ISSN:0143-1161    

DOI:10.1080/01431169208904138

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

A predictive model of water quality variables has been developed for SPOT-1 imagery, and applied to Lake Patzcuaro, Mexico. By using canonical and principal component analysis it is shown that, at most, two water quality variables, suspended solids and chlorophyll-a concentration, can be derived from the SPOT data. Having established the independent predictiveness of a set of empirical relations between the SPOT data and the water quality variables, the whole lake was analysed to reveal the spatial distribution of suspended solids and chlorophyll-a. It was revealed that a very serious algal bloom had occurred. No bloom of such intensity has ever been observed before or suspected to have occurred in Lake Patzcuaro. The applicability of SPOT imagery to water quality monitoring is clearly demonstrated.

ISSN:0143-1161    

DOI:10.1080/01431169208904139

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Landsat-5 data provide information related to bathymetry and bottom type variations as registered by three water-penetrating bands. In this study, band 1 and band 2 data were used for mapping of subtidal coastal habitats in the Abu Ali Bay, Gulf Coast of Saudi Arabia. The method used here is based on eigenvector rotation of the two bands to enhance bottom type variations. The eigenvector rotation reduced the effect of water depth variations on bottom types. The results are presented as a colour-coded image showing five major habitats in Abu Ali Bay.

ISSN:0143-1161    

DOI:10.1080/01431169208904140

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The subwindowing method of modelling synthetic-aperture-radar (SAR) imaging of ocean waves is extended to simulate the imaging of two-dimensional wave trains. Simulated images show that the azimuthal smearing induced by random wind waves reduces the image response to swells that are primarily imaged by velocity bunching. The magnitude of this effect is not accurately predicted by degrading the SAR resolution using a scene coherence lime. The smearing does not depend on the wind direction when imaging swell, and does not affect the imaging of range travelling swell. Theoretical analysis shows that adjusting the focus of the SAR processor introduces an offset in the mapping of the surface scatterers that compensates the incoherent azimuthal propagation of the wave being imaged, leading to a higher image contrast. The focus adjustment yielding the maximum contrast is approximately one half the azimuthal phase velocity of the wave when it is propagating within 45° of the SAR flight direction. The dependence of the image contrast on focus setting predicted by image simulations agrees reasonably well with that observed experimentally. Azimuthal cut-off and range rotation of the spectral peak are predicted when the imaging of locally wind-generated wave trains is simulated. Comparison with other modelled results show that the velocity bunching and azimuthal smearing effects are strongly interdependent, and cannot be treated separately.

ISSN:0143-1161    

DOI:10.1080/01431169208904141

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Landsat Thematic Mapper and airborne Synthetic Aperture Radar (SAR) imagery acquired over an area of south-western Greenland are co-registered and analysed. Significant corrections to the SAR data were required to account for range-darkening, non-square pixel dimensions, speckle, and relief distortion. In one area, exposed rock was available for use as co-registration control, while in another area it was absent and supraglacial lakes and streams were used. The co-registered scenes highlight many differences between the optical and radar signatures of ice sheets.

ISSN:0143-1161    

DOI:10.1080/01431169208904142

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

A scheme is introduced which in effect 'splits’ Defence Meteorological Satellite Program (DMSP) single broadband sea ice reflectances into weighted visible and near-infrared (NIR) component reflectances. The method is rooted in (1) the fitting of polynomials to observed spectral reflectance curves of sea ice, (2) a weighting scheme and (3) the identification of general sea ice types and their corresponding areal coverage per imaged cell. Previously derived DMSP broadband sea ice reflectances in the Arctic Basin have been spectrally sequestered into visible and NIR component reflectances for May to August for the years 1977, 1979, 1984 and 1985. Comparison of spectrally modified DMSP visible reflectances (0-4-0-9 µm) are in closer agreement with NOAA-5 derived visible sea ice reflectances (0-52-0-72 µm ) than unmodified DMSP visible/NIR reflectances (0-4-1-1 µm ) for July 1977 in the Arctic Basin. It was also found that melt pond and flooding effects were more apparent for spectrally-modified NIR reflectances as compared to spectrally-modified visible reflectances. Possible uses of the scheme and newly created data sets are discussed.

ISSN:0143-1161    

DOI:10.1080/01431169208904143

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

A method is described for determining the fractal dimension of an ice sheet or other snow-covered surface from a Landsat-type image. The method relies on the well known strong correlation between surface slope and image brightness and it has been applied to a Landsat image of the ice cap on Nordaustlandet, Svalbard. Two transects approximately 100 km in length were studied, and they were found to give consistent results. The surface shows strong evidene of fractal behaviour on scales bclween 0’3 km and at least 10 km, with a fractal dimension of 1-120 for transects of one (topological) dimension This fractal behaviour was compared with that of the underlying bedrock, which also displays fractal behaviour over the same range of linear scales but with a significantly larger fractal dimension of 1 38. This difference accords with glaciologjcal theory.

ISSN:0143-1161    

DOI:10.1080/01431169208904144

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Since the advent of the first Landsat series of Earth resources satellites, many researchers have successfully mapped land cover types, especially in areas of low relief. However, in areas of rugged terrain these are complicated and only limited success has been reported. In this paper topographic effects have been analysed using a radiance model. The model was used to separate the illumination effect from the underlying land cover reflectance. The main thrust of the approach presented here is that, without using a digital terrain model, it is possible to separate the shading and spectral effect in the two indexing classifications by using the log transformations and band ratios applied to Landsat Multispectral Scanner data. The Landsat data were classified in terms of different land cover types found in the northeastern mountainous region of Tasmania, Australia.

ISSN:0143-1161    

DOI:10.1080/01431169208904145

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Time series of reflectances over the Valensole plateau test site (southeast of France) obtained from NOAA-9 Advanced Very High Resolution Radiometer (AVHRR) data show significant short-term variations over a three-month period. This paper demonstrates that the short-term variations are due essentially to surface bidirectional effects while atmospheric directional effects and other sources of fluctuations remain of lower amplitude. When the data are classified according to their viewing angles, in order to reduce the influence of directional effects, the consistency of the NDVI time series is strongly improved and its r.m.s. level of short-term fluctuations is decreased by a factor of 2, from 005 to 0025. Taking into account the effects induced by viewing angle variations should allow us to improve definitely the accuracy of the characterization and monitoring of the terrestrial vegetation.

ISSN:0143-1161    

DOI:10.1080/01431169208904146

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The use of a vegetation index in the study of vegetation changes requires that the influences of the signal gain, of atmospheric conditions and of soil be removed. This paper presents a theoretical basis for technique that theoretically removes all these influences from raw data without the use of external inputs. It produces a normalized perpendicular vegetation index that is suitable for vegetation change studies based on non-corrected radiometric data.

ISSN:0143-1161    

DOI:10.1080/01431169208904147

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor