ISSN:0143-1161    

DOI:10.1080/01431169008955027

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The split window method is successfully being used to retrieve the temperature over sea surfaces from satellite radiances in clear sky and has the great advantage of simplicity. However, such a method does not work over land surfaces, mainly because the emissivity is not equal to 1 and depends on the channel. An extension of this method to apply to land surfaces requires one to take account of emissivity—such an extension is presented in this paper. First, using Lowtran 6, the accuracies of the various linearizations of the radiative transfer equation leading to the split window are checked. This implies that the retrieved surface temperature depends linearly on emissivities and brightness temperatures. Such behaviour has been checked on actual examples. Theoretical equations are then derived which show that the actual surface temperature can again be expressed as a linear combination of the brightness temperatures measured in two adjacent channels with coefficients depending on spectral emissivities but not on atmospheric conditions. Using Lowtran 6 these properties have been verified and the dependence of these coefficients has been explicitly computed leading to a local split window method for the NOAA-9 Advanced Very High Resolution Radiometer. Finally, we show that accurate surface temperatures can be retrieved using this local split window method once emissivities in two adjacent channels are known with sufficient accuracy.

ISSN:0143-1161    

DOI:10.1080/01431169008955028

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

An effort has been made to retrieve surface spectral reflectance from satellite radiance measurements. For this purpose, a simple cubic equation with surface reflectance as one of its roots has been derived. Besides satellite measured radiance, the other required quantities in the equation are calculated by using the actual solution of radiative transfer equation by a discrete ordinate method, taking into account the inhomogeneous aerosol distribution. The method has been tested for internal consistency by numerical simulations using realistic aerosol profiles. Finally, it has been tested with a Landsat image, giving good agreement with ground observations.

ISSN:0143-1161    

DOI:10.1080/01431169008955029

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Thermometric observations over a row crop (cotton, Gossypium hirsutum L.) with 20 per cent cover using hand-held radiometers were made during several clear days near Maricopa, a town in south central Arizona. A ground sampling routine developed for estimating a composite temperature for the cotton field compared favourably with surface temperatures taken for one day from an aircraft flying at an altitude of approximately 150 m. Both ground and airborne radiometric measurements were from nadir angle traversing the row crop. It was found that by considering an equation for the radiative balance at the surface, a composite surface temperature could be calculated which was within ± 1.5°C of the value given by the labour-intensive ground sampling method or the aircraft. The data requirements were temperatures of sunlit and shaded soil and the sunlit canopy temperature and their respective fractional areas. The fractional areas of the sunlit and shaded soil as a function of time and the vegetative cover were estimated with extensive agronomic measurements and nadir photographs. A model similar to that of Kimes (1983) requiring only information on row orientation and the height and width of the vegetation produced estimates of the fractional areas close to the labour-intensive ground measurements. Therefore, it is possible to obtain estimates of the composite surface temperature comparable to low-flying aircraft observations over row crops with sparse cover without having to devise a labour-intensive ground-sampling routine and extensive agronomic measurements and photographs to determine fractional areas of the composite scene. However, there is some uncertainty as to the number of thermometric observations needed to obtain reliable estimates of sunlit and shaded soil and sunlit canopy temperatures.

ISSN:0143-1161    

DOI:10.1080/01431169008955030

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Spectral classes resulting from an unsupervised maximum-likelihood classification of Landsat Thematic Mapper imagery are found to provide the basis for a thematic map of broad habitat types over an area of complex semi-natural vegetation. Contingency tables are used to assign spectral classes to cover types, in addition to calculating classification accuracy. Detailed cover categories identified on the basis of ecological divisions are poorly represented by the spectral classes, but broader cover categories chosen such that they have some spectral homogeneity, in addition to ecological significance, show good agreement. Photographic prints of the satellite imagery were found to be of value both for determining and for mapping cover categories in the field.

ISSN:0143-1161    

DOI:10.1080/01431169008955031

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The experimental reflectance data of Hueteet al. (1985) for field-grown cotton, beneath whose canopy soils differing widely in brightness had been inserted, were applied to two composite-scene reflectance models. In the additive-independent reflectance model (AIRM), the Sunlit soil, shadowed soil and Sunlit vegetation responses are considered as independent signals that are added linearly in porportion to the fractional ground area each component occupies. The transmittance-reflectance interactive model (TRIM) developed herein considers the reflectance of transmitted light up through the canopy from the soil as well as that reflected from the canopy itself. The TRIM model simulated the experimental measurements satisfactorily over the 0–100 per cent plant cover range for all soil backgrounds, whereas the AIRM model did not. The greenness lines closely paralleled the soil line for the AIRM model and thereby deviate from the measured lines at all plant covers. The greenness line slopes increased as the plant cover increased in the TRIM in agreement with experimental observations. The larger the proportion of shadows in the composite scene, the more important the reflectance-transmittance terms were in the TRIM. These results support other evidence that plant, soil and shadow reflectance components mix interactively to produce composite canopy reflectance.

ISSN:0143-1161    

DOI:10.1080/01431169008955032

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

This paper deals with the most important Swedish agriculture crops in relation to (i) Landsat-based spectral differences, (ii) mono- and multi-temporal Landsat classification measured as producer's, user's and Kappa accuracy and (iii) Landsat classification determined as area estimation accuracy. The potential of satellite data for crop monitoring in Sweden was found to be rather low for most crops except rape seed and sugar beet. Concerning these crops results indicated a possible operational applicability.

ISSN:0143-1161    

DOI:10.1080/01431169008955033

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Information on the spatial distribution of different wasteland categories forms a basic component in the large-scale reclamation and utilization programmes of these degraded lands. To evaluate the use of Landsat Thematic Mapper (TM) data in wasteland mapping, an attempt was made in this study to delineate and map various kinds of wastelands, in parts of Aligarh District (Uttar Pradesh) by digital analysis of Landsat TM data of 27 January 1986, using the maximum-likelihood classifier method. Map-to-image rectification of the sub-image and a selection of suitable spectral bands based on spectral response and training statistics, were also performed before the final supervised classification. The results indicated that, out of the six TM bands (excluding the thermal band), the spectral separability of all wasteland categories are most possible in bands 3, 4, 5and 7. This study also reveals that wasteland types, namely salt-affected and surface waterlogged/marshy lands could be effectively delineated, mapped and digitally classified with an accuracy of about 96 per cent, using spatially and spectrally improved Landsat TM data.

ISSN:0143-1161    

DOI:10.1080/01431169008955034

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

In situ and Landsat Thematic Mapper (TM)-derived reflectances of the Forbindels Glacier, Greenland, were acquired in August of 1986. Reflectance was measured in situ using a portable spectrometer and calculated using TM data and ancillary information. Atmospheric corrections were applied to the at-satellite reflectances resulting in a 5-17 per cent increase in reflectance relative to the calculated at-satellite reflectances. The satellite-derived, corrected reflectances obtained from the non-saturated TM bands corresponded to within 6 per cent of the in situ reflectances measured at the nadir viewing angle with a portable spectrometer. Measurement of nadir reflectances using Landsat-TM data appears to be a viable method to obtain physically meaningful reflectances of ice and snow.

ISSN:0143-1161    

DOI:10.1080/01431169008955035

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The value of utilizing multiple data sources for classifying images has long been recognized in remote sensing. However, any attempts to do so have faced enormous problems primarily due to the inadequacy of traditional single source analytical techniques. This paper demonstrates the feasability of using knowledge-based procedures to provide a new scheme for incorporating several sources in the classification process. The two schemes presented (based on numerical and qualitative reasoning) are computationally efficient and have high classification accuracies.

ISSN:0143-1161    

DOI:10.1080/01431169008955036

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor