ISSN:0143-1161    

DOI:10.1080/01431169608949153

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

While considerable effort has been expended on research into the analysis of optically thin cirrus clouds, the global detection and accurate identification of these clouds remains inadequate, especially in daytime meteorological satellite imagery collected over land surfaces. Recently, 1·38 μm imagery was recommended for the improved detection of these thin cirrus clouds. Since this channel is centred on a strong water vapour absorption band and water vapour is concentrated in the lower atmosphere, incident solar energy in the 1·38 μm spectral band is strongly attenuated once prior to reaching the Earth's surface and a second time after being reflected back toward space under normal atmospheric conditions. Thus, it has been postulated that any energy measured by an airborne (or space-borne) radiometer operating in this spectral band would originate from scattering off of mid-level water and high-level ice clouds, making even thin cirrus readily detectable. While initial results have been encouraging, more quantitative analyses are needed to assess the value of 1·38 μm imagery as a candidate for the next generation of polar-orbiting meteorological satellites. Thus, this project investigates the potential for improved thin cirrus detection in daytime imagery collected over land surfaces using scenes of nearly coincident Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) sensor data, which collects 1·38 μm imagery, and Advanced Very High Resolution Radiometer (AVHRR) imagery collected by National Oceanic and Atmospheric Administration (NOAA) operational meteorological satellites. Results show that the addition of 1·38 μm imagery significantly improves the detection of optically thin cirrus clouds in these daytime data. However, the 1·38 μm imagery does not mask all energy reflected by all surfaces as suggested previously. Thus, the accurate use of 1·38 μm data in an automated cloud classification algorithm requires the development of a detection threshold that varies with surface albedo in the 1·38 μm band and atmospheric water vapour concentration. Meanwhile, it is concluded that imagery collected in the 1·38 μm band significantly improves the detection of optically thin cirrus clouds in daytime imagery collected over land surfaces and would be a valuable addition to future meteorological satellite sensors.

ISSN:0143-1161    

DOI:10.1080/01431169608949154

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Imagery from Russian Cosmos series near-polar orbiting satellites has recently become more widely available. We have obtained KATE-200 photographic imagery of ice caps in the European high Arctic archipelagos of Franz Josef Land and Svalbard, and from the Greenland Ice Sheet. This visible-band imagery is of high spatial resolution (nominal 15 m) and each image covers a large ground segment (approximately 59 000km2). KATE-200 products are first generation film positives, first generation film negatives, and prints. No calibration standards or grey scales are provided. A number of ice-surface topographic features can be extracted from these high resolution photographic products. Examples include flow directions in the Greenland Ice Sheet and drainage-basin ice divides on Svalbard ice caps. The large area covered by each KATE-200 image, almost twice that of a Landsat scene, and over 15 times that of SPOT, is an advantage when monitoring the occurrence of glacier surges. The 15 m resolution clearly distinguishes heavy crevassing which affects the ice surface during surging. The combination of large format (a nominal 243 km × 243 km, but in fact up to at least 333 km × 333 km in some launches) and high spatial resolution also makes KATE-200 imagery very suitable for monitoring changing snowline position at both intra- and inter-annual timescales. The occurrence and size-frequency distribution of icebergs can also be measured, and bergs up to 2·3 km in length have been observed in Russian Franz Josef Land.

ISSN:0143-1161    

DOI:10.1080/01431169608949155

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A multispectral classification algorithm is developed for classifying remotely-sensed data extracted from parcels in an agricultural region. The developed multispectral classification algorithm is based on the comparison of the probability density function of the mixture of three normal distributions constructed for a test parcel (test class) with the probability density functions of the mixture of three normal distributions constructed for control parcels (control or information classes) one by one according to the distances between them. A discriminant function is defined and a decision rule is established for the developed multispectral classification algorithm. The discriminant functions for the developed multispectral classification algorithm take values between 0 and 2, end points are included. The discriminant function values give extra information which can be used in decisions about the comparisons in the developed multispectral classification algorithm. The extra information includes similarity and difference percentages or degrees in the comparisons of a test parcel (test class) with control parcels (control or information classes). This makes the classification results more clear and could help researchers better interpret the classification results of the remotely-sensed data.

ISSN:0143-1161    

DOI:10.1080/01431169608949156

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Spectral mixture modelling has developed in recent years as a suitable remote sensing tool for analysing the biophysical and compositional character of ground surfaces. In this paper the potentiality of the linear spectral mixture model to extract vegetation related parameters from 0·4-2·5 μm reflectance data has been tested. High spectral resolution reflectance measurements of soil-plant mixtures with different soil colour and plant densities were carried out in a laboratory experiment. The constrained least-squares and the factor analysis unmixing procedures were applied to generate endmember fractions of the components present in the mixtures and to test the validity of the model. It is concluded that the derived fraction of the vegetation endmember is less sensitive to soil background than the NDV[. The accuracy attainable by this modelling approach can be considered sufficient for many practical purposes, being operational in the monitoring of vegetation from satellite data.

ISSN:0143-1161    

DOI:10.1080/01431169608949157

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

This paper presents the results of field testing a radar model which relates leaf area index to radar backscatter for ERS-1 C-band VV polarization SAR data. Ground truth measurements of leaf area index and soil moisture content were made in selected sugar beet fields, with simultaneous acquisition of ERS-1 SAR image data. Radar backscatter coefficients were derived from the calibrated ERS-1 SAR data. The Leeuwen and Clevers expression of the water cloud model was fitted to determine the insiturelationship between radar back-scatter and leaf area index. The model can be inverted analytically to calculate leaf area index from radar backscatter. The results show considerable potential for the operational application of ERS-1 SAR data in crop monitoring.

ISSN:0143-1161    

DOI:10.1080/01431169608949158

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

A two-stream description of the interaction of radiation with vegetation and an underlying surface is applied to experimental data from a sugar-beet canopy. The two parameters of the theory (reflectance of a dense canopy, and the attenuation coefficient for radiation in the canopy) are determined for chlorotic and normal sugar-beets, thereby allowing estimation of leaf area index from remotely-sensed reflectance measurements. Comparison with previous results for corn suggest that the parameters are species dependent.

ISSN:0143-1161    

DOI:10.1080/01431169608949159

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Two coarse spatial resolution classifications of nominally 1·1 km resolution of deforested areas over a test site covering part of the south-west Amazon basin are compared. One classification is derived from data acquired by NOAA's Advanced Very High Resolution Radiometer (AVHRR) and the other from the ERS-1 Along Track Scanning Radiometer (ATSR-1). A forest/non-forest classification derived from finer spatial resolution ERS-1 Synthetic Aperture Radar (SAR) data is used as a reference for the comparison. Specific patterns of deforestation in the area are identified and their depiction on each of the coarse spatial resolution datasets is examined in relation to their depiction on the fine spatial resolution classification. The results show that significant differences exist between the two coarse spatial resolution classifications and that special rigorous integration methodologies will have to be developed before the results from either source can be used interchangeably with those from the other.

ISSN:0143-1161    

DOI:10.1080/01431169608949160

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

The aim of the study was to examine the spatial autocorrelation and the optimal spatial resolution of optical remote sensing images in a forested landscape. Also the effect of tree species and forest age on this optimum was investigated. Two different methodologies were applied. Semivariograms were used to measure the autocorrelation of pixels while local variance curves were used to define the spatial resolution that maximizes the variance between neighbouring pixels. The range of the semivariograms was 5 m. for Scots pine and 7 m for Norway spruce. Range is also weakly dependent on forest age class. Thereafter sill was found to be strongly dependent on tree species and forest age class. The local variance maximum in infrared and green band was obtained with a spatial resolution of 3 m and in red channel with a resolution of 2 m. Like the semivariance the local variance was at a higher level in spruce and old forests.

ISSN:0143-1161    

DOI:10.1080/01431169608949161

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor

摘要:

Changes in landuse are the outcome of development and the land characteristics of the region. Due to interactive nature, landuse development expands the built-up areas in the course of time. The development of the attraction potentials of towns will change village built-up areas and result in significant growth in the built-up area of the town itself. This interactive relation cited is the reason why the optimal link identification is basically a function of the causes for built-up area development. Because of this fact, the network is identified through the variety of activities in a region. In this study an attempt is made to identify the optimal network from the effect of such development. In addition a further attempt is carried out on orientation of network using the development potential. The rural road network should correlate to the scientific facts of agriculture and demographic characteristics. In the rural areas agriculture and residential development are predominant, so due consideration should be given to identifying an optimal orientation of network. Field and categorized roads are suggested for a rural region to meet the demands of agriculture and residential needs. A relational approach is developed taking into account the road network orientation, parcel yield and dominant wind direction. A geographical direction method is suggested in rural road development and a gradient concept, with a break even point of equilibrium is adopted for optimal network planning.

ISSN:0143-1161    

DOI:10.1080/01431169608949162

出版商:Taylor & Francis Group    

年代:1996

数据来源: Taylor