital values have been correlated with qualitative and quantitative vegetation parameters. The Leaf Area Index has shown significant relationship with SAR image digital number value.  相似文献   

2.
An insight into the geomorphic evolution of any area can be obtained by detailed landform mapping. In the present study, an area in the Middle Ganga Plain has been selected for the study using mainly remote sensing data. Various fluvial landforms have been mapped and the changes in planform of rivers over approximately 50 years have been evaluated. Both fluvial processes and tectonic activities are considered to have collectively influenced the migration of the rivers in this region. Digital enhancements of Landsat MSS and TM data are found to be quite useful in identification and mapping of subtle fluvial palaeofeatures. The present study demonstrates the utility of remote sensing in examining the geomorphic evolution of the area.  相似文献   

3.
Indian Remote Sensing Satellite-1A (IRS-1A) LISS-II data of 24th Nov., 1988 was analysed digitally to differentiate three density classes viz. dense/closed forest, open forest and degraded forest within each vegetation type in the district, Jalpaiguri, West Bengal. Stratification approach was used to classify separately forest cover into pure sal forests, mixed forests, riverine forests along with man-made sal/teak plantations. In this approach the forested and non-forested areas were classified separately through supervised classification techniques using maximum likelihood algorithm using VAX 11/780 based VIPS-32 Image Processing software. Later the two classified outputs were composited to provide entire area of the district. The forest cover of the district was 1420.89 sq. km, (22.82 percent). Other broad landuse/landcover dominant in the district include agricultural areas.(45.20 percent) and tea gardens (10.49 percent). The accuracy of the classified output was estimated to be 90 percent for forested areas and 85 percent in case of other landuse/landcover classes.  相似文献   

4.
Ground based remote sensing experiments using multispectral radiometer were condueted during December 1992 to March 1993, at horticultural field of Mahatma Phule Krishi Vidyapeeth, located in Pune, over banana, grapes, brinjal and tomato crops for studying the spectral response at different growth stages and vigour. The spectral characteristics and the various vegetative indices of diseased and healthy plants are discussed in this paper. Besides its significance in ground based remote sensing, these studies may be helpful for decision making in the area of condition assessment of crops through satellite remote sensing, as the spectral bands of the radiometer used in this experiment are similar to those of IRS and Landsat satellites. Moreover, the growth profiles of brinjal and banana crops can be useful in the area of crop and vegetable discrimination.  相似文献   

5.
Digital analysis of IRS 1A LISS-II (23-03-1991) data was used to delineate social forestry plantations in Matar taluka of Kheda district, Gujarat. VAX 11/780 image processing system was used to categorise the various plantations using supervised maximum likelihood classification. The classified output yielded three categories of plantations viz.,Eucalyptus spp.,Acacia spp., and mixed spp. The statistics for all the categories were also generated.  相似文献   

6.
Synthetic Aperture Radar (SAR) data from the European Remote Sensing Satellite (ERS-1) acquired in July, October and November, 1992 covering the kharif season of the region were used separately and in combination to identify the major crops and for estimation of their acreage before harvest Separability indices were calculated for major cover types and it was found that single-date SAR data cannot be used for accurate identification of various crops. Multi-temporal colour composite facilitated better identification of crop types. Comparison of area estimates made with ERS-1 SAR and IRS-1B LISS II data showed that the commonly used digital data analysis techniques (per pixel classifiers) are not adequate for accurate estimation of crop acreage using SAR data.  相似文献   

7.
The spectral reflectance characteristics of different types of natural and anthropogenic salt-affected soils have been studied under field conditions. The spectral reflectance value for non-saline and all types of salt-affected soils was maximum in near infra red region (800–1000 nm). The natural salt-affected soils having surface salt encrustation showed highest reflectance value followed by the sodic soils (formed due to high residual sodium carbonate water irrigation) natural saline soils and saline soils due to saline water irrigation. Soil texture, pH, CaC03 and organic matter together accounted for 29.6% variation in the maximum reflectance percentage value out of which only pH accounted for more than half (14.2% variation).  相似文献   

8.
Conventional techniques of monitoring both long-term and short-term changes in river morphology is time consuming and expensive. Remote sensing with its synoptic and temporal capability is an effective tool to study river metamorphosis. The present study is carried out in lower Ganga basin where Hooghly river is an important river contributing sediment to this vast fertile plain. A time series planform analysis is carried out between 1971 to 1991 period. Thematic maps generated from Landsat MSS and IRS-IA LLSS-I satellite data for 1986 and 1991 period respectively is compared with 1971 topographic maps. The migratory character of paleocourse of Hooghly river is deciphered through the paleochannels, oxbow takes and meander scars deciphered from satellite imagery. The shortterm river metamorphosis like cut-offs, bar migration and point bar accretion morphology are mapped and compared with 1971 topographic maps. The critical zone with respect to cut-offs and future channel migration are identified for river stabilization work.  相似文献   

9.
In order to understand the dynamic aspects of suspended sediments in an inland water body, Tungabhadra reservoir on the Tungabhadra river in the Krishna basin was studied. The study has been carried out using Landsat MSS and IRS-1 A LISS-II images. Visual interpretation techniques have been used to obtain information on the location and extent of sediment distribution pattern in the water-spread area of the reservoir. It has been possible to monitor the seasonal fluctuations in the reservoir water-spread; measure corresponding fluctuation in the volume of water in the reservoir, and study seasonal changes in the suspended sediment distribution pattern in the reservoir. An attempt has also been made to prepare area capacity curve for the reservoir. Semi-quantitative assessment of sediment deposits between reservoir levels were made considering water spread area from the satellite images (May 1986, April 1987, Jan. 1988, Jan. 1989 and March 1989) and sedimentation survey report of KERS 1985, (Karnataka Engineering Research Station). The results indicated that the high Concentration of sediments is at the western confluence of the Tungabhadra river. On the basis of tonal variation as observed, the reservoir could be divided into four major zones, viz., very high and high at the river confluence, moderate at the periphery and low at the dam site.  相似文献   

10.
Remote sensing techniques have been applied to classify tour density classes within each of the forest type along with other major landuse/landcover classes in the East district, Sikkim using IRS-1A LISS II satellite data pertaining to the period of November, 1988. The shadow problem in rugged terrain and difficulty in acquiring cloud free data for different seasons pose problems to achieve considerable mapping accuracy. In the present study, the forests of the district were delineated through supervised classification techniques using maximum likelihood algorithm into five forest types as sal forests, subtropical broad-leaved forests, Himalayan wet temperate forests, Rhododendron forests and alpine forests. The alpine forests were further stratified into two categories as moist alpine scrub and dry alpine scrub. The statistical data obtained from the present study shows that 55.47 percent of the total geographical area of the East district was under forest cover. An overall accuracy of more than 85 percent in correctly delineating forest classes was achieved.  相似文献   

11.
本研究着眼于广东省典型特色农作物的波谱，建立了波谱数据库，该库分为知识库、遥感实测波谱库、模型库、波谱分析和 荔枝园示范5大部分。 在波谱分析模块设计上提供了波谱数据查询、分析等功能，通过对荔枝园种植面积应用示范，给用户提供了极 大方便。  相似文献   

12.
植被物候遥感监测研究进展   总被引：11，自引：0，他引：11  
植被物候是研究植被与气候、环境变化间关系的重要参量。本文针对目前常用的阈值法、拟合法和延迟滑动平均法等植被物候遥感监测方法进行比较分析;介绍了传感器网络法、物候模型法等物候遥感监测验证方法;从遥感监测方法和数据源两方面分析物候遥感监测的误差来源;针对目前研究中存在的问题,讨论了遥感物候的主要研究方向:从机理层面,应创新植被物候遥感监测方法;建立标准化地面验证数据源;利用多源遥感数据,组成高时间分辨率的原始遥感数据源,提高植被物候遥感监测的时间分辨率和测算精度。  相似文献   

13.
从高光谱遥感影像提取植被信息   总被引：2，自引：0，他引：2  
遥感可以快速有效地监测大面积植被的种类、特性、长势等各类信息。高光谱遥感数据因其特有的高光谱分辨率特性使其在植被生态环境领域具有极大的应用潜力。植被信息作为生态环境评价的重要参数对区域生态环境的监测和建设具有重要的意义。本文基于云南省鹤庆县北衙的高光谱遥感数据用SAM方法对植被信息进行了提取,参考光谱使用ASD光谱辐射仪采集的植被光谱曲线。文中对高光谱遥感影像的辐射定标和大气校正进行了研究,针对影响光谱辐射仪采集的主要因素采取了相应的措施,并对光谱曲线分类及参考光谱曲线的选取进行了研究。将选取出的参考光谱曲线与大气校正后的遥感影像进行SAM匹配提取出植被信息,经过与实地调查资料比较并计算总体精度和kappa系数,计算结果达到预期精度。最后将分类结果转换为矢量图,经过投影转换为大地坐标后制作出北衙植被分布图。  相似文献   

14.
微波植被指数在干旱监测中的应用   总被引：3，自引：0，他引：3  
在植被覆盖区域,归一化植被指数(NDVI)被广泛地应用于干旱遥感监测。和基于光学遥感的植被指数相比,Shi等提出的微波植被指数MVI(Microwave Vegetation Index)被证实能够反映更多的植被生长信息。本文以MVI为基础,利用MVI代替目前比较成熟的温度植被指数TVDI(Temperature Vegetation Index)中的NDVI,构建温度微波植被干旱指数TMVDI(Temperature Microwave Vegetation Index),发展了一种新的干旱监测方法。本文以2006年夏季四川省发生的百年难遇的干旱为研究对象,将基于TMVDI与TVDI的干旱监测结果进行了对比分析。最后,为评估监测结果的准确性,将遥感监测的结果与基于气象站点降雨观测数据构建的标准降雨指数SPI(Standardized Precipitation Index)的计算结果进行了对比分析。结果表明,利用低频降轨微波辐射计数据计算的T MVDI最适合于进行植被覆盖区域的干旱监测。  相似文献   

15.
基于东亚飞蝗生育周期的遥感蝗灾监测新模式   总被引：6，自引：1，他引：6  
当前 ,国际遥感蝗灾监测的技术路线一般是爆发蝗灾后受损面积、程度的监测与评价 ,研究灾害的有效预警与预测方法 ,对防灾减灾更具有现实意义。通过连续 2 0 0 1、2 0 0 2年连续实地对渤海湾夏蝗孵化期、生长期和成虫期等 7个阶段的野外观测 ,对蝗虫生境物理和生物依赖条件样方统计、光谱测试和遥感机理实验 ,提出了“飞蝗生育周期遥感三段监测”的论点 ,根据这个论点将遥感监测设计为 3个阶段 :(1 )孵化期水热条件遥感反演 ;(2 )生长期食量猛增遥感监测芦苇叶面积指数和植被盖度变化 ;(3)成虫期寻找新食源对芦苇盖度 (温度 )和地表水条件 ,进而对聚集条件和迁移方向的分析指导灭蝗。有效发挥了遥感连续动态观测的技术特点 ,为建立环渤海湾东亚飞蝗遥感监测体系提供了基本技术路线 ,介绍的思路与方法也可以对森林病虫害等大规模突发病虫灾害起到借鉴作用  相似文献   

16.
The spread of invasive Australia native Acacia tree species threatens biodiversity and adversely affecting on vegetative structure and function, including plant community composition, quantity and quality worldwide. It is essential to provide researchers and land managers for biological invasion science and management with accurate information of the distribution of invasive alien species and their dynamics. Remotely sensed data that reveal spatial distribution of the earth’s surface features/objects provide great potential for this purpose. Consistent satellite monitoring of alien invasive plants is often difficult because of lack of sufficient spectral contrast between them and co-occurring plants species. Time series analysis of spectral properties of the species can reveal timing of their variations among adjacent species. This information can improve accuracy of invasive species discrimination and mapping using remote sensing data at large scale. We sought to identify and better understand the optimal time window and key spectral features sufficient to detect invasive Acacia trees in heterogeneous forested landscape in South Africa. We explored one-year (January to December 2018) time series spectral bands and vegetation indices derived from optical Copernicus Sentinel-2 data. The attributes correspond to geographical information of invasive Acacia and native species recorded during a field survey undertaken from 21 February to 25 February 2018 over Kwa-Zulu Natal grasslands landscape, in South Africa. The results showed comparable separability prospects between times series of spectral bands and that of vegetation indices.Substantial differences between Acacia species and native species were observed from spectral indices and spectral bands which are sensitive to Leaf Area Index, canopy chlorophyll and nitrogen concentrations. The results further revealed spectral differences between Acacia species and co-occurring native vegetation in April (senescence for deciduous plants), June-July (dry season), September (peak flowering period of Acacia spp) and December (leaf green-up) with vegetation indices (overall accuracy > 80 %). While spectral bands showed the beginning of the growing season (November–January) and peak vegetation productivity (February-March) as the optimal seasons or dates for image acquisition for discriminating Acacias from its co-occurring native species (overall accuracy > 80 %). In general, the use of Sentinel-2 time series spectral bands and vegetation indices has increased our understanding of Australian Acacias spectral dynamics, and proved that the sentinel-2 data is useful for characterization and monitoring Acacias over a large scale. Our results and approach could assist in deriving detailed geographic information of the species and assessment of a spread invasive plant species and severity of invasion.  相似文献   

17.
高光谱吸收特征参数反演草地光合有效辐射吸收率   总被引：1，自引：0，他引：1  
在植被光合有效辐射吸收率(FAPAR)遥感估算中被广泛采用的植被指数法,其估算精度往往受到"红波段吸收峰"峰值点光谱反射率易饱和特征的影响。考虑到高光谱吸收特征参数能较好地诠释地物光谱吸收特征的细节信息,基于微分法与包络线去除法研发"高光谱曲线特征吸收峰自动识别法"识别对FAPAR敏感的特征吸收峰,再结合连续统去除法以及光谱吸收指数(SAI)提取FAPAR的高光谱吸收特征参数,构建估算天然草地冠层水平FAPAR的高光谱吸收特征参数模型。结果表明:(1)天然草地冠层FAPAR与高光谱吸收特征参数具有很好的相关性,其中,"红波段吸收峰"SAI对FAPAR变化最为敏感,在植被覆盖度较高时,其饱和性相比"红波段吸收峰"峰值点反射率与归一化植被(NDVI)值有较大的提升。(2)以"红波段吸收峰"SAI为变量的对数方程为FAPAR的最佳估算模型,在植被覆盖度处于中与高时,其FAPAR预测精度比NDVI模型有不同程度的提高。研究采用的高光谱吸收特征参数一定程度上弥补了部分植被指数因饱和问题在估算FAPAR时的不足,可作为植被FAPAR反演的新参数,适用于中、高覆盖度的天然草地FAPAR监测。  相似文献   

18.
This work is an investigation of three methods for regional geoid computation: Stokes’s formula, least-squares collocation (LSC), and spherical radial base functions (RBFs) using the spline kernel (SK). It is a first attempt to compare the three methods theoretically and numerically in a unified framework. While Stokes integration and LSC may be regarded as classic methods for regional geoid computation, RBFs may still be regarded as a modern approach. All methods are theoretically equal when applied globally, and we therefore expect them to give comparable results in regional applications. However, it has been shown by de Min (Bull Géod 69:223–232, 1995. doi: 10.1007/BF00806734) that the equivalence of Stokes’s formula and LSC does not hold in regional applications without modifying the cross-covariance function. In order to make all methods comparable in regional applications, the corresponding modification has been introduced also in the SK. Ultimately, we present numerical examples comparing Stokes’s formula, LSC, and SKs in a closed-loop environment using synthetic noise-free data, to verify their equivalence. All agree on the millimeter level.  相似文献   

19.
Remote sensing has proved to be a powerful resource in geology capable of delineating target exploration areas for several deposit types. Only recently, these methodologies have been used for the detection of lithium (Li)-bearing pegmatites. This happened because of the growing importance and demand of Li for the construction of Li-ion batteries for electric cars. The objective of this study was to develop innovative and effective remote sensing methodologies capable of identifying Li-pegmatites through alteration mapping and through the direct identification of Li-bearing minerals. For that, cloud free Landsat-5, Landsat-8, Sentinel-2 and ASTER images with low vegetation coverage were used. The image processing methods included: RGB (red, green, blue) combinations, band ratios and selective principal component analysis (PCA). The study area of this work is the Fregeneda (Salamanca, Spain)-Almendra (Vila Nova de Foz Côa, Portugal) region, where different known types of Li-pegmatites have been mapped. This study proposes new RGB combinations, band ratios and subsets for selective PCA capable of differentiating the spectral signatures of the Li-bearing pegmatites from the spectral signatures of the host rocks. The potential and limitations of the methodologies proposed are discussed, but overall there is a great potential for the identification of Li-bearing pegmatites using remote sensing. The results obtained could be improved using sensors with a better spatial and spectral resolution.  相似文献   

20.
A seamless vegetation type map of India (scale 1: 50,000) prepared using medium-resolution IRS LISS-III images is presented. The map was created using an on-screen visual interpretation technique and has an accuracy of 90%, as assessed using 15,565 ground control points. India has hitherto been using potential vegetation/forest type map prepared by Champion and Seth in 1968. We characterized and mapped further the vegetation type distribution in the country in terms of occurrence and distribution, area occupancy, percentage of protected area (PA) covered by each vegetation type, range of elevation, mean annual temperature and precipitation over the past 100 years. A remote sensing-amenable hierarchical classification scheme that accommodates natural and semi-natural systems was conceptualized, and the natural vegetation was classified into forests, scrub/shrub lands and grasslands on the basis of extent of vegetation cover. We discuss the distribution and potential utility of the vegetation type map in a broad range of ecological, climatic and conservation applications from global, national and local perspectives. We used 15,565 ground control points to assess the accuracy of products available globally (i.e., GlobCover, Holdridge’s life zone map and potential natural vegetation (PNV) maps). Hence we recommend that the map prepared herein be used widely. This vegetation type map is the most comprehensive one developed for India so far. It was prepared using 23.5 m seasonal satellite remote sensing data, field samples and information relating to the biogeography, climate and soil. The digital map is now available through a web portal (http://bis.iirs.gov.in).  相似文献   

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