ISSN:0143-1161    

DOI:10.1080/014311697217116

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

This paper reviews the application of remote sensing to the study and control of invertebrate intermediate hosts and vectors for some of the most prevalent of human diseases worldwide. Examples are also taken from studies involving animal diseases that have considerable adverse effects on human welfare. The current status of remote sensing in epidemiology is assessed and suggestions are made on how, in the future, the two fields might be most profitably combined.

ISSN:0143-1161    

DOI:10.1080/014311697217125

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The NOAA/AVHRR derived Normalized Difference Vegetation Index (NDVI) offers immense potential to study dryland ecosystems. Its relation with rainfall in semi-arid regions is both sensitive and complex. The physical basis of this relation is vegetation, mainly grown due to soil moisture availability as the result of the seasonal rainfall, which intercepts photosynthetically active radiation (PAR) and hence directly influences the aggregate of NDVI. While the major part of rainfall is lost through direct evaporation from the soil surface, run-off and drainage, a small fraction of rain water which is used by crops for their growth and yield, is a key parameter linking rainfall with NDVI, especially in dryland tropics. The extent of non-utilized rain water depends not only on the local weather parameters but also on optimal land and water management practices along with the cropping pattern having efficient radiation use efficiencies. Although there have been several studies reporting the relation between AVHRR NDVI and rainfall in semi-arid regions the sensitivity of this relation in varying dryland conditions has rarely been analysed quantitatively. The present study aims to interpret seasonal AVHRR NDVI variations with the seasonal aggregate of rainfall and fraction of soil moisture used by vegetation in the six drought prone districts of Karnataka State, India representing very severe, severe and moderate drought conditions. Area averaged seasonal transpiration which has been theoretically linked to integrated NDVI (INDVI), has been realized up to a certain extent in the study areas. The study reveals a closer AVHRR NDVI relation with the water used by vegetation for its growth and yield than the precipitation in dryland ecosystems.

ISSN:0143-1161    

DOI:10.1080/014311697217134

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

In this paper, an approach for the use of spaceborne SAR data for rice field identification, as well as for land use classification, is demonstrated, by using multitemporal data acquired over the Ohgata-mura area, Akita, Japan with ERS-1 C-band SAR, in 1992. Two techniques for reducing the influence of speckle on the accuracy of rice field identification were tested. A comparison of the SAR results with land use survey data collected in 1993, and with Landsat TM data, shows the potential of the present approach.

ISSN:0143-1161    

DOI:10.1080/014311697217143

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

ERS-1 Synthetic Aperture Radar (SAR) data over a study area located in Papua New Guinea, where there is a high probability of cloud cover, are evaluated on their information content for mapping tropical forest ecosystems. The feasibility of forest/non-forest discrimination using mono- and multi-temporal ERS-1 SAR data at 100m pixel size is investigated using two different classification methodologies. An assessment of the optimal acquisition period and number of acquisitions is undertaken. The automatic classification results are compared quantitatively with the aid of field observations in a comparative accuracy assessment methodology, and a comparison is made with Landsat Thematic Mapper (TM) data. Finally, the potential of ERS-1 SAR data for the discrimination of tropical forest types is investigated. The results showed that multi-temporal ERS-1 SAR data acquired at the appropriate times were found to have a high potential for forest/nonforest discrimination and achieved similar classification accuracies to the TM data. The discrimination of forest types proved difficult. However, discrimination was possible between dense and open forest types having different canopy structures.

ISSN:0143-1161    

DOI:10.1080/014311697217152

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Upwelling radiance from savanna woodlands may originate from two separate layers: (1) the field layer, which is a mixture of soil, litter and herbs, and (2) the tree layer composed of woody parts and leaves. Unless detailed field data are available for a particular savanna location, it is unknown how the individual layers may influence the red and near-infrared signals and whether radiative interactions between layers are important. We employed an existing radiative transfer model (SAIL) in conjunction with a simple, single-scattering model to analyse the variation in Advanced Very High Resolution Radiometer (AVHRR) channel 1 and 2 response as well as NDVI for savanna-woodland vegetation in eastern Zambia. Linear fits between predicted and observed values of reflectance and NDVI were significant ( p 0.05) in the red and in NDVI, however, the model failed to explain a high proportion of the variation in near-infrared. Red and NDVI in sites where tree cover was high were also poorly modelled, which suggests that multiple interactions between canopy layers make a single-scattering model unreliable, particularly in the near-infrared. Modelled results were also compared to aircraft radiometer measurements provided by the integrated camera and radiometer instrument (ICAR). Simulations parameterized with field data suggest that the model may be used to infer tree and field layer influences at different points during the seasonal cycle. Results also suggest that the field layer dominated the signal in our savanna woodland sites throughout most points of the seasonal cycle, which is consistent with other canopy radiative-transfer studies. Simulations indicated that the tree layer was a relatively more important component of NDVI during the dry season when the field layer was largely senescent, accounting for 20-40 per cent of the satellite signal.

ISSN:0143-1161    

DOI:10.1080/014311697217161

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

To aid in the environmental planning and management of Los Haitises National Park, a neotropical park in the Dominican Republic, a land cover change analysis was performed on the lower Yuna River watershed, within which a portion of the park exists and which contains a diversity of agricultural practices. Separate image classifications were performed on a 1973 Landsat MSS image and a 1985 Landsat TM image with resulting overall classification accuracies of 77.3 per cent and 81.3 per cent, respectively. In both classifications, spectral similarities between the various growth stages of rice, mangrove, orchard, and permanent grassland made separation and delineation of these classes difficult. The implications of land cover trends within the watershed for ecologic and economic management issues which affect both the watershed and the park were discussed.

ISSN:0143-1161    

DOI:10.1080/014311697217170

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The smallfield pattern characteristic of the Northern Ireland landscape necessitates the use of high resolution remotely-sensed imagery in grassland studies. In August 1986, 5 m resolution ATM and 30 m resolution TM data was collected from a grassland area in Northern Ireland. Herbage mass, sward surface height and botanical characteristics were assessed for approximately 120 fields in the overfly area. Correlations between digital numbers (DN) in three wavebands for both resolutions from commonly sampled fields were poor as a result of small field size and poor overlap of pixel area sampled. Variability and error associated with ground data probably masked any effect of small field size. Height, mass and percentage dead matter were the sward variables predicted with most accuracy by DN but most correlations were low and 5 m resolution was better than 30 m resolution. Both sets of imagery appear to have more potential to improve and quantify grassland classifications rather than provide absolute values for useful sward parameters.

ISSN:0143-1161    

DOI:10.1080/014311697217189

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

An advance thermal video radiometer (TVR) was mounted onboard a helicopter and used to collect data over Tel-Aviv, Israel, from an altitude of 7000 feet. The sensor, sensitive to the 3-12 mu m spectral region, consisted of an onboard calibration device and a 1.8 mRad instantaneous field of view (IFOV), which enabled direct assessment of surface radiometric temperature patterns in very high spatial and thermal resolutions. The TVR capability was examined by studying the microscale structures of the urban heat island (UHI) of Tel-Aviv, Israel, during a stable calm night on 28 February 1995. The TVR data were found to be of high quality in terms of signal to noise ratio, reproducibility, stability, thermal sensitivity and spatial resolution capabilities. The radiometric data were analysed against air temperature acquired during the flight time by four mobile traverses that crossed the city from north to south. A significant heat island was identified over the inner city areas, which was found to be 5 C warmer than the rural areas located 4 km to the south-east. Throughout the city, asphalt was found to be the major heat source whereas vegetation was found to be the most cooling element. A linear regression analysis between the air and radiometric temperatures showed that in general, good agreement exists between the two temperatures. Along the western routes (A and B) the correlation was relatively higher than that along the eastern routes (C and D) and was significantly different in the linear regression slope a . We assume that differences in atmospheric conditions, especially in the water vapour variation throughout the city, caused these inconsistencies. We concluded that the examined TVR is a very promising, low-cost remote sensing sensor, which can rapidly and quantitatively monitor the UHI in very high spatial and thermal resolutions from a high altitude. Based on these results we strongly recommend that the TVR be further examined in other remote sensing applications.

ISSN:0143-1161    

DOI:10.1080/014311697217198

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Mapping of remotely-sensed data to a common projection can potentially degrade the quality of the data. The Canada Centre for Remote Sensing (CCRS) has developed the Geocoding and Compositing System (GEOCOMP) to map Advanced Very High Resolution Radiometer (AVHRR) data to a 1 km2 equal area projection. Using data from the Boreal Ecosystem-Atmosphere Study (BOREAS), we tested GEOCOMP's processing of individual pixels and its ability to preserve the spatial integrity of the original AVHRR observations. Our study shows that GEOCOMP processing does not significantly degrade the ability to derive environmental variables and indices using a contextual approach. Errors produced by the GEOCOMP system are largest for scenes with high radiometric contrast and the parts of scenes with large satellite view angles.

ISSN:0143-1161    

DOI:10.1080/014311697217206

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor