摘要:

In this paper, colocated, near simultaneous measurements of ocean surface wind speed near the Indian subcontinent from the Special Sensor Microwave/Imager (SSM/I) and Radar Altimeter onboard, respectively, DMSP and Geosat satellites are analysed. It is found that for about 84 per cent of cases, difference of two winds is within 3 m s 1. However, when the colocated winds are averaged for entire period and over the grid boxes of 2.5 2.5, the correlation between the two winds appears to be very high. It is found that the absolute difference of the two winds has no apparent relation with the amount of water vapour and the amount of cloud liquid water present in the atmosphere. Further, the variations of absolute difference of two winds with SSM/I winds, altimeter winds and significant wave height have indicated that altimeter measurements of high wind speed are likely to be more inaccurate compared to SSM/I measurements. The variation of bias and standard deviation of the difference of the two winds as measured in each 1 m s 1 bin of altimeter wind indicated that the SSM/I wind and the Altimeter wind are in good agreement within 12 m s 1 of altimeter wind, and thus in this range any one can be used in the absence of another.

ISSN:0143-1161    

DOI:10.1080/014311698215955

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The algorithm for determination of effective emissivity of a cavity developed by Caselles and Sobrino ( Remote Sensing of Environment, 29, 135-146) has been proved to violate Kirchhoff 's law, and to give low values of emissivity. In this paper a Kirchhoff 's law-observing algorithm is developed, and comparison of the two algorithms is performed. Emissivity retrieved by our algorithm can be 1.5 times larger than emissivity calculated with the algorithm of Caselles and Sobrino. Although no significant difference is found between them for almost blackbodies (vegetated surfaces with large values of ground and vegetation emissivity), for other kind of terrestrial surfaces (bare soils and rocks) difference between the two algorithms can be up to 0.05 for a typical cavity.

ISSN:0143-1161    

DOI:10.1080/014311698215964

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

To take advantage of the high spectral resolution of Landsat TM images and the high spatial resolution of SPOT panchromatic images (SPOT PAN), we present a wavelet transform method to merge the two data types. In a pyramidal fashion, each TM reflective band or SPOT PAN image was decomposed into an orthogonal wavelet representation at a given coarser resolution, which consisted of a low frequency approximation image and a set of high frequency, spatially-oriented detail images. Band-by-band, the merged images were derived by performing an inverse wavelet transform using the approximation image from each TM band and detail images from SPOT PAN. The spectral and spatial features of the merged results of the wavelet methods were compared quantitatively with those of intensity-hue-saturation (IHS), principal component analysis (PCA), and the Brovey transform. It was found that multisensor data merging is a trade-off between the spectral information from a low spatial-high spectral resolution sensor and the spatial structure from a high spatial-low spectral resolution sensor. With the wavelet merging method, it is easy to control this trade-off. Experiments showed that the simultaneous best spectral and spatial quality can only be achieved with wavelet transform methods, compared with the three other approaches examined.

ISSN:0143-1161    

DOI:10.1080/014311698215973

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The Intensity Hue Saturation (IHS) transform, a popular image fusion technique to exploit the complementary nature of multi-sensor image data, can be expressed in spherical or cylindrical coordinates. This letter discusses the differences between both transforms with respect to image fusion.

ISSN:0143-1161    

DOI:10.1080/014311698215982

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The fuzzy ARTMAP has been applied to the supervised classification of multi-spectral remotely-sensed images. This method is found to be more efficient, in terms of classification accuracy, compared to the conventional maximum likelihood classifier and also multi-layer perceptron with back propagation learning. The results have been discussed.

ISSN:0143-1161    

DOI:10.1080/014311698215991

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A new supervised classification method is developed for quantitative analysis of remotely-sensed multi-spectral data. It is based on the comparisons of the probability density function of the mixture of three normal distributions for a pixel and the probability density functions of the mixture of three normal distributions for spectral classes. The comparisons are made according to the distances between them. The discriminant function, which takes values on the interval \[0, 2], is defined as Hellinger distance. The decision rule is established according to the values of Hellinger distances. The values of the discriminant functions give extra information including spectral similarity and difference percentages in the comparisons. This clarifies the classification results and could help researchers interpret better the classification results of remotely-sensed multi-spectral data.

ISSN:0143-1161    

DOI:10.1080/014311698216008

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

In remote sensing, a target generally has a random position and orientation with respect to the array of image pixels. We derive a simple analytic expression for the expectation value of the area of a rectangular target relative to the area of a square image pixel containing the target's centre point. The analytic result applies when the sides of the target and image pixel are parallel. We then consider the possibility of a random orientation of the target using a more general digital approach. Interestingly, we find that the analytic expression (ignoring orientational averaging) is quite adequate for practical applications.

ISSN:0143-1161    

DOI:10.1080/014311698216017

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A method for monitoring oil spills using SAR imagery is suggested, based on the simulation of the wave spectrum using modelled surface winds. A first order separation of the purely wind-driven backscatter distribution and its modification due to surfactant was made by parametrizing the effect of surfactant on the wave growth rate and on the reflective properties of the sea surface. The technique was applied to a SAR image showing the Sea Empress oil spill, in south-west Wales, UK.

ISSN:0143-1161    

DOI:10.1080/014311698216026

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor