ISSN:0143-1161    

DOI:10.1080/01431169608948753

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The August 1991 eruption of Mount Hudson, a volcano located in the southern Andes, spread 8 km3of ash into the atmosphere. As a result, a great part of the province of Santa Cruz, Argentina, was affected by a 0.1 to 10 cm ash layer. Plants and consequently animal life were severely touched and the region declared disaster-stricken. Comparison of pre- and post-eruption AVHRR images of the region show that at least a 70000 km2strip ranging from the Andes (Mount Hudson volcano) to the Atlantic coast has been affected. The NDVI was found to be more sensitive for the discrimination of affected areas than the raw AVHRR channels. Moreover, optimal timing for such an assessment is discussed considering the NDVI time profiles derived over the pre-eruption period. Visual analysis of the two post-eruption images available partly confirmed the ash removal date predicted by EPIC simulation model. However, both methods cannot be strictly compared since the diagnosis on whether ash remains or not, is sometimes hampered by the confusion between pre-eruption natural cover and ash. Furthermore, a time lag is necessary for vegetation to recover its initial vigour after the date of ash removal.

ISSN:0143-1161    

DOI:10.1080/01431169608948754

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A structural interpretation of aeromagnetic data of the Gabal Zubeir area, North Eastern Desert, Egypt, is presented. The average depth to the causative magnetic bodies within the basement complex (intrabasement) is determined in the form of aggregated bodies at two disturbing interfaces l.0km and 2.1 km depth through the application of two-dimensional power spectrum. Filtering, combined with analytical downward continuation on the two assigned interface has been carried out—this can assist in discriminating between shallow and deep anomalies. The structural elements affecting the basement complex at the two assigned interfaces with faults and folds (down-faulted and uplifted blocks) are delineated. The fault system is analysed in the form of azimuth-length frequency relations.

ISSN:0143-1161    

DOI:10.1080/01431169608948755

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Ras-Mohammed area located at the southern tip of Sinai, is an important and unique environment which has valuable resources that should be carefully maintained. This area is threatened by numerous anthropogenic activities. The most important risk is that associated with possible oil spills from tankers crossing the Suez canal

ISSN:0143-1161    

DOI:10.1080/01431169608948756

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Processing of Landsat-5 TM thermal images for lake surface temperature determination is addressed. A specific preprocessing algorithm to reduce sensor noise is presented and calibration and atmospheric correction is discussed. The atmospheric impact on thermal radiation measurements is modelled using Lowtran-7 utilizing radiosonde data. Comparing ground truth measurements acquired for 21 images between 1987 and 1994 with satellite derived temperatures yielded a mean square error of 0.53 deg K. A systematic overestimation or underestimation of Landsat derived temperatures was not found. The emissivity effect upon the accuracy of the derived surface temperature is discussed as well as effects of using alternate atmospheric profile data.

ISSN:0143-1161    

DOI:10.1080/01431169608948757

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Two simple modifications to the established sigma filter are proposed, and demonstrated to improve both its efficiency at smoothing speckle noise and its ability to preserve fine features. A fully automatic, unsupervised segmentation algorithm, based on the iterative application of the new filter, is described and successfully applied to ERS-1 Synthetic Aperture Radar (SAR) images of sea ice. The simplicity of this segmentation approach, together with its ability to segment classes separated by a gradual change in grey level intensity, may offer significant advantages over techniques based on edge-detection and region growing.

ISSN:0143-1161    

DOI:10.1080/01431169608948758

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The optical flow method is an approach to motion analysis in the field of computer vision. This method is implemented here to deal with rotational and deformational ice motion, for which the area correlation method shows deficiencies. The results show that the optical flow method has the capacity to cope with the rotation and deformation of an ice cover, while requiring less computing time than the area correlation method. For better representation of the discontinuities of a motion field, a modified version of the optical flow method is presented with the aid of image segmentation. The paper also includes a technique for detecting mean rotation and translation in terms of FFT transformation. In most cases, this technique can simplify and speed up the process of motion retrieval in the Arctic central pack ice area. The algorithm has been applied to fourteen pairs of images acquired in the Arctic Ocean and the Baltic Sea. Three of them are illustrated here to demonstrate the accuracy and other capacities of the algorithm.

ISSN:0143-1161    

DOI:10.1080/01431169608948759

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A study has been carried out using LOWTRAN-7 simulations of the Along-Track Scanning Radiometer (ATSR) data at 11 and 12 μm wavelengths to compare the merits of the multi-angle technique with those of the currently used multi-channel technique (split-window method) to retrieve both sea surface temperature (SST) and land surface temperature (LST). To this end a simple single-channel double-angle viewing model is presented, which relates actual surface temperature to the two brightness temperatures measured from space in the two views of interest (ATSR nadir and forward). Subsequently, statistical retrieval coefficients for the double angle and split-window techniques are derived via a regression analysis of the synthetic measurements. The results show that the double angle technique is capable of producing SSTs with a standard deviation of 0.23 deg K if the satellite data are error free and, furthermore, confirm the advantage of the double-viewing angle technique in comparison with the split-window technique for LST determination in homogeneous surfaces if the emissivity's spectral variation and the emissivity's angular variation, are of the same order of magnitude. Finally we present the preliminary results obtained using the proposed model from ATSR data over a semi-arid region of New South Wales, Australia provided by Prata, and over the Pacific Ocean provided by Barton.

ISSN:0143-1161    

DOI:10.1080/01431169608948760

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The mean square-root pair difference between the DN values of pixels separated by a particular spatial interval (lag) in a digital image is a measure of spatial variability related to the semi-variance. It is shown that this statistic, when evaluated in a local window for several lags differing in length and direction, can make an important contribution to the discrimination of classes of land cover. Square-root pair differences are, for this purpose, statistically preferable to semi-variances. It is also shown that a set of square-root pair differences measures different components of image texture, not all of which may be distinguished by simpler textural variables.

ISSN:0143-1161    

DOI:10.1080/01431169608948761

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

With the development in sensor technology, in recent years, spaceborne multi-spectral data with improved spectral, radiometric spatial and temporal resolution are now available to the user community. Higher spatial resolution provides more details about the Earth's surface features, compared to medium or coarse spatial resolution data by virtue of smaller instantaneous field-of-view (IFOV) at a given wavelength. This study aims at bringing out the additional information on soil erosion that may accrue from the interpretation of large scale i.e., 1:50000 Landsat Thematic Mapper (TM) analogue data over what could be derived from 1:250 000 scale. Owing to improved discernibility of eroded lands at larger scale the pockets of eroded lands as small as 2.25 ha could be mapped at 1:50 000 scale as compared to 56.25 ha that is possible from 1:250 000 scale data. Besides, substantial refinement in the delineated boundaries of these lands have also been observed. The approach and results are discussed in detail.

ISSN:0143-1161    

DOI:10.1080/01431169608948762

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor