ISSN:0143-1161    

DOI:10.1080/01431169608948983

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The purpose of this study is to assess the potential of estimating the area, age and changes of tropical secondary forest regrowth from the Landsat Thematic Mapper (TM). Sites of mature forest, agriculture, pasture, pasture with remnant trees, and stands of secondary forest regrowth from 2 to 19 years of age were surveyed in two study areas near Manaus, Amazonas, Brazil, and mapped to the TM imagery. Considerable changes in spectral reflectance were observed over the first 19 years of regrowth, and these can be summarized by indices related to canopy brightness and greenness. The near-infrared reflectance, the difference index, Kauth-Thomas greenness, and percentage leaf cover all increase over the first 4 years after abandonment, peak from 4 to 8 years, and decrease from 8 to 13 years. The Normalized Difference Vegetation Index (NDVI) rapidly rises over the first 4 years, and displays no apparent relation to stand age thereafter. The brightness of regrowth canopies decreases from 8 to 13 years. Stands from 13 to 19 years-old are spectrally similar to mature forest. All regrowth age classes are spectrally distinct from agriculture and pasture, and all regrowth age classes younger than 14 years are spectrally distinct from mature forest. Spectral indices of canopy brightness are significantly correlated with regrowth stand age (r2≤0·48,p<0·001). Based on field research in several areas of Amazonia, these spectral patterns can be explained in terms of temporal changes in canopy geometry and leaf area. The estimated rates of regrowth clearance and reversion to regrowth between 1988 and 1991 suggest the intensity of rotational agriculture practised by both communities. These results suggest that monitoring tropical secondary regrowth with TM imagery could substantially improve estimates of carbon sequestration subsequent to tropical deforestation.

ISSN:0143-1161    

DOI:10.1080/01431169608948984

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Remote sensing techniques have been used to segregate different forest types and three density classes in the Darjeeling, Jalpaiguri and Cooch Behar districts of North Bengal, West Bengal, India using IRS-1A LISS II data relating to November 1991. The results demonstrated the capability of satellite remote sensing to delineate pure sal, bamboo/mixed, riverain, coniferous and alpine forest types along with plantations through normal/stratified classification approaches. The stratified approach is proved to be superior to other traditional classification techniques. The forest cover of North Bengal was 26·2 per cent and the accuracy estimation by different methods demonstrated an overall accuracy of more than 85 per cent in segregating forest classes and 80 per cent in case of landuse/landcover classes.

ISSN:0143-1161    

DOI:10.1080/01431169608948985

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A method has been developed for controlling the quality of continuously updated forest information by satellite remote sensing. In this work Landsat Thematic Mapper (TM) satellite data, used as an economic repetitive form of information, was combined with continuously updated field information. The aim was to direct field inspection on to areas where updating had been absent or erroneous. The multi-temporal Landsat TM image was radiometrically calibrated by band to band regression. In the change classification, changes between the acquisitions were detected by standwise linear nonparametric discrimination. The correct classification percentage was 98 on mineral soil and 91 on peat land. When comparing the image classification results to recorded treatments, 6·9 per cent of stands were recommended for field inspection within a 2-year test period due to unrecorded manmade or unexpected natural change. For a 10-year inventory cycle, this means a recommendation for inspection of only one third of the stands when compared to present updating using repetitive total field inventory.

ISSN:0143-1161    

DOI:10.1080/01431169608948986

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Large area land cover mapping is an important application of remote sensing. A digital land cover map of Great Britain has recently been compiled by supervised classification of Landsat Thematic Mapper data. The work has involved development of a range of post classification procedures to correct contextual errors associated with the use of spectral classification algorithms. This paper describes these procedures and examines their effects upon the map product including a comparison with field survey data.

ISSN:0143-1161    

DOI:10.1080/01431169608948987

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The use of satellite images for mapping landscape and biological diversity in the Ferlo region of Senegal, in the Sahel ecoclimatic zone, was tested. A high resolution Landsat TM image was used for measurements of the landscape diversity. NOAA INDVI was applied for a yearly assessment of biomass production. These data were later correlated with avian diversity, which was used as an indicator of biological diversity. A model based on a combination of the two types of satellite images was used to explain 40-50 per cent of the variations in bird populations in the winters of 1991-1992 and 1992-1993. The model is suggested as a preliminary assessment for mapping and monitoring biological diversity in landscapes with large heterogeneity in the horizontal plane like the Sahel region.

ISSN:0143-1161    

DOI:10.1080/01431169608948988

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Rock expression in a multi-spectral image is referred to asmulti-spectral image facies. Thematic Mapper (TM) multi-spectral facies of sedimentary rock bodies outcropping in an overall arid area of northern Somalia were interpreted by: (1) comparison with laboratory reflectance spectra of weathered surfaces of rock samples from the study area; (2) considering the correlation between spectra of weathered and unweathered surfaces; and (3) petrographic analysis. Aerial photo analysis provided stratigraphic and morphological information.

ISSN:0143-1161    

DOI:10.1080/01431169608948989

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Exploiting the complementary characteristics of multi-source data for geological applications is particularly useful in lineament studies. Multi-source data integration requires rigorous correction methods to preserve the accuracy of the extracted information and the integrity of the composite image. This paper compares two geometric methods on Landsat TM and ERS-1 radar images: one is a photogrammetric method developed at the Canada Centre for Remote Sensing and the other is a polynomial method that is in general use. The superiority of the photogrammetric method, which accurately models the viewing geometry is demonstrated both quantitatively and qualitatively. This method achieved an accuracy of 30 m [vdot]ersus 45 m for the polynomial method on the TM images and 65 m versus 480 m on the radar images. Furthermore, it is shown that the residual geometric errors on the images rectified by the polynomial method modify the length, orientation and the number of extracted geological lineaments.

ISSN:0143-1161    

DOI:10.1080/01431169608948990

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Identification of active faults in Himalaya is extremely significant as they directly reflect the Himalayan continental collision. They have moved repeatedly during the Quaternary, resulting in the dislocation of many landforms, such as streams, alluvial and piedmont fans and river terraces, etc. In the present study, Landsat Thematic Mapper (TM) data has been used to identify signatures of Quaternary tectonics in parts of the Doon valley, NW Himalaya. The Siwalik zone is being squeezed between the very active Main Boundary Thrust and the Himalayan Frontal Thrust and there is differential uplift and subsidence in the Doon valley. The study has helped to extract certain subtle geological information which has played a significant role in the present geomorphic configuration of the valley. Apart from the many lineaments identified it was observed that a NNE-SSW trending lineament, identified distinctly on the satellite image, separates the Doon valley fan sequence from the Yamuna terraces in the west. It is inferred that the fan sequence has been uplifted and tilted towards the west. The analysis of remotely-sensed data along with selected field checks has yielded interesting results of the Quaternary tectonics experienced in the Doon valley.

ISSN:0143-1161    

DOI:10.1080/01431169608948991

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The diffuse attenuation coefficient is an essential parameter of a semi-analytical model of radiances used to process a remotely-sensed image for bottom mapping of coral reefs in French Polynesia. Spectral and wide-band values (SPOT-XS-1 and XS-2 and Landsat TM-1) or the diffuse attenuation coefficient were computed fromin situspectral irradiances measured with an underwater spectroradiometer in the ocean and in the lagoonal waters of two islands in French Polynesia. These data show that emerged zones may strongly influence attenuation, mainly at short wavelengths. Attenuation was also assessed statistically in two different ways from a SPOT image of the island of Bora Bora. This image was then processed to obtain a map of the bottom corrected for water column effects.

ISSN:0143-1161    

DOI:10.1080/01431169608948992

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor