ISSN:0143-1161    

DOI:10.1080/01431169208904245

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The International Satellite Cloud Climatology Program (ISCCP) C1 analysis of cloud amount has been compared to an analysis utilizing high resolution AVHRR imagery for twelve days in July 1983 over part of the eastern Atlantic, Western Europe and North Africa. The AVHRR analysis relies upon five individual tests requiring four spectral channels at the full 1·1 km resolution. The mean C1 cloudiness was found to be about 6 per cent greater than that of the AVHRR. However, the spatial and temporal variations in the AVHRR were found to be well simulated by the C1 analyses. Much of the difference in the means may be explained by the fact that the AVHRR cloud fractions were weighted by the fraction of partially filled sky, whereas the C1 values were not.

ISSN:0143-1161    

DOI:10.1080/01431169208904246

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The Multispectral Colour-Composite technique consists in superimposing three eight-bit images, each one resulting from a combination of channels and having a different colour (blue, green or red). It has been widely used for many years with Landsat data. The result is a coloured image where each surface type (i.e. the different clouds, the oceans, the continents, the snow) is characterized by its colour, its intensity and its texture. This technique enables a fast use of all the available channels, and avoids the visual analysis of two black and white images.

ISSN:0143-1161    

DOI:10.1080/01431169208904247

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Multispectral SPOT imagery is used to map percentage vegetation cover in the Mackenzie Basin of the South Island, New Zealand. Twenty ground measurements of quadrats 60 by 60 m2relate percentage vegetation cover to normalized vegetation index. The non-linear calibration curve is

ISSN:0143-1161    

DOI:10.1080/01431169208904248

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Ground-based solarimetric measurements on Grain Amaranthus(A. cruentus, L) were made at Akure, Nigeria Latitude 7°N; Longitude 5° E), over a growing season. The solarimeters were fitted with gelatin optical filters (Kodak No. 88A) for measurement in the infrared portion of the solar spectrum. Profile measurements within the canopy were also made at full canopy cover. Simulta neous measurements of the leaf area index (LAI), dry matter production (DM), and photosynthate partitioning (PP) were also made. Results show an increase of infrared reflectance from 0.11 to 0.35 at full canopy cover after which it starts a downward trend. The relations between normalized difference vegetation index (NDVI) and LAI and DM were cubic. It was also observed that the normalised difference was also sensitive to the phenological stage of the crop in that it shows a lower rate of increase when the partitioning of the photosynthates began. Transmitted infrared (IR) radiation within the canopy was observed to increase with depth.

ISSN:0143-1161    

DOI:10.1080/01431169208904249

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

This study was aimed at assessing the scope of Landsat Thematic Mapper (TM) data for vegetation classification and mapping needs in a tropical region of south-west India. Outputs generated through common digital enhancement/classification techniques were compared with the vegetation map prepared from visual interpretation of black and white panchromatic aerial photographs with a scale of 1:15000 (approximately), in terms of extractable thematic information and cost/time incurred. It has been shown that digital processing of TM data is capable of satisfying the classification and mapping needs in the country with a reasonable degree of precision (85 per cent), in much less cost and time when compared with the aerial photographs. Supervised classification using raw data was found to be more effective in discriminating vegetation types than enhancements like band ratioing and principal component analysis. It was possible to classify forest vegetation with respect to variability in bioclimatic and structural attributes by classification of digital data. In view of varied vegetation classification and mapping needs in India, it is suggested that as detailed a land cover classification as possible should be attempted initially. Subsequently, the detailed classification output, which is often difficult to read or understand, may be converted to user-specific simplified outputs by appropriate aggregation of classes.

ISSN:0143-1161    

DOI:10.1080/01431169208904250

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

A methodology for purification of training samples for the pixel-wise Maximum Likelihood Classification is proposed. In this method, pixels which show comparatively high local spectral variability as well as spectrally separable classes are removed from the preliminary designated training samples. An example using agricultural Thematic Mapper data shows that separability can be improved 3-78 times in terms of divergence between a specific class pair; goodness of fit to Gaussian can be improved 014 times in terms of chi-square; II’9 per cent improvement of the weighted mean percentage classification accuracy can be achieved; and, most importantly, a 20-6 per cent improvement of probability of correct classification can be achieved for a specific class.

ISSN:0143-1161    

DOI:10.1080/01431169208904251

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

A quantitative approach was pursued for identifying the most appropriate three-band combination of Landsat Thematic Mapper (TM) reflective bands data for delineating salt-affected soils of the Indo-Gangetic alluvial plain. The standard deviation and correlation coefficients values of the TM data were used for computing a statistical parameter called the 'Optimum Index Factor’ (OIF) that is indicative of the information (variance) content of the data. Amongst all the 20 three-band combinations considered, the band combination 1, 3 and 5 was found to be the best in terms of information content. The normally used band combination 2, 3 and 4 ranked relatively very low. The validation of this conclusion with the accuracy estimates of the delineation of salt-affected soils using the same data revealed a mixed relation between the ranking obtained from the OIF values and the accuracy estimates, thereby pointing towards further investigation in other areas with similar terrain conditions.

ISSN:0143-1161    

DOI:10.1080/01431169208904252

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The use of the geostationary meteorological satellite Meteosat for the estimation of rain is well known. We have used the two thermal infrared channels of the polar orbiting satellite NOAA-9/AVHR.R to obtain relations between surface temperatures measured by the satellite and rainfall measured on the ground in Senegal for the rainfall season 1987. The two channels were combined using the split window technique with the coefficients of Lagouarde. The results give high linear correlation coefficients and show that the average surface temperatures could be used as good indicators of rainfall for the same period.

ISSN:0143-1161    

DOI:10.1080/01431169208904253

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The existence of the relation between satellite-derived vegetation index and atmospheric carbon dioxide, CO2, was first shown by Tuckeret al.who used raw global vegetation index (GVI) data. In this paper, a first order atmospheric correction is applied to the GVI data. Then the northern hemispheric CO2concentration cycle is compared with the GVI dynamics over the United States of America and the United Kingdom. The results show that the GVI is a measure of the degree of photosynthetic activity in the terrestrial vegetation as was shown by Tuckeret al.In order to see the phase lag the results are presented as a function of time. When southern hemispheric CO2concentration cycle is compared with the GVI dynamics over Australia and South America (south of the equator) then it was difficult to arrive at the above conclusions. This drawback is attributed to (i) small amplitudes of CO2cycles arising due to less amount of photosynthetically active vegetation, and (ii) the occurrence of the so-calledEl Niñophenomenon on the western coast of Peru. This introduces distortions in the amplitudes of CO2cycle. Nevertheless, GVI and CO2concentration data can be used to monitor the progress that is being made in the Green Peace Movement which has been receiving some attention lately.

ISSN:0143-1161    

DOI:10.1080/01431169208904254

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor