ISSN:0143-1161    

DOI:10.1080/01431169508954558

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Global Vegetation Index ( GVI) time series of visible, near-IR and thermal IR Advanced Very High Resolution Radiometer (AVHRR)weekly composite data with a 015°spatial resolution collected from NOAA-9 and -11 satellites have been used to develop a prototype global land monitoring system. The system is based on standardized anomalies of the Normalized Difference Vegetation Index (NDVI) and channel 4 brightness temperature ( T4)for the period April 1985-September 1994. Processing included: post-launch updated calibration; cloud screening; filling in the cloud induced data gaps by monthly averaging and spatial interpolation; suppressing residual noise by smoothing; calculating 5-year monthly means and standard deviations of NDVI and T4and their standardized anomalies. The derived anomalies show potential for detecting and interpreting the seasonal cycle and statistically significant interannual variability. Yet, discontinuities and residua! trends can be traced in time series of NDVI and T4. Discontinuities result from the switch from NOAA-9 to NOAA-11 in 1988, and the Mount Pinatubo eruption in 1991. Trends are a combined effect of satellite orbit drift and a possible persistent error in post-launch calibration of solar channels. The orbit drift affects the solar and thermal IR channels through systematic variation of illumination geometry and diurnal heating/cooling of the surface and atmosphere, respectively. Examples are given to illustrate the magnitude of these effects, which reduce the ability to monitor small year-to-year surface changes. The present system yields more accurate results in geographic regions, where atmospheric, angular and diurnal variability effects have a lesser impact on the derived anomalies, i.e. over vegetated areas outside the tropics during local summers. For global-scale monitoring, angular, atmospheric and diurnal variability corrections must be incorporated in the present system.

ISSN:0143-1161    

DOI:10.1080/01431169508954559

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The low resolution APT ( Automatic Picture Transmission) images from NOAA polar orbiting satellites received and recorded by a very small low cost receiver in 4-bit grey scale have been used to produce daily total global solar radiation maps over an area of approximately 1450 km by 890 km. As the APT image is geometrically transformed on board the satellite and because of the reception in the present receiver we have developed a special navigation programme which gives the required accuracy and speed in this application working on an 1BM-AT compatible PC, Root-mean-square errors of 106 and 224 pixels were obtained along and across the nadir track respectively without correction by GCPs. Errors were reduced to 0 5 pixel by a linear transformation using visible land features.

ISSN:0143-1161    

DOI:10.1080/01431169508954560

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Methods for absolute calibration of visible and near-infrared sensors using ocean and cloud views have been developed and applied to channels 1 (red) and 2 (near-infrared) of the Advanced Very High Resolution Radiometer (AVHRR) for the NOAA-7, -9 and -11 satellites. The approach includes two steps. First step is intercalibration between channels 1 and 2 using high altitude (12 km and above) bright clouds as ‘ white’ targets. This cloud intercalibration is compared with intercalibration using ocean glint. The second step is an absolute calibration of channel 1 employing ocean off-nadir view (40-70° ) in channels 1 and 2 and correction for the aerosol effect. In this process the satellite measurements in channel 2, corrected for water vapour absorption are used to correct channel 1 for aerosol effect. The net signal in channel 1 composed from the predictable Rayleigh scattering component is used to calibrate this channel. The result is an absolute calibration of the two AVHRR channels. NOAA-9 channels I and 2 show a degradation rate of 8-8 per cent and 6 per cent, respectively, during 1985-1988 and no further degradation during 1988-1989 period. NOAA-II shows no degradation during the 1989 mid 1991 period. This trend is similar to the calibration trend obtained using desert site observations, the absolute calibration found in this work for both sensors is lower by 17 to 20 per cent ( suggesting higher degradation) from the absolute calibration of Abelet al.( 1993Journal of Atmospheric and Ocean Technology,10, 493-508 that used aircraft measurements. Furthermore we show that application of the calibration of Abelet al.or the present one for remote sensing of aerosol over Tasmania, Australia failed to predict correctly the aerosol optical thickness measured there. The only way to reconcile all these differences is by allowing for a shift of 17 nm towards longer wavelengths of the AVHRR channel 1 effective wavelength. We show that with this shift, we get an agreement between the two absolute calibration techniques ( ± 3 percent), and both of them do predict correctly the optical thickness in the two channels ( + 0.02) Recent work in preparation for publication (Vermoteel al,1995, in preparation indicates that this shift is due to an out of band transmission ( 6 per cent at 900nm) for AVHRR channel 1 previously unidentified.

ISSN:0143-1161    

DOI:10.1080/01431169508954561

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

A steerable dual-channel microwave radiometer was installed on top of an oceanographic tower ofT shore from the Venice lagoon ( Italy) during the calibration experiment of the ERS-1 radar altimeter organized by the European Space Agency. Measurements of atmospheric brightness temperature were carried out over more than two months in the summer 1991. The main objective of the experiment was to obtain the tropospheric electromagnetic excess path length ( AW) required for the correction of the radar altimeter on board the satellite. The instrument calibration and the parameter retrieval algorithms were the main problems to be addressed. The retrieval of other meterological parameters, namely the precipitable water vapour ( K ) and the integrated cloud liquid ( L) was also assessed. An accuracy ( r.m.s.) of about 0-8cm in AH, 01cm inVand 004mm in L is expected, resulting in a significant improvement when compared to those available from conventional meteorological data.

ISSN:0143-1161    

DOI:10.1080/01431169508954562

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The Korucu-Dugla study area ( 225km2) located in western Turkey was selected for the application of Landsat Thematic Mapper ( TM) data to geological studies. A wide variety of image processing techniques including; principal component analysis ( PC) intensity-saturation-hue transformation ( ISH), TM band ratios, and edge enhancement were applied to discriminate the lithologies and structure as well as associated areas of hydrothermal alteration. Colour composites of PCI, 2 and 3, always encoded red, green and blue respectively, PC4, 3 and 2, ISH transformation of TM bands 1, 3 and 5, were found most suitable for lithology and boundary discrimination in the area. A colour composite of 3/ 1, 4/ 3, and 5/ / 7 ratio images was prepared to separate altered areas. Altered areas, which have potential for mineralization, were mapped on the constructed geological map. A number of previously unmapped faults and subunits of the formations were discriminated successfully. A lineament map and rose diagram were prepared using high-pass Laplacian niters. The rose diagram showed a good correspondence with the strike of previously mapped earthquake fault breaks. The linear features of the area have dominant directions at N 30-40°E and N 60-80°E. Alteration and mineralization in the Korucu-Dugla area are mostly controlled by NNE and EW trending structures.

ISSN:0143-1161    

DOI:10.1080/01431169508954563

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The southern part of the Indian Peninsula has long been regarded as a stable area free from Pleistocene tectonics as it represents the Precambrian shield region. But the frequent earth tremors even up to a magnitude of 6-5 ( Richter scale) which occurred in Tamil Nadu have started encouraging the geologists to think that it could possibly be a seismic prone zone. In addition, images acquired by the polar orbiting satellites offered valuable information on the fracture systems and fluvial anomalies suggesting possible Pleistocene tectonism in South India. Hence, a study has been undertaken to evaluate the signatures of Pleistocene tectonism in South India using 1RS-1A, LISS-I FCC imagery ( Indian Remote Sensing Satellite 1A, Linear Imaging Self Scanning 1, False Colour Composite) involving band 2, 3 and 4 under blue, green and red bands respectively

ISSN:0143-1161    

DOI:10.1080/01431169508954564

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Map information for ( 1937-38 and 1965-66) Indian Remote Sensing Satellite (IRS) data of October 1988 and 1990, Landsat-TM data of 1987 and airborne SAR data ( 1988) were used in the identification of river course, geomor-phological features and palaeo channels over part of the Godavari river, India. The change in river course and growth and erosion of the island/ sand bar were measured. The palaeocourse of the river at test sites has been reconstructed. The measured cut-off ratio indicates that the chute cut-off of the river course near Gannavaram is very high. Flood affected areas in the regions could be assessed by this method.

ISSN:0143-1161    

DOI:10.1080/01431169508954565

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

This paper addresses the imaging of swell waves by Synthetic Aperture Radar ( SAR). We give the principles for the determination of swell parameters from image data. Wave height determination is based on a simple method derived from the quasi-linear version of the wave imaging model of Hasselmann and Hasselmann. The influence of wind waves on wave height determination is discussed. Results on coastal swell events observed by ERS-1 off the Banc d' Arguin ( Mauritania) are presented. These results are compared, generally favourably, with estimates from the wave prediction model of Meteo-france and from a model of swell propagation in finite depth water. However, in intermediate to shallow water, SAR wave length estimates were found to be greater than the theoretical values obtained without currents. The results are discussed in terms of swell-current interaction phenomena. A general conclusion of the study is that satellite SAR can be considered as a quasi-operational instrument for swell monitoring at low to moderate wind speeds. Also, we point out that SAR imagery can henceforth be envisaged for physical studies on swell propagation in the coastal zone.

ISSN:0143-1161    

DOI:10.1080/01431169508954566

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The ability to map open surface water is integral to many hydrologic and agricultural models, wildlife management programmes, and recreational and natural resource studies. Open surface water is generally regarded as easily detected on radar imagery. However, this view is an oversimplification. This study used X-bandHHpolarized airborne Synthetic Aperture Radar ( SAR) imagery to examine the potential of SAR data to map open fresh water areas extant on 1:100000 USGS topographic maps. Seven study sites in the U.S.A. with a combined area of over 68000km2were analysed. Detection accuracies and minimum size for detection varied among the seven locations. Size and shape of water bodies and radar shadow all affected detection. However, environmental modulation factors including vegetation and forest cover, moisture, and landscape composition and morphology had the greatest influence and exhibited the most complex role in explaining variability

ISSN:0143-1161    

DOI:10.1080/01431169508954567

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor