ISSN:0143-1161    

DOI:10.1080/014311697218359

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Advantage is taken of a unique spectral feature of soil biogenic crust containing cyanobacteria. It has been shown that the special phycobilin pigment in cyanobacteria contributes in producing a relatively higher reflectance in the blue spectral region than the same type of substrate without the biogenic crust. A spectral crust index (CI) has been developed, based on the normalized difference between the RED and the BLUE spectral values: CI 1 (RED BLUE)/(RED BLUE). Applying the index to a sand dune environment, it has been shown that the CI can be used to detect and to map, from remote sensing imagery, different lithological morphological units, such as, active sands, crusted interdune areas and playas, which are expressed in the topography. As a mapping tool the CI image is much more sensitive to the ground features than the original images. The absence, existence, and distribution of soil crust are an important information for desertification and climate change studies. They are also highly valuable information for developing agricultural regions and/or infrastructures in arid environments since soil crusts contribute to soil stability, soil build-up, soil fertility, and to the soil water regime. The application of the proposed CI can be performed with imagery acquired by any sensor which contains the blue band. Currently, the most common data sources are colour aerial photographs and Landsat TM images as demonstrated in this paper. However, CI should be applicable to other sensors such as the SPOTVEGETATION, MOMS-2P, SeaWiFS and MODIS which will be available in the coming years.

ISSN:0143-1161    

DOI:10.1080/014311697218368

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The geological map of Rajpura-Dariba belt prepared from Airborne magnetic geophysical and Landsat TM data (20 January 1990) has been integrated with structural and magnetic anomalies data using a micro-computer based geographical information system known as GeoReferenced Area Management (GRAM) system for the identification of potential zones of base metal mineralisation. The spatial data analyses of the lineaments and lithology maps derived from Landsat TM data revealed the presence of a number of workable Pb-Zn mineralization in the NE-SW trending lineaments, including the well known Dariba mine. The integration of principal component images such as PC1 and PC2, and directional filter output of Landsat TM data with lineament maps disclosed a buried ridge having NW-SE trend in the western part of Rajpura-Dariba mineralized belt.

ISSN:0143-1161    

DOI:10.1080/014311697218377

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

As part of an on-going research in geological applications of remote sensing over the Red Sea Hills, Sudan, different image processing algorithms have been evaluated in context of geological mapping using Landsat TM data. IHS and Principal Component (PC) decorrelation stretching, among others, appear to provide the maximum geological information. The major basement rocks in the area include gneisses, varying compositions of metavolcano-sediments, mafic to acidic synorogenic plutons, and dykes. Basalt, rhyolite, and sandstone make the major Phanerozoic cover. IHS-transformed images, with substantially saturated colour, appear generally superior in discriminating the various rock units when three least correlated bands are used. Images obtained from PC decorrelation stretching, computed with reduced noise, have been more informative in distinguishing lithologies with subtle compositional difference. Structural information are well exhibited on both images and undocumented shear zones, prominent faults and lineaments of regional significance have been detected thereby improving the geological understanding of the area. The study testifies that using Landsat TM data PC and IHS decorrelation-stretching methods yield the best results for geological mapping in arid regions, by preserving morphologic and spectral information, and when combined, they can be very helpful for improvements in already mapped areas.

ISSN:0143-1161    

DOI:10.1080/014311697218386

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The island of Cyprus hosts one of the best preserved ophiolite sequences of the world: the Troodos massif. Lithologically the complex comprises a mantle series of ultramafic rocks overlain by gabbros and (plagio)granites. The crustal sequence consists of dyke swarms with two series of pillow lavas at the top known as the lower pillow lava and the upper pillow lava. Massive sulphide deposits, that have for long been exploited in Cyprus, occur at the contact between the lower and upper pillow lava series. This contact is difficult to map in the field. In this paper we explore the possibility of using advanced image processing techniques to discriminate the main lithological units to guide in mineral prospecting. A detailed field-spectral stratigraphic study forms the basis for the selection of potential spectral end-members characterizing the TM image used. It is shown that spectral angle mapping of TM data can provide mineralogical maps that compare favourably with known surface geology and provide insight in potential prosperous areas for mineral exploration when combined with standard hydroxyl and iron oxide mapping ratio images. Our work demonstrates how remote sensing can be used for mineral exploration at a reconnaissance stage in ultramafic terrains.

ISSN:0143-1161    

DOI:10.1080/014311697218395

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

In this paper we show some alternative classifiers to the widely used maximum likelihood (ML) classifier in order to obtain high accuracy classifications. The ML classifier does not provide high accuracy classifications when the training sets are high-overlapping in the representation space due to the shape of the decision boundaries it imposes. In these cases, it is preferred to adopt another classifier that may adjust the decision boundaries in a better fashion. This objective may be achieved with several non-parametric classifiers and by using the regularized discriminant classifier, as shown in this paper.

ISSN:0143-1161    

DOI:10.1080/014311697218403

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The non-Lambertian behaviour of soil surfaces depends on its roughness at micro-scale and larger scales, as well as on the incident angle of the direct solar beam on the surface. A geometrical model, taking into account the diffuse as well as the specular component of energy leaving soil surfaces in the visible and near-infrared, is used in the paper to describe the influence of soil surface roughness, caused by soil aggregates or soil clods, on the soil bidirectional reflectance distribution. A rough soil surface in the model is simulated by equalsized opaque spheroids lying on a horizontal surface. The model was tested in outdoor conditions on artificially formed soil surfaces made of two spectrally different soil materials: a mineral loam, and a loam with high organic matter content. The spectral data were measured by a field radiometer in the three SPOT (HRV) bands. The model predicts that at specific illumination conditions, soils surfaces with the highest roughness, expressed by the minimum distances between soil aggregates, can show lower variation of reflectance in the view zenith angle function than soil surfaces of a lower roughness.

ISSN:0143-1161    

DOI:10.1080/014311697218412

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Results are presented from a study of land cover mapping undertaken in a tropical hillsides environment. The study area is located in the foothills of the Cordillera Central of Colombia, where a conventional maximum likelihood classification was performed upon Landsat TM imagery. A comprehensive accuracy assessment procedure performed on the resultant land cover map suggested that relatively low rates of classification accuracy were achieved. However, reported accuracy levels were found to vary substantially, depending on the specific methodology used to generate them. This suggests that caution is needed when making comparisons between classification accuracy figures reported by different workers, unless their methodologies are also clearly identified. It is further argued that a low accuracy land cover map still makes a valuable contribution to our knowledge of this hitherto little studied environment, provided that its limitations are understood and respected.

ISSN:0143-1161    

DOI:10.1080/014311697218421

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A mediterranean vegetated coastal area has been classified on the basis of multi-temporal TM images and accurate field data. The latter was revealed to be particularly important due to the complexity of the area in terms of coverage degree, height structure of living vegetation and the occurrence of under-storey species. The recognition and classification of the different coenosis has taken into account that the spectral characteristics of vegetation depends on the season and on local climatic conditions. A major improvement in the spatial resolution of spectral data has been obtained by merging TM and SPOT-P by a RGB-IHS transformation that allowed an overall accuracy in the classification of 85 per cent to be achieved.

ISSN:0143-1161    

DOI:10.1080/014311697218430

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The goal of this research was to decompose polarimetric Synthetic Aperture Radar (SAR) imagery of upland and flooded forests into three backscatter types: single reflection, double reflection, and cross-polarized backscatter. We used a decomposition method that exploits the covariance matrix of backscatter terms. First we applied this method to SAR imagery of dihedral and trihedral corner reflectors positioned on a smooth, dry lake bed, and verified that it accurately isolated the different backscatter types. We then applied the method to decompose multi-frequency Jet Propulsion Laboratory (JPL) airborne SAR (AIRSAR) backscatter from upland and flooded forests to explain scattering components in SAR imagery from forested surfaces. For upland ponderosa pine forest in California, as SAR wavelength increased from C-band to P-band, scattering with an odd number of reflections decreased and scattering with an even number of reflections increased. There was no obvious trend with wavelength for cross-polarized scattering. For a bald cypress-tupelo floodplain forest in Georgia, scattering with an odd number of reflections dominated at C-band. Scattering power with an even number of reflections from the flooded forest was strong at L-band and strongest at P-band. Cross-polarized scattering may not be a major component of total backscatter at all three wavelengths. Various forest structural classes and land cover types were readily distinguishable in the imagery derived by the decomposition method. More importantly, the decomposition method provided a means of unraveling complex interactions between radar signals and vegetated surfaces in terms of scattering mechanisms from targets. The decomposed scattering components were additions to the traditional HH and V V backscatter. One cautionary note: the method was not well suited to targets with low backscatter and a low signal-to-noise ratio.

ISSN:0143-1161    

DOI:10.1080/014311697218449

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor