ISSN:0143-1161    

DOI:10.1080/01431168808954947

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Since SPOT is an operational and commercial remote sensing system, the quality or the data must be guaranteed during the whole satellite lifetime. Just after launch, during the so-called in-flightassessment period, the raw data quality was analysed and the parameters for the preprocessing ground-based system were determined. Then, the quality or the preprocessed image was controlled. During the operational period, the quality or the images is periodically analysed. The evolution or both radiometric and geometric image quality parameters since the SPOT launch is presented and discussed in this paper.

ISSN:0143-1161    

DOI:10.1080/01431168808954948

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Aerial video images of an agricultural test site were analysed using principal component analysis and image processing techniques. The site (six treatments and four replications of cotton, sorghum, cantaloupe, johnsongrass, pigweed and soil) was imaged using blue, yellow-green, red and infrared filters over the lenses of four black-and-white video cameras on 31 May and 24 July 1983. Separate principal component analysis procedures were applied to the May and July data as part of a methodology to assess data dimensionality and structure. Supervisedminimum Euclidean distance classification procedures were conducted on sets of data that consisted of all four principal components, the first three principal components, the first two principal components and the first principal component. Results indicated that the number of components required to represent the four band data sets accurately was three for the May data and two for the July data. Scatter diagrams of plant means for principal components 1 and 2 showed good potential for determining the relative level of plant development.

ISSN:0143-1161    

DOI:10.1080/01431168808954949

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

An easy-to-use tool for the selection of colours for density-sliced and classified single band images has been developed and implemented on a proprietary image processing system. Colours may be selected interactively from a range of displayed palettes, or chosen by the system, which maximizes the apparent distinction between them through the use of a uniform colour space.

ISSN:0143-1161    

DOI:10.1080/01431168808954950

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The aims of this paper are (i) to investigate the lowest-order adjacency effect and the effect of multiple reflections between the ground and the atmosphere on the Advanced Very High Resolution Radiometer (AVHRR) channel 1 and channel 2 reflectances and on the normalized difference vegetation index (NDVI) and (ii) to make a comparison between global irradiances calculated from two empirical relations, one theoretical and the other experimental. Derivation of the theoretical empirical relation for global solar irradiance is in accordance with Iqbal (1983) whereas the experimental empirical relation is taken from 'Singh et al. (1985).The effect of multiple reflection on each channel reflectance is about 1·2 per cent so that the NDVI is not affected by including a multiple reflection term in the atmospheric correction algorithm. The lowest-order adjacency effect in channel 1 is about 7 per cent and in channel 2 is about 5 per cent and the NDVI changes by about 0·5 per cent which is negligible. These results show that the multiplereflection and lowest-order adjacency effects can be ignored if one is interested in the NDVI. But such effects could be important if one is using reflectances, say, for scene classification. The variations of global solar irradiance with the solar zenith angle for both empirical relations are presented. These relations vary in a remarkably similar manner. However, the experimental relation underestimates global irradiance compared to the value obtained from the theoretical empirical relation. As a result of this, channel 1 and channel 2 reflectances differ by about 16 and 10 per cent, respectively. But the effect on the NDVI is only about 2·4 per cent.

ISSN:0143-1161    

DOI:10.1080/01431168808954951

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Abstract. This paper reports the results of a study of the foliar reflectance properties of lodgepole pine trees under mountain pine beetle attack which aimed to determine the sequence of changes which occur. The motivation for this study was to identify spectral regions showing the earliest signs of attack in order to choose spectral bands for airborne linear array sensors. Normal illumination, diffuse hemispherical reflectance spectra were obtained of needles from trees showing varying degrees of stress from beetle attack and for needles from unattacked trees for comparison. The more pronounced changes in the spectra were interpreted visually and compared to changes reported by other authors. The more subtle changes were studied by analysing variance methods. Three spectral bands (the green peak, red edge and near-infrared (NIR) shoulder regions) have been identified as most promising for detecting early effects of bark beetle attack. Three additional bands (the blue, red and NIR plateau regions) are identified as reference bands for calibration and comparison purposes. The difference between foliar reflectance of attacked and unattacked trees is found to be most significant in the visible and red edge regions for current foliage and in the NIR for previous foliage. A red edge red shift was observed in the spectra of current foliage from attacked trees, in contrast to red edge blue shifts associated with stress in other studies. The observed sequence of subtle to more pronounced changes cannot be explained qualitatively using current knowledge of the plant pigment and anatomical changes which occur at the cellular and needle levels in stressed conifers. Further study of the detailed changes in pigments anel cellular and foliar anatomy is recommended, both to elucidate on the cause-and-effect relationships which occur, and to indicate the extent to which this paper's findings can be generalized. The findings suggest that multispectral linear array airborne scanners may be able to detect stressed conifers long before the red attack stage, but further investigation is required to determine whether the differences at foliar level between attacked and unattacked trees can also be detected at the whole-tree level, and whether confusion with other ground cover types can be avoided.

ISSN:0143-1161    

DOI:10.1080/01431168808954952

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Grazing animals have been responsible for changes in vegetation and for widespread erosion in Australia's arid zone. To minimize these adverse changes and to manage the intensity ofland use in relation to land capability, it is necessary to have information on the distribution and intensity of grazing and trampling, both of which are highly uneven. This paper describes a way of modelling the distribution of grazing and of generating the pattern of movement by cattle in a large paddock in central Australia for a particular configuration of watering points, fence lines and vegetation types. The method uses Landsat Multispectral Scanner (MSS) data and a cattle distribution model based on the convection—diffusion equation. The model relates the number of animals grazing to distance from water and preference for particular vegetation types. The solution to the conveetion—diffusion equation is the inverse Gaussian density function which can be used to calculate the total number of animals at a particular distance from water. The number of animals in individual grid.cells at that distance may then be generated from observed probability distributions. The cattle distribution model has to be fitted and is first derived from observed data for wet, dry and average rainfall conditions. A procedure is then described in which background changes in MSS band 5 over time and those due to grazing are separated on the basis of distance from water and vegetation type. The band 5 grazing effects provide a surrogate measure of grazing intensity and are used to estimate preferences for different vegetation types and to calibrate the animal distribution models. The results are very similar to those obtained from observed cattle distributions. The models may be used predictively to determine the effect of different watering point and fence line locations. Patterns of movement are determined by assuming that animals take the shortest paths from their grazing areas to water and cumulating the number of animals following each path. The patterns of movement derived from Landsat band 5 data are very similar to those determined from observed cattle distributions.

ISSN:0143-1161    

DOI:10.1080/01431168808954953

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

One of the difficulties encountered in dealing with AVHRR imagery is that of navigating the data with an acceptable degree of precision. This paper describesa method, based on satelliteephemeris, which allowsaccurately gridded hard copy images to be produced in an easily reproduceable manner.

ISSN:0143-1161    

DOI:10.1080/01431168808954954

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

ISSN:0143-1161    

DOI:10.1080/01431168808954955

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The Hough transform is a technique commonly used in the field of computer vision for detecting linesand shapes in digital imagery. The application of this method to the detection of circular geological structures in Landsat MultispectralScannerimageryis described. The method wassuccessful in identifying most of those features apparent to the human analyst, in addition to a number of errors of commission. It is proposed that the error rate is tolerable for this particular application.

ISSN:0143-1161    

DOI:10.1080/01431168808954956

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor