摘要:

Spatial variability of L-band (21 cm wavelength) microwave brightness temperature over a corn field, caused by spatial heterogeneity of soil hydraulic properties, is simulated by combining physically based models for microwave emission and for dynamics of soil water. The scaling theory is used for the spatial variability of soil hydraulic parameters, the scaling parameter being represented by a histogram corresponding to a log-normal frequency distribution. The mean and the standard deviation of brightness temperatures over a corn field are calculated as a saturated soil dries progressively under clear-sky conditions. Results are presented for two values for the coefficient of variation (CV)of the scaling parameter, namely 0·45 and 0·65, which encompass the range of a few available field observations. For CV=0·45, the mean brightness temperatures are higher and the standard deviations are lower by about 2 deg K compared with those for CV = 0·65. Results of the present simulation suggest that spatial variability of hydraulic parameters might not be an important consideration for interpreting mean brightness temperatures over reasonably large (a few hectares or larger)vegetated fields, although some information about the frequency distribution of hydraulic parameters would be needed in interpreting the standard deviation of the brightness temperature.

ISSN:0143-1161    

DOI:10.1080/01431168508948270

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

A numerical model has been developed for the purpose of explaining and quantifying the relationship between the SEASAT synthetic aperture radar (SAR)signatures and the bottom topography of the ocean in the Southern Bight of the North Sea and Nantucket Shoals. The model uses environmental data (wind, current and depth changes)and radar system parameters (frequency, polarization, incidence angle and resolution cell size)as inputs and predicts SAR-observed backscatter changes over topographic changes in the ocean floor. The model results compare favourably with the actual SEASAT SAR-observed backscatter values. The comparisons between the model and the actual data are all within 1·5 dB except for one limiting geometry. The model suggests that for bottom features to be visible on SAR imagery, a moderate to high current velocity (0·4 m/s or greater) and a low to moderate wind (between 1·5 and 7·5 m/s) must be present.

ISSN:0143-1161    

DOI:10.1080/01431168508948271

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Available LANDSAT and SEASAT images of the North American east and west coasts were analysed for internal wave patterns during the summer months of 1978. These images are from the satellite sensors: (i) multispectral scanner on board the LANDSAT satellite and (ii) synthetic aperture radar on board the SEASAT satellite. The Gulf of California during these months provided an excellent opportunity to compare the detectability of ocean internal wave patterns in these two sensors since the internal waves were tidally generated every 12·45 hours and cloud contamination in the LANDSAT imagery was negligible. Internal wave patterns were frequently visible in SEASAT imagery but only occasionally visible in LANDSAT imagery, a fact which cannot be explained by cloud contamination. Furthermore multiple wave packets with 12·45 hours spacing were observed from SEASAT but not always from LANDSAT. One possible reason for the infrequent detection of internal wave patterns from LANDSAT is that a specialized Earth-Sun-satellite geometry is required to image these waves.

ISSN:0143-1161    

DOI:10.1080/01431168508948272

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Digital SEASAT synthetic aperture radar (SAR) and LANDSAT multispectral scanner (MSS) data were evaluated to determine their utility to discriminate suburban and regional cover in the eastern fringe area of the Denver, Colorado, metropolitan area. The primary emphasis of the study was land-cover discrimination performance of MSS versus SAR and SAR/MSS combined. In addition, both a median-filtering and a data-smoothing procedure were tested in an attempt to increase the spectral separability between land-use/land-cover classes for SAR data. The results indicated that analysis of LANDSAT MSS data alone provided a significantly (α = 0·05) higher overall classification accuracy or improved spectral class separation than the best SEASAT SAR classification. However, when using LANDSAT MSS and SEASAT SAR data simultaneously, a significant increase in classification accuracy was obtained. Analysis indicated that SEASAT SAR data provided a measure of surface geometry that complemented the reflective characteristics of LANDSAT MSS visible and near-infrared data. Smoothing and median filtering provided significant improvement in classification accuracy over non-filtered SAR data.

ISSN:0143-1161    

DOI:10.1080/01431168508948273

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Recently, space-borne radar systems have been used to collect data for many different remote sensing applications. Some of the applications demand very high accuracy in the measured backscattering cross-sections. Microwave signals passing through the ionosphere may be, at times, affected by the scintillation effect, thus the backscattering cross-section. It is the purpose of this paper to discuss the gigahertz scintillation phenomenon and to assess the potential impact on active microwave observations.

ISSN:0143-1161    

DOI:10.1080/01431168508948274

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The performance of a ground-based microwave radiometer of new design to be used for remote sensing of the temperature profile of the atmosphere has been tested. It is continuously tunable in the range 52-8-58-8 GHz and has a high absolute accuracy. The radiometer measurements have been analysed with the statistical inversion method and the retrieved profiles have been compared with 28 simultaneous radiosoundings. The r.m.s. difference under clear-sky and cloudy conditions was, on these occasions, less than l-5degK up to 6km and 4km, respectively, less than OdegK up to 8 and 5-5 km, respectively, and less than 3-0degK up to 9 and 7-5 km, respectively. Methods to increase the profiling accuracy are discussed.

ISSN:0143-1161    

DOI:10.1080/01431168508948275

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

In this study, we examine the systematic and random variations in recorded radiance in two of the LANDSAT Thematic Mapper bandpasses for images obtained over a uniform agricultural area before and after harvest. Large variations will affect the accuracy with which conclusions may be reached regarding ground cover from an analysis of recorded multiband radiance data. We found the variations to be sufficiently large to suggest a need for caution in the quantitative analysis of multichannel digital radiance data to discriminate terrestrial cover types.

ISSN:0143-1161    

DOI:10.1080/01431168508948276

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Recent studies in the Republic of Niger have demonstrated that information acquired from the interpretation of satellite imagery can play a significant role in the planning, management and implementation of highway maintenance or rehabilitation in developing countries. In addition to assisting overall alignment and design review, LANDSAT MSS data proved invaluable with respect to understanding physical causes of pavement failure and the engineering options required to overcome repetition of similar problems in the future.

ISSN:0143-1161    

DOI:10.1080/01431168508948277

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

ISSN:0143-1161    

DOI:10.1080/01431168508948278

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor