ISSN:0143-1161    

DOI:10.1080/01431169308953991

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The availability of environmental and Earth resources data acquired by satellites can assist all countries to gain a better understanding of how to safeguard their environment as well as ensure a more efficient management and productive harnessing of their natural resources, However, in order for the developing countries to share in the benefits inherent in remote sensing technology and in programmes related to environmental information systems, particularly through their participation in international, regional and national programmes and projects, there must be an adequate and long-term commitment to and an investment in the development of skills and knowledge in the discipline at the local level. This article focuses on the United Nations initiative to establish regional Centres for Space Science and Technology Education which should provide a unique opportunity for the development of such an indigenous capability. These Centres have the potential to contribute significantly to the implementation of the recommendations of the Rio Conference, otherwise known as Agenda 21 and to the successful execution of the programme of activities of the user communities in the developing countries.

ISSN:0143-1161    

DOI:10.1080/01431169308953992

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Surface temperatures of the FIFE (First ISLSCP Field Experiment) experimental area derived from thermal infrared radiances recorded from different satellite platforms at different scales were compared with reference observations by means of infrared thermometers at ground stations distributed over the area. FIFE was conducted during late spring, summer and fall over an area of 15 km by 15 km in a hilly tall-grass prairie region in northeastern Kansas. The data available for this purpose were produced by AVHRR and TOVS instruments aboard NOAA-9 and NOAA-10, the TM instrument aboard Landsat-5 and VISSR instrument aboard GOES-7. The scales covered by these instruments span a wide range, namely between hundreds of metres (Landsat TM) and hundreds of kilometres (TOVS). The data are analysed both with and without the application of an atmospheric correction.

ISSN:0143-1161    

DOI:10.1080/01431169308953993

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Panchromatic SPOT and Land sat Thematic Mapper (TM) data were merged using an IHS approach to receive a satellite composite as a basis for detailed geological mapping in the Gregory Rift of East Africa. The advantages of the new image product compared to SPOT-XS and ‘pure’ Landsat-TM images and the correlation between the spectral signatures received from the TM data and the mapped geological units are discussed. The Pleistocene to Holocene lava flows, tuffs and sediments of the Rift floor could be divided into several lithological units due to their different spectral characteristics and surface textures. Thus, by the help of the satellite image interpretation, in comparison to the official geological map of this area, the amount of lithological units could be doubled and 80 percent of the minor faults were mapped for the first time.

ISSN:0143-1161    

DOI:10.1080/01431169308953994

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Landsat MSS digital data provide an important means for the study of sand dune morphology and distribution, land cover change and desertification monitoring. Two images, one each of Landsat-l and Landsat-5 MSS were used to determine sand dunes, their change and desertification by human activities from 1973 to 1986. Five dune classes were observed: parabolic, barchan, longitudinal, transverse and sand sheet. Parabolic dunes and sand sheet are widely distributed and are dominant classes in this area. Other classes of land cover observed were canal, saline area, salt lake and protected plantation.

ISSN:0143-1161    

DOI:10.1080/01431169308953995

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Multi-spectral imagery from Landsat relating to the Karimnagar district of Andhra Pradesh, in South India was analysed using colour additive viewing techniques. The results were correlated with an existing soil association map prepared from aerial photo-interpretation with adequate ground truth. The four landscapes and their subdivisions that were identified on the soil map also could be identified on the Landsat map. An overall classification performance of 83·9, 82·4, 80·9 and 95·7 percent respectively has been achieved for rugged (R), undulating hummocky (U), very gently sloping (V) and river alluvium (A) landscapes. The best class performance was in the order of 95·7, 97·6, 81.8 and 95·7 percent and that of the lowest class performance of 50·5, 57·3, 70·1 and 95·7 percent for R, U, V and A landscapes, respectively. The overall combined performance of 85·7 percent has been achieved with respect to soilscape boundary delineations for all the four landscapes. The Student's t-test of significance revealed that for units R4, U4and V2the differences were significant and the rest were found to be nonsignificant. This study has demonstrated the usefulness of colour additive viewing techniques in the analysis of Landsat-MSS data for small-scale soil mapping and the same could be used for the preparation of small-scale soil maps of the States and the country.

ISSN:0143-1161    

DOI:10.1080/01431169308953996

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Collinear processing of Geosat altimeter data has been undertaken by several workers, many of whom have noted the problem of gaps in the data stream which can produce steps in the resultant height residuals due to repeat-specific orbit errors. The basic method of collinear analysis is explained and the problem of introduced steps discussed. A simple iterative method for significantly reducing this effect is presented, together with the resultant height residual profiles.

ISSN:0143-1161    

DOI:10.1080/01431169308953997

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The U.S. Navy's Geosat altimeter mission between 1985 and 1989 provided the first long-term measurements of sea surface topography with sufficient accuracy to observe large-scale changes in the ocean circulation. However, the overall accuracy of these measurements has been difficult to assess because of the lack of coincident measurements of the radar range corrections. In particular, Geosat, unlike Seasat, did not make simultaneous measurements of the range delay caused by refraction from atmospheric water vapour. This delay varies between 5 and 50 cm. In order to correct for this delay, estimates of columnar water vapour in the altimeter path are modelled using estimates from numerical weather forecast models or non-coincident satellite measurements. Comparisons of these estimates with direct radiosonde measurements have been made by others and clearly indicate a preference for the satellite measurement over the forecast model. NASA's Very Long Baseline Interferometry programme routinely estimates the wet tropospheric range delay at radio frequencies for all antenna locations at 15 minute intervals with a precision of a few cm rms. We have used these measurements to make a direct assessment of the Geosat wet troposphere range correction. The VLBI measurements show strong diurnal variations in columnar water vapour at several sites. These variations are a source of error (order 3 cm root-mean-square) in any non-coincident measurement of the wet troposphere range delay. These errors can be aliased to lower frequencies because of the satellite sampling scheme and have an effect on studies of annual and interannual changes in sea level with Geosat data.

ISSN:0143-1161    

DOI:10.1080/01431169308953998

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Current speckle filters attempt to restore the radar reflectivity using only the multiplicative speckle noise assumption. The best known filters, namely the Frost, Lee or Kuan niters are adaptive filters based on the local statistics, computed in a fixed square window. In this way, the speckle is reduced as a function of the heterogeneity measured by the local coefficient of variation. When the radar reflectivity undergoes significant variations due to the presence of strong scatterers or structural features (edges or lines) in the processing window, such speckle filtering is less effective. In this paper it is shown that the filtering process can be controlled both by the coefficient of variation and by various geometrical ratio detectors. Through shape adaptive windowing, these detectors allow the use of large window sizes for better speckle reduction while preserving spatial resolution and structural features. The backscattered intensity is modelled as

ISSN:0143-1161    

DOI:10.1080/01431169308953999

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The weighting filter is a new non-linear algorithm designed to reduce speckle noise in synthetic aperture radar (SAR) images and is presented in this article. Intrinsic similarities between this and the well documented sigma filter allow a useful quantitative comparison to be made that helps appraise the new technique. Implications drawn from these results, in both the real and Fourier domains, suggest that the new weighting filter may be a useful alternative when considering speckle suppression.

ISSN:0143-1161    

DOI:10.1080/01431169308954000

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor