ISSN:0143-1161    

DOI:10.1080/014311697216540

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The paper presents a method and results of stereo extraction of planimetric and altimetric features from digital airborne SAR data on a low cost PC based stereo-workstation (DVP). A challenging study area was chosen in a mountainous area of Costa Rica. Accuracies of 24 m, 39 m and 40m have been achieved for roads, creeks and digital elevation models respectively. Better contrasts in the feature definition is a key point to improve planimetric positioning accuracies. If roads and creeks accuracies are almost independent of the location in the stereo-model, larger intersection angles enable a better digital elevation model accuracy (around 20 per cent). Surprisingly, the type of the relief does not affect the results, except for very shallow angles. The multiple stereo capability of RADARSAT will be a valuable source to ensure precise results of this research.

ISSN:0143-1161    

DOI:10.1080/014311697216559

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

During the joint U.K./U.S.A. experiment conducted in the Loch Linnhe, Scotland, U.K., in 1989, the Jet Propulsion Laboratory (JPL) multifrequency airborne synthetic aperture radar (SAR) was deployed to investigate the relation between the SAR images and ship-generated internal waves. One of the intriguing results, consistent throughout the experiment, was the striking difference in phase (position) between the images of internal wave wakes in the P-band ( 68cm) wavelength and those in L-band ( 24 cm) and C-band ( 6 cm) wavelengths. An explanation for this difference is found in the sensitivity of different radar wavelengths to oceanic surface waves in different ranges of wavelengths, that are perturbed by varying surface currents by different amounts and at different positions, depending on the wavelength of surface waves.

ISSN:0143-1161    

DOI:10.1080/014311697216568

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The relative effectiveness of Landsat Thematic Mapper (TM) and SPOT multi-spectral data were compared for mapping shrub and meadow vegetation in northern California. Shrub vegetation included evergreen chaparral and deciduous willows and alders. Meadow vegetation included grass-dominated meadows on wet soils and forb-dominated meadows on drier sites. Despite differences in growth forms and species compositions, there was considerable similarity in spectral signatures among vegetation types. Because of greater spectral resolution, TM data were more effective than SPOT data in separating shrubs from meadows, but neither TM nor SPOT data were effective at separating meadow types.

ISSN:0143-1161    

DOI:10.1080/014311697216577

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

In this study, we attempted to determine surface temperature with a split window algorithm accounting for differential absorption effects of the Earth's atmosphere. We studied the dynamic response of surface temperature, over an extensive wheat-growing tract of India during different phenological stages of the crop, in relation to the normalized difference vegetation index (NDVI). Good agreement was obtained between the exponentially fitted surface temperatures recorded at the meteorological observatories, and the satellite-retrieved temperatures. We also observed a strong negative dynamic correlation between the NDVI and the retrieved surface temperature. We analysed the results on the basis of the phenology of the wheat crop, the land area under agriculture, and vegetation. Our study has indicated the utility of NDVI as a modulating parameter for the estimation of surface temperature.

ISSN:0143-1161    

DOI:10.1080/014311697216586

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Scalar conversion of raw NOAA AVHRR Normalized Difference Vegetation Index (NDVI) values into Digital Numbers (DN) is commonly used for graphic display purposes. Retention of these DN values for calculation of pixel level NDVI parameters results in incorrect values for the pixel level Coefficient of Variation (CoV)

ISSN:0143-1161    

DOI:10.1080/014311697216595

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Use of Digital Number (DN) representation of Normalized Difference Vegetation Index (NDVI) values for calculation of the Coefficient of Variation (CoV) of NDVI produces incorrect results. We show how CoV images correctly calculated directly from NDVI values differ from images incorrectly calculated through the use of DNs, and explore the ways in which the legitimate calculation of CoV allows us to revise and refine our perceptions of what we mean by the term 'Sahel'.

ISSN:0143-1161    

DOI:10.1080/014311697216603

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The primary objective of this research is to develop a surface albedo model for the National Oceanic and Atmospheric Administration (NOAA) Advanced Very High Resolution Radiometer (AVHRR). The primary test site is the Konza prairie, Kansas (U.S.A.), used by the International Satellite Land Surface Climatology Project (ISLSCP) in the First ISLSCP Field Experiment (FIFE). In this research, high spectral resolution field spectrometer data was analyzed to simulate AVHRR wavebands and to derive surface albedos. Development of a surface albedo algorithm was completed by analysing a combination of satellite, field spectrometer, and ancillary data. Estimated albedos from the field spectrometer data were compared to reference albedos derived using pyranometer data. Variations from surface anisotropy of reflected solar radiation were found to be the most significant albedo-related error. Additional error or sensitivity came from estimation of a shortwave mid-IR reflectance (1.3-4.0 mu m) using the AVHRR red and near-IR bands. Errors caused by the use of AVHRR spectral reflectance to estimate both a total visible (0.4-0.7 mu m) and near-IR (0.7-1.3 mu m) reflectance were small. The solar spectral integration, using the derived ultraviolet, visible, near-IR and SW mid-IR reflectivities, was not sensitive to many clear-sky changes in atmospheric properties and illumination conditions.

ISSN:0143-1161    

DOI:10.1080/014311697216612

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Estimation of contemporary production regions of major cereal around the world is significant to predict food supply in the 21st century. We introduced the concept of suitable regions for cultivation. Our proposed method is to identify global suitable regions for major cereal cultivation using weather data, soil data, and vegetative biomass change patterns. We estimated the present area of suitable regions for major cereal cultivation to be 515 Mha. By comparison with the 1993 FAO statistical values, it was concluded that our method accurately identifies global suitable regions for major cereal cultivation and determines their area. Under conditions of double the current CO2 concentration, it was estimated that the area of suitable regions would be 279 Mha which represents a decrease of 46 per cent.

ISSN:0143-1161    

DOI:10.1080/014311697216621

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The Scottish Office's Land Cover of Scotland 1988 Survey (LCS88), was announced in May 1987 and was intended to provide the first-ever detailed census of land cover in Scotland. It came about as a result of increasing concern about the nature and rate of land use change in rural Scotland and the need to obtain objective baseline information on which to build and evaluate future countryside policy. One of the recommendations of a Scottish Office feasibility study carried out prior to the LCS88 survey, was that satellite remotely-sensed data should be considered for measuring landscape change in the future. This paper relates specifically to this recommendation and presents the results of an evaluation study to investigate the use of limited acquisition satellite imagery from Landsat Thematic Mapper, to derive a land cover classification and spectral segmentation information to enhance the existing LCS88 dataset. Although a successful land cover, primary as well as some individual cover features, was obtained from the satellite data, the overall accuracy comparison with the LCS88 cover features was limited. However, the opportunistic mapping of important agricultural crops and primary cover types, such as oilseed rape and forestry cover features, or the interpretation of some of the considerable confusion between semi-natural grassland and improved grassland cover features, provided for an enhanced LCS88 dataset. This was also true for the illustration of the considerable potential of a satellite classification and spectral data, for identifying the component parts of LCS88 Mosaic cover features and estimating vegetation quality.

ISSN:0143-1161    

DOI:10.1080/014311697216630

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor