ISSN:0143-1161    

DOI:10.1080/01431169208928580

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Remote sensing has traditionally been afforded only limited use in Arctic marine mammal research. This is primarily because the summers are short and often cloud covered; winters are long and solar illumination is limited to a few hours of twilight. Orbital sensors operating on a repeat cycle of 16 days simply do not offer the biologist a sufficiently reliable tool for habitat assessment studies. Compounding the data availability problem was the substantial entry cost to acquire and interpret digital remote sensing imagery. With the increase in computational power of microcomputers and the increasing availability of orbital remote sensing imagery (both the decreasing costs and increase in the number of available sensors) the utility of orbital platforms for Arctic marine mammal research should be re-examined.

ISSN:0143-1161    

DOI:10.1080/01431169208904033

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The relations of Scanning Multi-channel Microwave Radiometer (SMMR) 37 GHz polarization difference to precipitation and atmospheric carbon dioxide (CO2) concentrations are reviewed. Annual precipitation data, a surrogate for green leaf vegetation density, are compared with the coincident SMMR 37 GHz polarization difference from arid and semi-arid West Africa for 1982–85. The SMMR 37 GHz polarization difference was found to be poorly correlated with precipitation in arid and semi-arid zones, contrary to previous reports. Coincident SMMR 37 GHz polarization difference and atmospheric CO2concentration data from July 1981 to June 1983 are also reviewed. Previously suggested relations of the SMMR 37GHz polarization difference to atmospheric CO2concentrations were found to be heavily biased by winter conditions in the Northern Hemisphere. The use of the SMMR 37 GHz polarization difference for determining green leaf vegetation density, net primary production, atmospheric CO2draw-down and related processes is questioned.

ISSN:0143-1161    

DOI:10.1080/01431169208904034

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Spatial analysis of Advanced Very High Resolution Radiometer (AVHRR) data at Global Area Coverage (GAC) and High Resolution Picture Transmission (HRPT) resolution shows that structural information is detectable across a range of scales and that different biomes exhibit different detectable spatial characteristics. The spatial patterns observed in GAC and HRPT data are similar at coarse resolutions. Differences between the two are observed where point phenomena occur, and where scene objects are generally linear. The undersampling in GAC data generation can cause artificial contiguity and artificial disunity to appear in the image of any scene. The spatial structure observed in GAC image data must therefore be considered unreliable, at least at the scale of the GAC AVHRR resolution-cell size. However, the use of the spatial domain in studies of surface phenomena operating at scales greater than that of the resolution-cell size are unlikely to be limited by the undersampling effects. Indeed, the spatial temporal evolution of structure in AVHRR images may provide important indicators of regional environmental change.

ISSN:0143-1161    

DOI:10.1080/01431169208904035

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

A daytime image classifier, which relics on the difference in spectral signatures of the five channels of AVHRR, is proposed. The methodology is based on the preliminary classification of each pixel with the assumption that it is clear and on subsequent tests for cloud detection. The advantage of the preliminary classification is in that the threshold values for spatial variability tests are dependent upon the surface types identified thus allowing more data to be retained over some complex terrains. A fine dynamic cloud filter was designed with the assumption that the absolute value of the near-IR to visible reflectance ratio correlates negatively with surface temperature. The climatic thermal thresholds can then be updated using a clear observation encountered in an array of pixels. Application of the proposed technique is demonstrated on two examples with 1 km resolution AVHRR data and one example with a subset of sampled 30 km resolution AVHRR data from ISCCP. A quantitative validation is done by comparing the cloud amount from ISCCP C1-product with that derived using the present method for the same equal-area grid cells.

ISSN:0143-1161    

DOI:10.1080/01431169208904036

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

This paper describes the methodology developed to monitor the radiometric calibration of NOAA AVHRR data and to normalize succeeding polar orbiters for the International Satellite Cloud Climatology Project (ISCCP). Results are presented for NOAA-7, -8, and -9 Channel 1 (visible) data and briefly for Channel 4 (thermal infrared) in an appendix. The successful normalization of NOAA-8 and NOAA-9 to NOAA-7 allows the ISCCP calibration standard to be maintained over lime. A correction for the degradation of NOAA-9 data and an absolute calibration for the entire ISCCP dataset are presented.

ISSN:0143-1161    

DOI:10.1080/01431169208904037

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

A 100 km × 200 km region of the Sahetian zone of Africa was chosen as the place to demonstrate a new method of extracting hemispherical reflectance (albedo) from directional satellite data. Five NOAA-9 AVHRR daytime scenes in band I (0·58−0·68μm) were corrected for atmospheric variations to give the directional reflectances at the ground level. Using a stratification of the Gao region of Mali (Hiernaux 1989) based on soil texture, satellite data for homogeneous areas were selected. The number of view directions and the orientation of these varied because of the variable cloud cover and the changing orientation of the scanning radiometer with each overpass. These data were used in a knowledge-based expert system called VEG. This system is designed to handle a wide variety of kinds of input data. It contains an array of different techniques for inferring hemispherical reflectance. VEG accepted the spectral directional reflectance data, determined the best techniques for inferring spectral hemispherical reflectance, applied these to the selected sites and provided a rigorous estimate of the accuracy of the inference. VEG made all decisions and inferences using the input reflectance data and internal knowledge bases. The calculated directional reflectance factors at ground level were very similar to ground measurements reported in the literature. Furthermore, it was clear that a single nadir observation technique was always less accurate for estimating hemispherical reflectance than VEG using multiple view angles. The mean errors of the hemispherical reflectance of the entire region using VEG with multiple view angles and the direct nadir technique were 3 and 10 per cent, respectively, where the errors of the individual homogeneous areas were weighted by their relative sizes.

ISSN:0143-1161    

DOI:10.1080/01431169208904038

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The ATMOSATLAND interactive system based on an IBM-PC/AT for receiving and processing of HRPT/NOAA data is presented. The software allows the mathematical processing for determination of: (a) Baltic Sea surface temperature; (b) soil surface temperature of the river basins; (c) vegetation index; (d) urban heat islands; (e) environmental changes of mining areas; (f) radiation budget; (g) three-dimensional distribution of the atmospheric temperature, moisture and ozone. The ATMOSATLAND system is also provided for processing of SPOT, LANDSAT and KOSMOS digital images.

ISSN:0143-1161    

DOI:10.1080/01431169208904039

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Landsat-5 Thematic Mapper (TM) data of a subscene of Washington, D. C., were used to distinguish natural and man-made surfaces through analysis of their spectral response. Such information is needed to create and update geographical data bases at the national, regional and local levels. A quantitative measure of the separability and thus the ability to separate various surface features was calculated using the quantity known as divergence (D), a measure of the dissimilarity between two distributions. A general grouping of surface classes (nine) and a more specific set of classes (21), derived from the nine general classes, were studied. Discrimination between class pairs which were derived from a common class (such as, grass, mixed woods, pine woods, deciduous woods from the vegetation class) were surprisingly good. The asphalt and residential classes were the most difficult to separate/discriminate. The thermal band, TM band 6 (10·4−12·5μm) was found to improve the separability when replacing a visible band, but decreased the separability when included with the middle-infrared bands.

ISSN:0143-1161    

DOI:10.1080/01431169208904040

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

An unsupervised method is proposed for detecting circular structures on satellite images partly based on a version of the Hough Transform. This method consists of two major steps: the extraction of significant contours from the image, using mathematical morphology operators, and the detection of circular structures from the contours previously denned. The latter includes four substeps: individualization of the curves, decomposition of the curves into near-circular elements, application of the ‘adaptive HT’ version to each near-circular element, and computation of more precise results. As an example, the method is applied to a SPOT scene in Southern Peru to detect geological structures.

ISSN:0143-1161    

DOI:10.1080/01431169208904041

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor