ISSN:0143-1161    

DOI:10.1080/01431169608948769

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Improvements in optical remote sensing spectral resolution and increased data volumes necessitates the development of improved techniques for quantitative geological analysis. Laboratory spectral studies indicate that absorption band positions, depths and widths are correlated with diagnostic physicochemical mineral properties such as composition and abundance. Most current analytical techniques are incapable of providing comprehensive quantitative analysis of hyperspectral geological remote sensing data. Factors which must be considered for hyperspectral remote sensing campaigns include spectral resolution, analytical technique, band pass positions and spatial resolution. In many cases the volume of data required to address specific issues can be reduced through intelligent selection of band passes and analytical techniques.

ISSN:0143-1161    

DOI:10.1080/01431169608948770

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

This study evaluates in detail the indicators of desertification process in semi-arid lands by making use of temporal satellite information along with the surface and statistical data with the aid of a GIS. The indicators were correlated to the surface information to establish the severity of desertification and factors helping the desertification process to continue. The results show that the process is a natural phenomenon but is aggravated by human activity.

ISSN:0143-1161    

DOI:10.1080/01431169608948771

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A method to estimate the pure reflectance of landscape components in mixed pixels is presented in this paper. Based on the usual linear mixture model, this original method allowed us to restitute the temporal and spatial variability of the reflectance of the components of a NOAA-AVHRR scene. Ground cover proportions were obtained from a SPOT image classification degraded at NOAA resolution. The signal deconvolution was made using blocks of pixels to limit the errors due to the misregistration between NOAA and the ground cover images. The model was applied to NOAA-AVHRR simulations and to actual NOAA temporal series (1992) over the HAPEX-Sahel degree square, to deconvoluate the reflectances of the three landscape components (millet, fallow and plateau). The data analysis indicated a high sensitivity of the method to the misregistration and the need to define an optimal size of pixels which provide a good compromise between the misregistration errors and the spatial variability of the reflectance components. The deconvoluated reflectances were compared to airborne measurements acquired over two sites during the HAPEX-Sahel experiment. The quality of the results depends on the type of landscape. The model performs best on a landscape with small surface units, well spatially distributed.

ISSN:0143-1161    

DOI:10.1080/01431169608948772

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Considerable work has been done on estimating daily fluxes at the regional scale from thermal data acquired in the early afternoon using semi-empirical models. But these studies have dealt only with clear days and homogeneous surfaces. We evaluate the use of some of these models under variable climatic conditions. A campaign of micrometeorological measurements performed from May to October 1993 on a small agricultural catchment in Brittany (NW France) allowed us to monitor the water budget and fluxes of three characteristical surfaces (meadow, wheat and stubble field). Thermal images covering the whole catchment were acquired on 7 August 1993 using an infrared camera aboard a small aircraft. They were corrected for atmospheric effects with the LOWTRAN 7 model. After geometrical corrections to superimpose these images on a digitilized land use map, a mapping of surface fluxes at the catchment scale is proposed and discussed.

ISSN:0143-1161    

DOI:10.1080/01431169608948773

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Coarse resolution products of maximum value composite NDVI data, derived from the AVHRR on board the NOAA-7, -9 and -11 series of polar-orbiting satellites, are becoming increasingly available. One such product is the ARTEMIS African decadal NDVT data set, available on CD-ROM for the years 1981 to 1991. These data have inherent spatial and temporal errors which arise as a result of the sampling procedures involved in their generation. This paper describes the way in which the ARTEMIS NDVI data are produced. It then describes the spatial and temporal accuracy of the data, estimated for a study area in East Africa, in terms of: 1. their spatial resolution, 2. pixel locational errors, 3. sampling biases and systematic errors introduced during the production of the data, and 4. the presence of signal noise in multi-temporal profiles of the data. The paper concludes that these errors may prove a considerable limitation to the usefulness of the data for distinguishing specific habitats on the ground over small study areas, and that in the further development of applications for these coarse resolution data sets, these errors must be taken into consideration.

ISSN:0143-1161    

DOI:10.1080/01431169608948774

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Canonical correlation analysis was used to examine the relations between the six reflective Thematic Mapper bands and six forest structural variables for 70 lodgepole pine forest stands in Yellowstone National Park, U.S.A. Two significant canonical variate pairs were extracted, accounting for 96·4 per cent of the total information in the overall canonical correlation analysis. Results of the canonical redundancy analysis indicate that 78 per cent of the overall unstandardized variance in spectral data is explained by the first two spectral canonical variates, while the first and second biotic canonical variates explain 59 per cent and 5·9 per cent of the raw variance in the spectral data. The first two biotic canonical variates collectively explain 59 per cent of the raw variance in the biotic data, and the first and second spectral canonical variates explain 41 per cent and 6 per cent of the raw variance in the biotic data, respectively. Height, live basal area, leaf area index (LAI), and size diversity are highly intercorrelated and act in combination to affect the overall reflectance, or brightness, of a forest stand. Overstory live density and understory total living cover relate strongly to stand greenness, particularly TM band 4.

ISSN:0143-1161    

DOI:10.1080/01431169608948775

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The reference sample plot (RSP) method is a distance-weightedknearest neighbour estimation method, which allows simultaneous interpretation of several variables. In the RSP method, thekspectrally nearest field plots are looked at separately for each unknown pixel, and the area weight of the unknown pixel is divided as a function of the spectral distances to the nearest plots. The RSP method was examined in a forest inventory for estimating stem volumes by tree species groups using different satellite materials. Two methods were tested both in searching for and weighting the nearest field plots. Euclidean distance functions worked steadily with all the volume variables studied. The other distance measure tested was based on regression modelling. With more than 15 plots, both covariance weighting and inverse distance weighting gave similar results. Considering the field data of this study, the suitable number of the nearest plots in plotwise estimation appeared to be between 10 and 15 plots. With Landsat TM, SPOT XS and SPOT P, the differences in standard errors were minor. When combined TM and SPOT P were used, the plotwise standard error of total volume was still over 60 per cent.

ISSN:0143-1161    

DOI:10.1080/01431169608948776

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The spectral separability of thirteen topical vegetation classes, including twelve forest types, was assessed. Although the thirteen classes could not be classified to a high accuracy the results of a set of supervised and unsupervised classifications revealed that three groups of classes were highly separable; a classification of the three groups by a discriminant analysis had an accuracy of 92·20 per cent. These three spectrally separable groups also corresponded closely to ecological groups identified from an ordination of data on tree species contained within a detailed ground data set. On the basis of the class separability analyses the three spectrally separable groups were mapped, with an accuracy of 94·84 per cent, from Landsat TM data by a maximum likelihood classification. It was apparent that some of the errors in this classification could be resolved through the use of contextual information and ancillary information, particularly on topography.

ISSN:0143-1161    

DOI:10.1080/01431169608948777

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Eco-climatic classifications have proved to be of great utility for the planning and management of various agricultural and forestry activities. Since the usual methods are often expensive and not easy to apply, remote sensing data processing has recently been proposed to identify ecologically homogeneous land units. NOAA AVHRR data in particular have been demonstrated to be suitable for this purpose thanks to their spatial resolution and frequent acquisition. While most works in this field have dealt only with NDVI imagery, it has been suggested that thermal and ancillary data could also bring significant information. These considerations have been kept in mind during the present study, which concerns the eco-climatic classification of a complex Italian Region by the use of NOAA NDVI and thermal images from two years in addition to ancillary data. A complete methodology was developed for the processing of this integrated data set with particular reference to the identification of the suitable numbers of main and sub-classes. The final output was compared to existing climatic and land use information about the region. The substantial agreement between these sources testifies to the eco-climatic value of the product obtained.

ISSN:0143-1161    

DOI:10.1080/01431169608948778

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor