ISSN:0143-1161    

DOI:10.1080/01431169508954496

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The principal components transformation is used to highlight areas that show a change in time, normally associated with fire damage and vegetation regrowth. These variations are enhanced in the high order components. The individual scenes, as well as the components, are classified by unsupervised techniques to yield thematic maps on which dynamic cover type classes are described. These maps are later compared with the resulting images of arithmetic operations, such as subtraction and ratioing.

ISSN:0143-1161    

DOI:10.1080/01431169508954497

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

There have been extensive evaluations of different remote sensing digital classification techniques. In contrast, there has been very little systematic evaluation of various enhancements, such as different colour composites, for visual interpretations. This study examined three Landsat Thematic Mapper (TM) colour composites for visual classification of agricultural crops in an Imperial Valley, California study area. Accuracy results varied considerablywith the composite from the best three bands as determined by transformed divergence calculations being more useful than an image obtained via principle components or the standard infrared simulated false colour composite.

ISSN:0143-1161    

DOI:10.1080/01431169508954498

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The mixture of three normal distributions is proposed as a model for an area that we call a ‘class’ in a region according to the spectral brightness of three different band (pixel) values in remote sensing. The parameters in a mixture of three normal distributions arc estimated by the method of moments for grouped data. Newton-Raphson iteration method is used for estimating the parameters where all parameters are unconstrained. The method of finding suitable starting values for Newton-Raphson iterations is also given. A computer program is developed for this purpose.

ISSN:0143-1161    

DOI:10.1080/01431169508954499

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

A procedure developed for quantifying spectral variability was applied to visible and near-infrared spectra from a database of the Wind River and Bighorn basins. Principal Components Analysis (PCA) of 94 sedimentary rock spectra distinguished shales, sandstones, limestones, dolostones, bedded gypsum and bentonites from 25 stratigraphic units. However, only twelve spectrally distinct groups were delineated because of lithological homogeneity. Albedo and slope characteristics of the spectra were found to be related to the first and second PC, respectively, and absorption bands related to the remaining components. A second PCA phase, using vertically scaled spectra to minimize the albedo variability, indicated space distributions that enhanced major absorption features in the ncar-infrared region. Parameters describing absorption bands were also calculated from spectral continuum. The best parameters for spectra discrimination were band depths at 1900, 2200 and 2300 nm, in agreement with the PCA results using scaled spectra. Finally, the stratigraphic column was characterized by correlated log sections composed by PC scores of the original data and of scaled spectra, in lieu of band, band-ratios, area and depths of absorption bands. Reflectance-lithostratigraphic markers were identified in the log sections and indicated the potential of reflectance-lithostratigraphy in correlation studies. We concluded that PCA using a small number of narrow bands to represent the spectrum was an adequate mathematical approach for spectral analysis. PCA of scaled spectra was found to be a useful tool to enhance differentiations due to absorption features.

ISSN:0143-1161    

DOI:10.1080/01431169508954500

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The Shillong plateau in north-east India shows innumerable fracture lineaments on satellite images. In fact the whole plateau is criss-crossed by fractures. The plateau has been subjected to extensive compressional forces mainly in N-S and E-W directions resulting from the collision of the Indian plate with the Tibetan and Burmese plates, respectively. This type of plate tectonism has been responsible for the formation of many significant faults, folds and other tectonic features in the Shillong plateau and adjoining regions. The well known E-W trending Dauki fault, N-S trending faults, NE-SW trending shear zone and other prominent lineaments and their associated structural features could be studied on the basis of remote sensing techniques. Folding in soft sediments along the Dauki fault reveals the compression direction. Directional compressional tectonism has been expressed through lateral movements along the NE-SW trending shear zone and N-S trending faults and folds in the area just south of the Hatlong thrust. It has been observed from the studies that the Dauki fault zone and the areas in Bangladesh show various tectonic features, which are mostly controlled by vertical movements. Seismicity of the Shillong plateau is quite scattered all over the area. The occurrence of several deep earthquakes (> 1OOkm) indicate deep tectonic activities in the upper mantle. Earthquakes have been found to occur near some faults and this is probably an indication of recent activities along these faults.

ISSN:0143-1161    

DOI:10.1080/01431169508954501

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Airborne videography is a useful way of producing very high resolution remotely-sensed data. Before video data can be used for digital analysis, individual frames must be correcled for geometric distortion and brightness variation. The most obvious geometric distortion occurs because the odd and even fields in a video frame are collected sequentially and can be displaced relative to each other by aircraft roll and forward motion. We describe a procedure for correcting this distortion based on the cross-correla lion between individual fields at different spatial lags. Brightness variation across frames occurs because of dilTerences in viewing geometry, bi-directional reflectance variation and atmospheric scattering. We describe a method for removing much of this variation by calculating scattering angle across the image with an optional adjustment for sensor plane tilt. Relations between scattering angle and scene brightness statistics may then be calculated from sequences of images collected along a given transect. These relations can be used 10 normalise brightness. Tests of normalisation procedures based on mean, standard deviation, and median brightness show that the median gives the best results. This approach also produces better results than commonly-used band ratioing procedures.

ISSN:0143-1161    

DOI:10.1080/01431169508954502

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

We have tested a method utilizing Landsat-TM and SPOT high resolution images to study a geodynamically active zone characterised by major geothermal activity. Analysis of the imagery permits better understanding of the patterns of spatial distribution of the geothermal fields of the Taupo Volcanic Zone (TVZ) in which some en echelon structures are linked to major crustal faults resulting from subduction. Automatic classification techniques have been developed as well as a specific study of the thermal spectral region (Landsat-TM band 6) which, despite poor spatial resolution (120m), provides information about geothermal activity at the local scale. The study reveals the value of Landsat-TM band 5 (middle reflective IR, 1·55urn- 1·75 pm), notably by the 5,4, I (red, green, blue) combination which identifies vegetation associations in geothermal areas. In addition, the images assisted mapping of volcanic deposits and structures associated with the Tarawera Rift which formed in 1886. Based on our analysis of high spatial resolution satellite images, this appears likely to be a key technique to help understanding deformation in this region.

ISSN:0143-1161    

DOI:10.1080/01431169508954503

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Satellite remotely-sensed sea surface temperature (SST) data were obtained during the initial phase of the onset of the south-west monsoon in the north-western Indian Ocean for the years 1987and 1988. Large wedge-like areas of upwelled water during 1988 were observed at 5°Nand 10°N after the Somali current spinup, indicative of a two-gyre circulation in the Somali current system. Satellite infrared observations of the Bay of Bengal during the early February 1990revealed the existenceof two bands of warm water that resembled a western boundary current (WBC) along the east coast of India. A warm core eddy, with a major axis of nearly 120km, appeared at 89°E and 19°N at the end of the axis of the current. The existence of the two gyre system ofT the Somali coast and the presence or absence of the WBC in the Bay of Bengal in response to the onset of the summer monsoon has been discussed in detail.

ISSN:0143-1161    

DOI:10.1080/01431169508954504

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The testing and evaluation of new observing systems (VHF–45MHz, UHF–961 MHz wind profilers) as well as their performance in a network was listed among the goals of the FRONTS87 European field experiment. Using the FRONTS87 dataset for the 12–13 January 1988 cold front, the two horizontal wind components from the INSU-METEO VHF and UHF wind profilers are' quantitatively compared with those derived from collocated special upper-air soundings. Comparison between the sounding and the protilers data shows good agreement with rms differences of 4–4·5 ms-1for the VHF and 2·2ms-1for the UHF wind profiler. The combined use of the two profilers with their high timeresolution data (one vertical profile every 15min) along with the high altituderesolution data of the UHF profiler (150m) allowed us to obtain, in precipitation as well as in clear sky areas, a detailed image of both the low-level and upperlevel jet associated with the cold front observed over Brittany France, 12–13 January 1988. The case-study analysis illustrates the potential application of the French UHF and VHF wind profiling systems for describing synoptic and mesoscale wind regimes.

ISSN:0143-1161    

DOI:10.1080/01431169508954505

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor