ISSN:0143-1161    

DOI:10.1080/01431169508954573

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The signal returning from the Earth's surface to the satellite is modified by the atmospheric effect, which has two components. The first one is solar radiation which, due to backscattering, is deviated in the direction of the sensor without reaching the Earth's surface. The second component is produced by the energy reflected in areas close to the pixel observed which, owing to collisions with atmospheric constituents, is deviated from its path in the sensor direction. This is called the adjacency effect and this paper presents a numerical method to estimate this effect under the assumption of a heterogeneous flat Lambertian surface. From this estimation it is possible to apply the atmospheric correction for the calculation of reflectance images based on data obtained by the optical channels of high resolution satellite systems such as Landsat-MSS, Landsat-TM and SPOT/H RV. In particular, in this paper the method is applied to Landsat-5 MSS images over urban regions. However, its application to any of the sensors mentioned is easily implemented considering the changes in spectral response and pixel size. Differences obtained in the results for reflectance at Earth's surface in winter and summer images were in the order of 10−3for bands 1 and 2, 10−2for band 3, and 10−1for band 4.

ISSN:0143-1161    

DOI:10.1080/01431169508954574

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Abstract. The Uttara Kannada coast in the State of Karnataka lying on the west coast of India, characterized by diverse terrains with widely differing structures, is an important region for many developmental activities. In order to understand its coastal landforms, and their seasonal and long term dynamics, multidate satellite data of SPOT and IRS have been studied along with the Survey of India toposheet from 1976-77 as the baseline. In the present study approximately 100 km of the coast of the Uttara Kannada district has been covered. Coastal landforms were mapped and the dynamics were assessed using satellite, collateral data and field observations. The study revealed that the coast is studded with several estuaries and creeks that support extensive mudflats, which are being used for salt production and aquaculture activities. The coast is also marked by spectacular cliffs/headlands, bays, beaches, sand dunes, spits, offshore islands, bars/shoals and river islands. The multidate data have indicated that the coast has not undergone major seasonal changes except a few modifications in the configuration and location of spits, shoals, bars mouths, etc. However, long term changes have occurred along estuarine mouths, spits, beaches and pocket beaches. Such changes are linked to the variations in the outflow from the rivers, nature, type and composition of landforms and their interaction with coastal processes operating in the study area. The study has revealed that the coast has not undergone any significant progradation or retrogration during the past two decades under study.

ISSN:0143-1161    

DOI:10.1080/01431169508954575

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The spectral response of evaporite minerals is evaluated to determine those minerals that can be identified and mapped by remote sensing. The vast majority of evaporite minerals have diagnostic spectra due to the vibration of H2O, CO3, HCO3, NH4, NO3bonds. Only the anhydrous Cl and SO4salts do not contain any diagnostic features and cannot be distinguished from each other. Many of the hydrous salts exhibit unusual spectral behaviour. Large grain size samples exhibit numerous well developed absorption features at wavelengths < 1600 nm, however, smaller grain sizes exhibit fewer less well developed features in this region and more numerous well developed features at wavelengths > 1500 nm. The spectral diversity exhibited by evaporite minerals suggests numerous applications in spectroscopy and remote sensing can be realized. These applications are investigated.

ISSN:0143-1161    

DOI:10.1080/01431169508954576

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

This paper describes two methodologies to investigate the mineral constituents of studied soil. First using a spectral analysis of states of surfaces of soils, using colour composite imagery with carefully selected channels, from a region in the south of Algeria. Second, an assessment of this study by diffractometric analysis of samples taken on a test site called Oum Deloua, near the town of Laghouat (Algeria). The obtained results, by the traced spectral signatures, allowed us to identify approximately the themes existing in the region of study. As to the diffractometric analysis, it allowed us a more accurate quantification of the elements, and thanks to the mineralogic information extracted from samples analysed helped distinguish soils very closely at first view.

ISSN:0143-1161    

DOI:10.1080/01431169508954577

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The objective of this study is to detect the current land cover classes of a representative area in the coastal agricultural land of Egypt, where changes have been observed recently due to the urban sprawl. This has been achieved after the production of different vegetation indices, and the comparison between them and their sensitivity to the environmental conditions of the area under study. This was followed by the production of profiles of different Vegetation Index (VI) images, and supervised Maximum Likelihood Classification (MLC), for the assessment of land cover classes and their cover percentage.

ISSN:0143-1161    

DOI:10.1080/01431169508954578

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Various geological and geomorphical factors play a major role at different levels in the occurrence and movement of ground water in any terrain, especially in hard rock crystalline formations. In the present study three different test sites in the form of drainage basins representing diverse geological set ups in parts of Karnataka, India have been chosen to compare and evaluate the various factors that govern the ground water occurrence and also to assess the utility of Indian Remote Sensing Satellite (IRS) sensor data in ground water mapping and condition assessment. Selected digitally enhanced products were generated and utilized for extraction of relevant details on lithology, structure and landforms by their distinct image characteristics. The integration of the details extracted from digitally enhanced products along with morphometric parameters derived from the drainage maps, helped in the assessment of ground water conditions in each basin. The comparative assessment of the ground water controlling factors of all the three drainage basins has shown that, though similar types of hydrogeomor-phic landforms have developed over these drainage basins, they vary in terms of their characteristic behaviour and spatial distribution. The results obtained encourage the use of IRS sensor data for ground water targeting especially in hard rock terrain, where it is more complex and difficult.

ISSN:0143-1161    

DOI:10.1080/01431169508954579

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Land-cover data are used for the enforcement of quota restrictions, yield estimations and agricultural statistics. With the launch of the European Remote sensing Satellite (ERS-1) the first long-term spaceborne synthetic aperture radar (SAR) has become available for the mapping of land-cover. This paper assesses the capability of ERS-1 SAR precision data to (i) discriminate between the crop types for land-cover inventory purposes at (ii) the earliest stage in the growing season, using field-based classification. The objectives were tested for an agricultural region in The Netherlands where 12 crop types are found. Fourteen ERS-1 SAR images were available for this area, covering the 1992 growing season between May and November. The field-based classification yielded an overall classification accuracy of 80 per cent with the optimal data set. The stage at which the crop types could be assessed is crop dependent. Most crop types could not be distinguished before the month of August.

ISSN:0143-1161    

DOI:10.1080/01431169508954580

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The potential of synthetic aperture radar (SAR) in monitoring soil and vegetation parameters is being evaluated in extensive investigations, worldwide. A significant experiment on this subject, the Multi-sensor Airborne Campaign (MAC 91), was carried out in the summer of 1991 on several sites in Europe, based on the NASA/JPL polarimetric synthetic aperture radar (AIR-SAR). The site of Montespertoli (Italy) was imaged three times during this campaign at P-, L-, and C-band and at different incidence angles between 20° and 50°. Calibrated full polarimetric data collected over the agricultural area of this site have been analysed and a critical analysis of the information contained in linear and circular co-polar and cross-polar data has also been carried out. Here a guideline for the formulation of crop discrimination algorithms is suggested. It has been found that P-band data are rather effective only in discriminating broad classes of agricultural landscape, while finer detail can be obtained by integrating data at L- and C-bands. Indeed at L-band well developed ‘broad leaf’ crops can be separated from the others, whereas at C-band discrimination seems feasible in the case of moderate growth as well. Finally the sensitivity of backscattering coefficient to soil moiture and vegetation biomass is discussed.

ISSN:0143-1161    

DOI:10.1080/01431169508954581

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

This paper presents results from a study on scanSAR processing and simulation. ERS-1 raw data in both normal mode and roll tilt mode are used for Doppler centroid estimation, processing and simulation. Azimuth gain variations and azimuth ambiguity ratios are evaluated for different scanning strategies and as a function of Doppler centroid errors. A scanning strategy with two scan cycles in each imaging cycle has been selected and a processing scheme with three range looks and two azimuth looks has been implemented. SPECAN is considered very favourable for azimuth processing because or its efficiency. The degradation in image quality is investigated by imposing individual (differential) beam pointing errors on real ERS-1 data. It is demonstrated in this work that the individual azimuth beam pointing errors should be less than 0004° to avoid visible degradations in homogeneous regions in the scanSAR image. Using many bursts and all subswaths for Doppler centroid estimation, it is assumed that Doppler centroid estimates will be so accurate that no image degradation is visible when azimuth intensity compensation is performed.

ISSN:0143-1161    

DOI:10.1080/01431169508954582

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor