摘要:

An important system-performance parameter for remote-sensing systems is the spatial resolution. This term has an imprecise meaning and there are a multitude of different definitions. In this paper, the most important definitions are reviewed and consideration is given to the factors which influence the resolution of a given system. It is concluded that no single definition of spatial resolution can be applied to all systems, nor can spatial resolution alone be used to measure the significant information content of image data.

ISSN:0143-1161    

DOI:10.1080/01431168308948568

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

A composite image† of the United Kingdom has been constructed from 43 Landsat scenes by a wholly digital procedure, using a Prime 750 computer. The scenes were first transformed to National Grid coordinates, using 1200 ground control points, the resampling giving 100 m square pixels.

ISSN:0143-1161    

DOI:10.1080/01431168308948569

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

The Indian subcontinent is the region lying between about 60 and 100°E longitudes and the equator and 40°N latitudes. About one-quarter of the world's population live in this region, with an average population density of about 400 persons per square mile. This region has a belt of fold mountains, including the highest, the Himalayas, a chain of islands, large desert areas, evergreen tropical forests and low-lying plains fed by perennial rivers. It has every type of climate, soil and vegetation ranging from frozen tundra to dense rain forests. The region is endowed with natural resources, but is, however, economically poor and deficient in food and usable fresh water. The immediate problems are timely assessment of crops and their conditions such as drought, the spread of pests and diseases which if detected and remedied in time would result in the saving of crops. The desert areas also need continuous observation to help derive effective methods of arresting the spread of deserts. Because of the presence of perennial rivers there is good potential for having major irrigation and hydroelectric power projects, and studies over vast command and catchment areas are necessary. Floods in these rivers pose a big problem and flood plain mapping is of utmost importance. Forest wealth has been dwindling fast and proper assessment of present day land use and encroachment on forest land has to be detected and checked. Thus remote sensing has a great potential as an important tool for providing a mass of data which could then be used for solving the problems of backwardness of this region. These problems of the Indian subcontinent and how remote sensing can help is discussed in detail.

ISSN:0143-1161    

DOI:10.1080/01431168308948570

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Ground data requirements are more stringent and difficult in aerial water quality surveys than in land surveys, as a result of the dynamic nature of water quality as well as the complex energy-water interaction giving rise to noise components in the signal measured by the airborne sensor. This paper presents some of the considerations influencing the ground truth strategy adopted in recent NRSA (National Remote Sensing Agency) water quality studies. Various aspects such as depth of sampling, time-lags, location of sampling sites on remotely sensed data, elimination of spectral noise components and planning of redundancy in ground truth are addressed. Careful collection, preservation, storage and analysis of water samples can contribute significantly to reliable water quality mapping from aerial altitudes.

ISSN:0143-1161    

DOI:10.1080/01431168308948571

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

More than one-third of the total irrigated croplands in Tamil Nadu State in India are under tanks which are man-made water impoundments. The data base regarding availability and agricultural use of this resource is, however, inadequate and outdated. This paper presents an evaluation of the feasibilityof using satellite sensing techniques to generate current information and periodically to update the tank irrigation data. Tanks can be mapped reliably from satellite altitudes. Regional regression models can be developed in which waterspread areas measured on satellite data can be input to provide estimates of the volume of water stored in the tanks. Suitable single-date or, if necessary, multidate LANDSAT data may be used to map croplands irrigated by tanks and manual inventory methods may be employed to estimate the cropland acreage. In view of the frequent cloud cover conditions, a methodology needs to be developed in which LANDSAT data and aerial photography may be combined cost effectively with ground surveys to provide baseline information on tank irrigated areas and to update the data base periodically.

ISSN:0143-1161    

DOI:10.1080/01431168308948572

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Unlike framed or photographic data, data of the types represented by the Landsat MSS and thematic mapper are of such a nature that each picture element or small group of elements is acquired at a different time within and among spectral bands and, within a sampling sequence, there is no simultaneity of time or site among bands. This paper explains these time-space relationships by depicting and describing how the data are acquired.

ISSN:0143-1161    

DOI:10.1080/01431168308948573

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Parts of two multispectral Landsat scenes, compressed by ratio 6·4/1, were investigated on the effect of the compression on the image contents. Landsat images of the Bayuda desert in Sudan and the Baltic Sea have been submitted to supervised maximum likelihood classification. Partitioning of classified images is given on a percentage basis as a function of sigma. Three-dimensional clusters of spectral channels and histograms show the influence of compression. Discussion of results shows effect of compression on partitioning of classified scenes, being displayed in several tables and figures.

ISSN:0143-1161    

DOI:10.1080/01431168308948574

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Effects of cross radiance, i.e. of reflection from one area and scattering to the zenith over another area (the object pixel) with a different reflectivity, are computed and presented as point-spread functions. The analysis concerns imaging a planar terrain with Lambert law reflectivity, when viewed from the zenith through an optically and geometrically thin horizontal layer of scatterers. The Henyey-Greenstein phase function, with various values of the anisotropy factor g, is assumed for the scatterers. The characteristics of the point-spread functions depend markedly on the value of this anisotropy factor. Based on this analysis, spatial (surface) resolution, when effectively limited by the atmospheric cross radiance, is defined and computed.

ISSN:0143-1161    

DOI:10.1080/01431168308948575

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Surface reflectance and global irradiance variations across an imaged area determine the minimum signal difference from groups of pixels in different targets needed to discriminate them. The factors affecting such variations and their magnitudes are considered in this paper. The sensor output also depends upon the interaction of the spectral response of the sensor and the spectral upwelling radiance from the target. From a consideration of the spectral instrument responses of detectors in the Landsat multispectral scanners (MS), together with measured reflectance factors of a vegetative canopy stressed to different levels of severity, the feasibility of mapping and quantifying disease stress with Landsat vegetative indices (VINs) is demonstrated.

ISSN:0143-1161    

DOI:10.1080/01431168308948576

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

We have measured the fluxes of mass and latent heat in summer thunderstorms over Europe by using Meteosat images lo measure the rates of expansion of the cirrus anvils. These measurements are compared with previous satellite estimates of thunderstorm fluxes in both mid-latitudes and the tropics, and also estimates made using other techniques. Four of the storms had mass fluxes in excess of 109kgs−1, which is large for a mid-latitude thunderstorm and comparable with a large tropical thunderstorm.

ISSN:0143-1161    

DOI:10.1080/01431168308948577

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor