ISSN:0143-1161    

DOI:10.1080/01431169508954389

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Azimuthally travelling ocean waves are seldom well imaged by microwave real aperture radar (RAR) operating with conventional HH or VV polarizations. Attenuation of image intensity modulation in the azimuthal direction implies that ocean wave spectra derived from such images also will not be accurate. Real aperture radar cross-section modulation by long ocean waves is normally attributed to two principal sources, tilt modulation and hydrodynamic modulation. In ocean radar images both of these modulation sources are significantly attenuated in the azimuthal direction. Therefore, complete two-dimensionalk-space wave spectra derived from microwave data often are quite different than physical ocean spectra. This paper uses fully-polarimetric radar measurements of ocean backscatter to identify a new source of backscatter modulation that is strongest in the azimuthal direction. This modulation source has potential for augmenting tilt and hydrodynamic modulation sources in the azimuthal direction where their weakness causes poor wave visibility. The predicted improvement in the measurement of ocean wave spectra using an optimized polarization is investigated by means of aRARocean imaging model. Fully-polarimetric, and conventional, radar spectrometers are proposed which are specifically optimized to sense wave-tilts in the azimuthal direction.

ISSN:0143-1161    

DOI:10.1080/01431169508954390

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The French frequency modulated continuous waves (FMCW) scatterometer ERASME mounted on small helicopter or aircraft has been designed as dualfrequency (CandXbands) and dualpolarization (HH, VV) to investigate simultaneously the vegetation and the soil responses in radar backscattering. It is operated as a forward looking radar with a large elevation beamwidth (± 10° at 3 db) to observe easily the same surface target over a large range of incidence angles during a single flight. By this ability, ERASME is a complementary research tool for intercalibration of airborne and spaceborne imaging Synthetic Aperture Radars like Radarsat and ASAR and has to be well calibrated in every configuration, both absolutely and relatively for comparisons at different incidence angles.

ISSN:0143-1161    

DOI:10.1080/01431169508954391

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

By using a sea surface temperature profiler buoy, the behaviour of the vertical temperature profile near the sea surface was observed in Mutsu Bay. In the daytime under calm and strong sunshine condition, there occurred a large temperature difference between the uppermost sea surface and the 1 m depth. The difference disappeared when the wind began to blow with a speed greater than 4ms−1. Besides the atmospheric effects the inhomogeneity of the vertical temperature distribution near the sea surface must be another major error factor in the sea surface temperature estimation by satellite remote sensing.

ISSN:0143-1161    

DOI:10.1080/01431169508954392

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Sea-surface temperatures (SST), as observed from a space-borne radiometer (AVHRR), are related to surface currents as measured by the high-frequency coastal radar (CODAR) in Norwegian coastal waters. Both systems yield about the same spatial resolution of the order of 1 km. Introducing a number of simplifying assumptions, the geostrophic portion of surface currents is derived from the SST distribution and compared with the CODAR measurements. In areas, characterised by strong temperature gradients, good agreement is found for current velocity and also for relative vorticity.

ISSN:0143-1161    

DOI:10.1080/01431169508954393

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

A simple theory is developed relating Secchi disc depth to reflectivity, just below the surface, in the green band. The theory contains one adjustable constant, B, the ratio of backscattering to total scattering coefficients for suspended particles. A method is then outlined for correcting the satellite data for atmospheric effects. Secchi depths are then compared with reflectivities, in the green, in two Landsat Multi-spectral Scanner (MSS) scenes. It is found that for Secchi depths< 16m, the theory provides a good fit to the data with B = 0.0077.

ISSN:0143-1161    

DOI:10.1080/01431169508954394

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

We present an orbit/scan/geolocation model for systems based on a rotating mirror—such as the Along Track Scanning Radiometer (ATSR) and the Advanced Very High Resolution Radiometer (AVHRR). For ATSR-2, we show how the Bi-directional Reflectance Distribution Function (BRDF) is sampled at different latitudes and times of year. We calculate the shape and weighting functions of the ground resolution elements and the local sampling behaviour. We conclude that, for strongly heterogeneous scenes, a simple map of the nadir data onto the forward data may not suffice. We discuss two of the possible telemetry schemes proposed for ATSR-2. In one there is lower spatial resolution. In the other the swath width is reduced and the inter-visit time increased.

ISSN:0143-1161    

DOI:10.1080/01431169508954395

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Prior knowledge of class occurrence can be used in conventional statistical classifications to increase classification accuracy significantly. These classifications, however, require typically a large training set for their correct use. When small training sets are available therefore an alternative classification technique is required and one increasingly popular alternative is the use of artificial neural network techniques. Whilst many comparative studies have shown artificial neural network classifications to be more accurate than those derived from conventional statistical classifiers the difference in accuracy can be more than made-up if prior knowledge was incorporated in the statistical classification. To make the full use of artificial neural networks therefore approaches for the incorporation of prior knowledge must be developed. This paper proposes one approach which may be used and illustrates its use in the classification of agricultural crops from synthetic aperture radar data with a minimal training set. The results show that whilst the artificial neural network could accurately learn the training data the classification of an independent testing set was poor, an accuracy of only 27.0 per cent was derived for a seven class classification. Incorporating prior knowledge, however, significantly increased classification accuracy to 58.4 per cent. This latter result was comparable, in terms of accuracy and the pattern of class allocation, to a classification of the same data set by a discrimination analysis with prior knowledge.

ISSN:0143-1161    

DOI:10.1080/01431169508954396

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The classification of multiband remote sensing data may require a huge amount of computer time. In the present paper, we discuss a fast maximum likelihood classifier based on the concepts of thresholding, partial sum logic, Winograd's inequality and a linear algebraic theorem. The performance of this classifier has been tested using four sets of remotely-sensed data. The results have been discussed and compared with the original maximum likelihood classifier.

ISSN:0143-1161    

DOI:10.1080/01431169508954397

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Remote sensing technique by satellite has been well-developed in recent years. In this paper two kinds of statistical correction methods are proposed to clarify observation data by NOAA with atmospheric scattering. The first method is the deletion of the path radiance effect by the least squares method. The second uses a smoothing filter. These methods are applied to the original remote sensing data collected on 26 July 1987.

ISSN:0143-1161    

DOI:10.1080/01431169508954398

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor