摘要:

A simple method is derived for 1the determination of the two-dimensional surface image spectrum from the return signal of a synthetic aperture radar (SAR) without explicitly producing an image. The algorithm is similar in structure to a two-dimensional Fourier transformation, but the transformed function also depends explicitly on the wavenumber components. The function consists of the quadratic product of the complex return signal amplitude and the time-delayed complex conjugate return signal, the time delays with respect to range and azimuth time being proportional to the corresponding wavenumber components in these directions. The algorithm appears to be sufficiently simple to be implemented in real time aboard a satellite. Because of the considerable data compression achieved in reducing the original image to its statistical variance spectrum, this opens the possibility of obtaining global surface-wave spectral data from satellites without the excessive costs of sophisticated telemetry and a ground station network required for real-time line-of-sight transmission of the unprocessed signal data. The contracted signal-image-Fourier-transform (SIFT) algorithm may be interpreted as the application of the SAR as a continuous, two-dimensional Δκ (dual frequency) scatterometer. The difference frequencies arise through the multiplication of the chirped return signal with the time-lagged (i.e. frequency shifted) complex return signal. Since the return signal is chirped with respect to both range time and azimuth time, the introduction of two time lags corresponds to a two-dimensional Δκ modulation. The standard dual frequency scatterometer yields a modulation wave only in the radar propagation direction, but the basic principle of producing a beat wave by multiplying two chirped signals which are displaced in time relative to each other can be applied also to the azimuthal Doppler chirp of a broad beam dual frequency scatterometer. The generalized two-dimensional Δκ-scatterometer obtained in this manner differs from a SAR-SIFT processor only in the manner in which the spectrum of difference frequencies is generated: in a Δκ-scatterometer, the duration of the difference frequency sweep is normally large compared with the signal travel time, whereas in a SAR, the entire spectrum of difference frequencies is generated within a single pulse in a time shorter than the average signal travel time. The relative operational advantages or disadvantages of the two methods of obtaining microwave surface image spectra will need to be clarified in a more detailed technical analysis.

ISSN:0143-1161    

DOI:10.1080/01431168008948234

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The number of radiometric quantizing levels required for satellite monitoring of vegetation resources was evaluated by usingin situcollected spectral reflectance data, an atmospheric radiative transfer simulation model and a satellite sensor simulation model. Reflectance data were converted to radiance data; passed through a model atmosphere to an altitude of 706 km; and subsequently quantized at 16,32,64,128,256 and 512 digital count levels for Thematic Mapper bands TM3 (0·63-0·69 μm) and TM4 (0·76-0·90 μm), The simulated digital count data were regressed againstin situbiological data to quantify the relationship(s) between quantizing levels.

ISSN:0143-1161    

DOI:10.1080/01431168008948235

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

An automated technique is described, for extracting land-water boundaries from Landsat MSS images by means of ‘density contour-threading’ of the band 7 data. The resulting coastlines, etc. can then be transformed to fit any map projection—in particular the British National Grid—with the aid of selected ground control points.

ISSN:0143-1161    

DOI:10.1080/01431168008948236

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Microwave measurements on board Seasat during its 3 months of operation allow estimation of several important oceanographic and meteorological quantities to be made, including surface wind and wave fields. Since it was an experimental system comparison with conventional data is required. This note briefly reviews the measurements and describes some preliminary work in which high-quality data from the Joint Air-Sea Interaction experiment have been used to assist in the validation of each of the sensors.

ISSN:0143-1161    

DOI:10.1080/01431168008948237

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

This paper considers the problem of selection of dimensionality and sample size for feature extraction in pattern recognition. In general, the axes of the feature space are selected as the eigenvectors of matrices of the formR2−1R1whereR1andR2are real symmetric matrices. Expressions are derived for obtaining the changes in the eigenvalues and eigenvectors when there are changes of first order of smallness in the matricesR1andR2. Based on this theory, a method is developed for choosing the dimensionality of the patterns. Also expressions are derived for the selection of sample size for estimating the eigenvectors, for two gaussian distributed pattern classes with equal means, unequal covariance matrices and with unequal means and equal covariance matrices.

ISSN:0143-1161    

DOI:10.1080/01431168008948238

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Repetitive Landsat CCT data were used to monitor the motion of non-uniformly distributed suspended sediments in a New Zealand tidal basin. The movement of such suspended sediment was followed using all four MSS bands with non-uniformly distributed suspended sediment being differentiated from bottom features by the data from two satellite overpasses. As pan of this study penetration depths of 45-50±5 cm and 10-15 ±5 cm were found for channels MSS 5 and MSS 6 over the sediment-laden tidal inlet. The difference in penetration depths within each MSS band was ascribed to differing concentrations of uniformly distributed suspended sediments between the two overpasses.

ISSN:0143-1161    

DOI:10.1080/01431168008948239

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Digitally processed Seasat SAR imagery of the Denver Colorado area was examined to assess its potential for mapping urban land cover and the compatibility of SAR derived classes with those described in the U.S. Geological Survey classification system. The entire scene was interpreted to generate a small-scale land cover map. In addition, six subscene enlargements representative of urban land cover categories extant in the area were used as test sites for detailed analysis of land cover types. Two distinct approaches were employed and compared in examining the imagery—a visual interpretation of black-and-white positive transparencies and an automated-machine/visual interpretation. The latter used the Image 100 interactive image analysis system to generate land cover classes by density level slicing of the image frequency histogram.

ISSN:0143-1161    

DOI:10.1080/01431168008948240

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

ISSN:0143-1161    

DOI:10.1080/01431168008948241

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

ISSN:0143-1161    

DOI:10.1080/01431168008948242

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

ISSN:0143-1161    

DOI:10.1080/01431168008948244

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor