ISSN:0143-1161    

DOI:10.1080/01431168908903982

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

ISSN:0143-1161    

DOI:10.1080/01431168908903983

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The Australian Laser Airborne Depth Sounder (LADS) represents a major technical transition in shallow water hydro-graphic survey that can be compared with the change from the lead line to acoustic sounder. LADS offers a substantially increased rate of data acquisition, a demonstrated accuracy which meets international hydrographic standards and a total area cover capability. The system generates discrete depth measurements in a rectangular grid pattern with 10m spacing between measurements. The concepts, methods and processing algorithms used in the design of LADS are based on an extensive research and development programme which has been widely reported in the technical literature. The LADS system has a depth capability of 50 m with depth errors less than 0.28 m (one standard deviation) over the depth range 2–30 m. LADS, installed in a Fokker F27 aircraft, is designed for operational use with the Royal Australian Navy Hydrographic Service. The project has Department of Defence approval and tenders for the manufacture and commissioning of the system are currently being sought.

ISSN:0143-1161    

DOI:10.1080/01431168908903984

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Simulations of the radiometric signal extracted from optical imagery of shallow water have been performed in order to investigate the systematic and noise-related bathymetric errors which result from spatial variations in environmental parameters. Inversion techniques which utilize only a few selected depth-sounding points as input permitted the study of these errors as a function of operational and environmental parameters. Rather than attempt to incorporate the environmental spatial variations into a single multi-dimensional bathymetric equation, a spatial iteration procedure preceded by a spectral inversion of the radiometric data is used to eliminate the effects of low frequency environmental parameter variation. Additional investigations have been conducted to evaluate the impact of simply neglecting the infinite-depth radiance, a bathymetric equation parameter which is often impractical to measure or whose estimate entails rather serious simplifying assumptions concerning its spatial variation across the image being processed.

ISSN:0143-1161    

DOI:10.1080/01431168908903985

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The action balance equation is solved numerically using the method of characteristics. The algorithm can handle any functional form of the current velocity and the source function. It therefore allows a comparison of the hydrodynamic parts of the models of Alpers and Hennings (1984), Shuchman el al. (1985) and Holliday et al. (1986,1987), all describing the imaging mechanism of mapping bottom topography with side-looking airborne radar (SLAR) and synthetic aperture radar (SAR). The effects of advection and second-order terms, neglected in the original work of Alpers and Hennings (1984), are included and studied. It is shown that advection is important, notably at L-band for features smaller than 1 km, such as sand waves, while the second-order terms shift the modulation of the wave spectrum upward. All models studied give similar results for L-band and X-band, showing that the dependence of the relaxation rate on wave number and wind speed variations due to variations in current velocity has only a small influence. The predicted modulations at L-band are of the order of 10 per cent, in agreement with the Seasat data. At X-band, however, the predicted modulations are an order of magnitude smaller than at L-band. This disagrees with the experimental data which seem to indicate that modulations at X-band are of the same order of magnitude as those at L-band. Advection is important for the positioning of modulations in the radar backscatter relative to the bottom topography. However, the positional accuracy of existing experimental data is not good enough to allow comparison with theoretical predictions.

ISSN:0143-1161    

DOI:10.1080/01431168908903986

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Using Advanced Very High Resolution Radiometer (AVHRR) data for measuring surface temperature can be problematic due to variability in surface emissivity and atmospheric attenuation. Using dates on which the surface was snow covered and the atmospheric attenuation was very low, this paper demonstrates that surface temperature distribution can be accurately mapped using relatively simple microcomputer-based image processing.

ISSN:0143-1161    

DOI:10.1080/01431168908903987

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Though the literature is replete with papers on remote sensing via space satellites, the specifications in terms of jitter and drift rate that have to be met by the specific mission, are often either over-specified or under-specified. In this paper the authors endeavour to present, through heuristic arguments, the effect of jitter and drift on picture quality, and to arrive at the proper specifications on attitude and orbit control systems for remote sensing satellites.

ISSN:0143-1161    

DOI:10.1080/01431168908903988

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Two aspects of spatial degradation of satellite data are examined. The first describes a technique for spatially degrading high-resolution satellite data to produce comparable data sets over a range of coarser resolutions. In this study seven spatial resolution data sets are produced from Landsat Multispectral Scanner (MSS) data resulting in spatial resolutions ranging from 79 m to 4 km applying a spatial filter designed to simulate sensor response. The simulation is demonstrated for part of the Superior National Forest, Minnesota. The second part of the paper examines spatial degradation of coarse resolution data to provide data compression for the production of global-scale data sets. The on-board sampling approach adopted by the National Oceanographic and Atmospheric Administration (NOAA) to produce the Advanced Very High Resolution Radiometer (AVHRR) Global Area Coverage (GAC) data from the 1 km Large Area Coverage (LAC) data, is compared to other sampling procedures. Six sampling procedures were compared for seven terrain types. The GAC sampling procedure provided a relatively poor representation of the 1 km data, particularly for heterogeneous areas. Coefficients of determination for the GAC sampling compared to the original data ranged from 0.49−0.76. Sampling procedures incorporating averaging resulted in a decrease in the variance as compared with the original data. Sampling procedures adopting single-value selection had higher variances and produced data values directly comparable with those from the original data. Sampling scheme design should consider data fidelity requirements as well as the engineering constraints of on-board processing.

ISSN:0143-1161    

DOI:10.1080/01431168908903989

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

This Letter responds to a recent Letter by Hay (1988) which describes a method for correcting interpreted land cover areas based on field survey in the form of a confusion matrix. It is shown how Hay's and an alternative direct method are both stable and sensitive only when there is high contingency between all interpreted and surveyed classes.

ISSN:0143-1161    

DOI:10.1080/01431168908903990

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

This Letter takes the form of a reply to Jupp (1989). It claims that Jupp's alternative direct method of deriving global estimates from confusion matrices is not generally valid, and it comments on some other issues highlighted by Jupp.

ISSN:0143-1161    

DOI:10.1080/01431168908903991

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor