ISSN:0143-1161    

DOI:10.1080/01431169008955051

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

A methodology for ocean colour analysis in coastal zones through airborne sensors is introduced and applied to multispectral data gathered at different altitude over test sites in the Northern Adriatic Sea. Data obtained by the Ocean Color Radiometer (working in the same bands of the Coastal Zone Color Scanner) and the Six Channel Radiometer (working in the spectral region characterized by natural fluorescence of chlorophyll) have been corrected for atmospheric and sea-surface effects by modelling radiative processes involved in remote sensing of water colour. Water radiance spectra and chlorophyll and sediment concentrations, derived from remotely sensed data corrected for atmospheric and sea-surface effects, demonstrate the capabilities of the methodology in performing quantitative analysis of materials suspended or dissolved in sea water.

ISSN:0143-1161    

DOI:10.1080/01431169008955052

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Improved parameters for a soil-adjusted vegetation index (SAVI) are derived using SAIL model output for simulated wheat canopy reflectance. The SAVI is much less sensitive than the ratio vegetation index to changes in background caused by soil colour or surface soil moisture content. The parameters are developed to minimize variability due to soil brightness over the practical range of solar elevations, lear angle distributions (LAD) and leaf area indices (LAI). The parameters are added to the near-infrared (NIR) and red reflectances before calculating the NIR/red ratio. Three new versions of the SAVI are developed based on the theoretical consideration of the effects of wet and dry soils. All three are superior to the NIR/red ratio, the perpendicular vegetation index and a soil-adjusted vegetation index. Our simplest version requires the addition of a parameter to the red reflectance. The second and third versions require an iterative procedure to find the best parameters that are then added to the red or the NIR and red reflectances. In general, SAVI adjustment parameters required to remove soil-brightness effects decrease as factors that obscure the soil-surface increase. Low solar elevation and high LAI result in increasingly negative values for the parameters. The NIR/red ratio is the vegetation index least influenced by soil brightness at LAI greater than three. Our iterated versions have lowest overall errors but are occasionally subject to higher errors at the combination of low zenith angles and erectophile canopies. The SAVI based on the bare soil reflectance performs best on field data.

ISSN:0143-1161    

DOI:10.1080/01431169008955053

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

This paper reports the application of deriving evapotranspiration and thermal inertia from thermal and visible infrared Meteosat data to Sahelian wetlands: the Niger Delta in Mali and the Logone/Chari/Chad system in Chad.

ISSN:0143-1161    

DOI:10.1080/01431169008955054

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The Special Sensor Microwave/Imager (SSM/I) flying on the most recent satellite of the Defense Meteorological Satellite Program (DMSP) measures radiation from the Earth-atmosphere system within millimetre wavelengths. This radiation is strongly modified by the varying atmospheric water-vapour content. A technique to derive the water-vapour content over oceans from these measurements is developed. The sensor system is studied theoretically by calculating the radiative transfer for a non-scattering atmosphere in the appropriate spectral channels for a large set of atmospheric/oceanic situations. Subsequently, statistical retrieval coefficients are derived via a regression analysis of the synthetic measurements. Approaches using one to three spectral channels enable us to derive water vapour amounts in vertical columns with accuracies from 0.145 to 0.17g/cm2. A case study with real SSM/I data demonstrates the capability of the system to derive atmospheric water-vapour fields over the global ocean within a period of a few days. The accuracy evaluated is confirmed through globally distributed match-ups with radiosonde measurements.

ISSN:0143-1161    

DOI:10.1080/01431169008955055

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Remotely-sensed data from a series of overflights of the Clyde estuary in western Scotland are described. Thermal band images are presented to demonstrate the occurrence of flow separation at the tip of an isolated island in the estuary and the characteristics of the resulting downstream eddy are investigated. Field data are used to interpret the observed eddy structure and to confirm that the eddy is delineated in the images because of the existence of a source tracer of cold water upstream of the point at which the tidal stream separates from the tip of the island. Upwelling of cold water induced by the rotational motion of the attached eddy is shown to be inhibited by the stable density stratification existing in the estuary under summer conditions. The dynamics of the eddies generated at the island are discussed in terms of the non-dimensional parameters controlling the flow and it is demonstrated that the effects of the background rotation of the Earth upon the flow dynamics are weak. The usefulness of the so-called equivalent Reynolds number and the island wake parameter in describing estuarine flows is discussed and it is shown that the spatial structures of the observed eddies suggest a horizontal eddy viscosity for the flow of about 102m2s−, which is of the same order as the values adopted by other workers for similar cases.

ISSN:0143-1161    

DOI:10.1080/01431169008955056

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Ground reflectance data of selected targets for calibration of a Landsat Thematic Mapper (TM) image of Wind River Basin, Wyoming, acquired November 21, 1982, were analysed. The calibration lines, one for each band, are derived from linear regression analysis of scatter plots of ground bidirectional spectral reflectance versus the Thematic Mapper (TM) scanner response. The field-measured reflectances were obtained with a portable spectrometer at 10 nm spectral resolution in November 1983. The empirical equations derived were used to predict the ground reflectance of five unknown targets scattered throughout the Wind River and adjacent Bighorn Basins. Subsequently, in July 1984, field measurements were made over these targets with field spectrometers and with a hand-held radiometer with filters matching those of the TM. The agreement between predicted and measured quantities, mostly within the uncertainties of the field observations, was obtained, suggesting that the ground reflectance properties of the areas studied were approximately the same in November 1982 and July 1984, and that, as suggested by visual inspection of the images themselves, the atmosphere during TM data acquisition was relatively homogeneous from place to place over the area of our field observations.

ISSN:0143-1161    

DOI:10.1080/01431169008955057

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Radiance data from a Landsat 5 Thematic Mapper image were used to study terrain effects in 284 4 pixel by 4 pixel quadrats in upland North Wales. The three semi-natural vegetation types examined responded differently to variations in slope and aspect. Short-croppedAgrostisgrassland was the most uniform type and it reflected radiation in a solar-orientated diffuse manner. Variations in radiance detected from two rougher vegetation types suggested environmentally induced heterogeneity within the vegetation cover, related to aspect (Nardusgrassland) or slope (Callunaheathland). The difference between reflected red and green light is proposed as a crude measure of photosynthesis that can discriminate between broad vegetation categories in undulating terrain.

ISSN:0143-1161    

DOI:10.1080/01431169008955058

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

This research was conducted to assess the utility of Landsat Thematic Mapper thermal data (10.4 to 12.5/μm) for urban feature analysis. Seven band thematic mapper data collected on 25 October, 1982 for the Chicago metropolitan area were used to determine the relative importance of the thermal band as a component of an urban land use classification.|Analysis consisted of: (1) the use of a transformed divergence measure (separability) to test the interclass spectral variability of selected features for different channel combinations and (2) a comparison of classification results, with and without thermal data using a supervised layered classification algorithm. The use of thermal data resulted in an overall 9.3 per cent increase in classification accuracy. Elimination of classes such as forest, asphalt and railroad resulted in an increase of 12.0 per cent in classification performance. Examination of the separability analysis and classification results indicated there were specific areas of success resulting from the use of thermal data. Increased classification accuracy occurred in several classes such as shadow (+ 36.7 per cent), residential ( + 41.1 per cent), active industry ( + 20.0 per cent) and commercial industrial fringe ( + 77.1 per cent). These results demonstrated that the information content of thermal data was valuable for urban area analysis.

ISSN:0143-1161    

DOI:10.1080/01431169008955059

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Sensor stripes evident in multisensor imagery can cause subsequent image classification to fail, if not removed properly. Of the destriping algorithms investigated, the one published by Horn and Woodham seemed to be the most promising, although, due to an inherent conceptual flaw, it can produce unexpected results. The problem with the original algorithm of Horn and Woodham arises from the fact that under certain circumstances it is extremely sensitive to statistically insignificant differences in the image data recorded by the individual sensors. This problem can be overcome by acquiring image statistics from homogeneous sub-images only.

ISSN:0143-1161    

DOI:10.1080/01431169008955060

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor