ISSN:0143-1161    

DOI:10.1080/01431168608954687

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

A brief introduction is given to the field of remote measurement of the surface wind vector field over the ocean using radar scatterometry from satellites. A summary of the physical processes involved in the measurement is given, together with a review of recent studies to employ these data in numerical weather prediction modelling, and suggestions are advanced for some future simulation studies. The emphasis here is on the data obtained by SEASAT. The intent is that such data may be used to develop and refine integrated analysis programmes that can take increased advantage of the scatterometer data streams that are planned to be available from ERS-1 and N-ROSS commencing in 1989.

ISSN:0143-1161    

DOI:10.1080/01431168608954688

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The theoretical behaviour of the near-surface wind-driven currents is strongly dependent upon the models used to describe the mixed surface layer (especially the kinematic viscosity profile). This paper investigates measurements of ocean currents by HF Doppler radars in order to shed some light on this problem. It is found that the relative directions of the wind and current velocities and the variation of the current speed with respect to radar frequency (i.e. with respect to depth) are the most sensitive parameters to analyse for discriminating among the various models. The results of a preliminary experiment which was conducted in the western Mediterranean during the autumn of 1981 are presented. In this experiment the current was measured on 8 consecutive days at two radar frequencies corresponding to integration depths of 1 and 2 m, respectively. A special study shows that the near-surface current is only weakly influenced by the proximity of the coast (the measurements were obtained between 10 and 34km offshore). Because of the shortness of the experiment analysis of the wind-current relation does not provide the required accuracy whereas analysis of the current shear, which can process simultaneously the data obtained in nine different sea cells, gives a significant result supporting models with small shears (like Ekman's model with a constant kinematic viscosity profile). Some future improvements are briefly discussed.

ISSN:0143-1161    

DOI:10.1080/01431168608954689

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

This paper describes the terrain height measurement capability of synthetic aperture radar with an interferometer assuming the radar operates on a satellite. The interferometer phase measurement uncertainty due to additive thermal noise and multiplicative speckle noise, which determine the upper limit of the height measurement accuracies of this radar system, has been obtained by numerical simulation. The height measurement accuracies attainable on a relatively flat terrain areas are of roughly the same order as range resolution when C- or X- band radar is operated at an altitude of 300 km.

ISSN:0143-1161    

DOI:10.1080/01431168608954690

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The plantmetric errors due to terrain relief and atmospheric refraction must be considered when high geometric resolution sensors and off-nadir viewing angles are used. This paper presents an approach to correct these errors using an integrated procedure that takes into account geometric and radiometric effects, connected to simulations of future remote-sensing systems or precision data processing. A diagram shows the relation between the root mean square error of the digital elevation model necessary to correct the terrain relief effect and the achievable scale of the output image map. The procedure is currently applied to the SPOT simulation on the Basilicata test site in southern Italy. A short example is given to analyse the geometric errors involved.

ISSN:0143-1161    

DOI:10.1080/01431168608954691

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The aim of this paper is to estimate the effect of atmospheric contamination on SPOT satellite data for stereoscopic modelling by using data from the AVHRR instrument carried on the NOAA satellite series. This paper includes the development of an atmospheric correction algorithm for the visible spectral channel data from the AVHRR instrument, and an analysis of the atmospherically corrected AVHRR data from many successive days, bearing in mind that the SPOT data for stereoscopic modelling will be from two orbits which will be separated by several days.

ISSN:0143-1161    

DOI:10.1080/01431168608954692

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The data available in the LOWTRAN5 computer code are applied to short path lengths for radiation in the thermal infrared range during a particular survey. The resulting calculated value for the atmospheric transmittance is compared with an experimentally derived value.

ISSN:0143-1161    

DOI:10.1080/01431168608954693

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Indices of vegetation ‘cover’ and ‘greenness’ are derived for LANDSAT MSS digital data for an Australian range land type, and their usefulness discussed with reference to the information content of the data and the effect of shadowing asan interaction between landscape components. The indices are related to a class of statistical models called mixture models which provides a formal framework for analysing reflectance data from multicomponent surfaces.

ISSN:0143-1161    

DOI:10.1080/01431168608954694

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

This paper provides an initial investigation of the spectroradiometric data structure and information content of Thematic Mapper (TM) data for some Canadian forest-cover types. The Dryden-Lac Seul region in western Ontario is an important commercial and tourist area containing mainly boreal forest. A LANDSAT-4 TM scene of this region was analysed in conjunction with a considerable amount of ancillary data. The data were reduced to a manageable volume by selectingsubscenes;a preliminary attempt at atmospheric correction andradiometric calibration was then carried out; polygons representing a wide variety of cover classes were defined and, finally, the spectroradiometric information available for class discrimination was analysed using several techniques. Principal component analysis and feature selection reveal that the spectral data can be reduced to three eigenvectors with a loss of less than 10 per cent of the scene variance, and that the best three TM bands perform almost as wellas the first three principal components; for general cover-type discrimination, these bands areTM 3,4 and 5.TM bands 1,4 and 5 are marginally better for separating a set of softwood classes, although TM I has a very small dynamic range. The shortwave infrared (SWIR) spectral region, represented byTM bands 5and 7, seems to be particularly sensitive to forest vegetation density, especially in the early stages of clearcut regeneration. Shadowing is suggested as a factor at least as important as leaf moisture content in influencingthe spectral reflectanceof forests in this region. The first three principal components are related to the scene brightness (PC I), greenness (PC 2) and the contrast between the SWIR and the visible and near-infrared regions. We propose the name ‘swirness’ for the third component until a more complete understanding of its properties is achieved.

ISSN:0143-1161    

DOI:10.1080/01431168608954695

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

MSS, LAC, GAC and GOES data were used to delineate the extent of deforestation in Rondonia, Brazil, in order to identify those satellite data sources appropriate for monitoring deforestation on a continental/subcontinental scale. These data were processed to differentiate forest from non-forest (cleared, colonized areas) using two different classification procedures. The first procedure utilizes all available spectral bands of data in conjunction with a maximum likelihood classifier to discriminate cleared areas from primary forest. The technique is called probability thresholding. The second employs the red and nearinfrared spectral data to calculate a vegetation index which is subsequently thresholded from forest/non-forest delineation. Ground reference data were not available; the 80m (spatial resolution) MSS digital data products served as the reference data source. The 1·1 km LAC, 4 km GAC and 0·9 km GOES (visible band) images were compared with the MSS imagery. Areal comparisons indicated that (i) the LAC data are capable of adequately delineating colonization clearings in the Amazon; (ii) the spatial resolution of'uhe GAC data is too large to delineate linear clearings of varying length (tens to hundreds of kilometres) up to 2 km wide reliably, (iii) the visible GOES data were of little utility due to excessive data noise and (iv) probability thresholding procedures discriminated forest from non-forest more accurately than vegetation-index thresholding procedures. The results indicate that LAC data used in conjunction with probability thresholding offer the best data-source/classification-procedure combination. MSS data may be used when and where available as a ground reference data source in order to define the AVHRR threshold which most accurately discriminates cleared areas from primary forest.

ISSN:0143-1161    

DOI:10.1080/01431168608954696

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor