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891.
We analysed multifrequency 2-dimensional maps of the solar corona obtained with the Nançay radioheliograph during two solar rotations in 1986. We discuss the emission of the quiet Sun, coronal holes and local sources and its association with chromospheric and coronal features as well as with large-scale magnetic fields. The brightness temperature of the quiet Sun was 5 to 5.5 × 105 K at 164 MHz and 4.5 to 5 × 105 K at 408 MHz. A coronal hole, also detected in the 10830 Å He i line, had a brightness temperature of 4.5 × 105 at 164 and 2.5 × 105 at 408 MHz. We give statistics of source brightness temperatures (on the average 8% above the background at 164 MHz and 14% at 408 MHz), as well as distributions in longitude and latitude. Although we found no significant center-to-limb effect in the brightness temperature, the sources were not visible far from the central meridian (apparently a refraction effect). The brightest sources at 164 MHz were near, but not directly above active regions and had characteristics of faint type I continua. At 408 MHz some sources were observed directly above active regions and one was unambiguously a type I continuum. The majority of the fainter sources showed no association with chromospheric features seen on H synoptic charts, including filaments. Most of them were detected at one frequency only. Sources identified at three frequencies (164, 327, and 408 MHz) were located in regions of enhanced large-scale magnetic field, some of them at the same location as decayed active regions visible one rotation before on synoptic H charts. Multifrequency sources are associated with maxima of the green line corona. The comparison with K-corona synoptic charts shows a striking association of the radio sources with dense coronal regions, associated with the coronal neutral sheet. Furthermore, we detected an enhanced brightness region which surrounds the local sources and is stable over at least one solar rotation. We call this feature a coronal plateau and we identify it with the radio counterpart of the coronal neutral sheet. 相似文献
892.
全面、现势的土地利用基础图件是一个国家摸清其土地资源家底,进行土地资源合理利用、规划和科学管理的基础和前提条件。本文从数据源、处理手段与采用的技术方法对土地利用基础图件更新的技术体系进行了研究,基于图件更新技术流程的三个主要环节对图件更新方法进行了系统分析和分类总结,继而提出了一套集RS/GIS/GPS技术于一体的图件更新技术方法与流程;同时依托具有自主知识产权的遥感数据处理平台CASM Im-ageInfo,将整个作业流程一体化,构建了适合我国具体国情的实用和可操作性强的土地利用基础图件更新软件系统,实现了土地利用基础图件的快速更新。 相似文献
893.
Fault Characteristics in Longmen Mountain Thrust Belt,Western Sichuan Foreland Basin,China 总被引:1,自引:0,他引:1
Through field geological survey,the authors found that abundant thrust faults developed in the Longmen (龙门) Mountain thrust belt.These faults can be divided into thrust faults and strike-slip faults according to their formation mechanisms and characteristics.Furthermore,these faults can be graded into primary fault,secondary fault,third-level fault,and fourth-level fault according to their scale and role in the tectonic evolution of Longmen Mountain thrust belt.Each thrust fault is composed of several secondary faults,such as Qingchuan (青川)-Maowen (茂汶) fault zone is composed of Qiaozhuang (乔庄) fault,Qingxi (青溪) fault,Maowen fault,Ganyanggou (赶羊沟) fault,etc..The Longmen Mountain thrust belt experienced early Indosinian movement,Anxian (安县) movement,Yanshan (燕山)movement,and Himalayan movement,and the faults formed gradually from north to south. 相似文献
894.
895.
J.G.P.W. Clevers L. KooistraM.E. Schaepman 《International Journal of Applied Earth Observation and Geoinformation》2008
Canopy water content (CWC) is important for mapping and monitoring the condition of the terrestrial ecosystem. Spectral information related to the water absorption features at 970 nm and 1200 nm offers possibilities for deriving information on CWC. In this study, we compare the use of derivative spectra, spectral indices and continuum removal techniques for these regions. Hyperspectral reflectance data representing a range of canopies were simulated using the combined PROSPECT + SAILH model. Best results in estimating CWC were obtained by using spectral derivatives at the slopes of the 970 nm and 1200 nm water absorption features. Real data from two different test sites were analysed. Spectral information at both test sites was obtained with an ASD FieldSpec spectrometer, whereas at the second site HyMap airborne imaging spectrometer data were also acquired. Best results were obtained for the derivative spectra. In order to avoid the potential influence of atmospheric water vapour absorption bands the derivative of the reflectance on the right slope of the canopy water absorption feature at 970 nm can best be used for estimating CWC. 相似文献
896.
U. K. Shanwad V. C. Patil H. H. Gowda G. S. Dasog 《Journal of the Indian Society of Remote Sensing》2008,36(4):375-386
The current study was taken up to investigate the utility of remote sensing and GIS tools for evaluation of Integrated Wasteland
Development Programme (IWDP) implemented during 1997–2001 in Katangidda Nala watershed, Chincholi taluk, Gulbarga district,
Karnataka. The study was carried out using IRS 1C, LISS III data of December 11, 1997 (pre-treatment) and November 15, 2002
(post-treatment) covering the watershed to assess the changes in land use / land cover and biomass that have changed over
a period of five years (1997–2002). The images were classified into different land use/land cover categories using supervised
classification by maximum likelihood algorithm. They were also classified into different biomass levels using Normalized Difference
Vegetation Index (NDVI) approach. The results indicated that the area under agriculture crops and forest land were increased
by 671 ha (5.7%) and 1,414 ha (11.94%) respectively. This is due to the fact that parts of wastelands and fallow lands were
brought into cultivation. This increase in the area may be attributed to better utilization of surface and ground waters,
adoption of soil and water conservation practices and changes in cropping pattern. The area under waste lands and fallow lands
decreased by 1,667 ha (14.07%) and 467 ha (3.94%), respectively. The vegetation vigour of the area was classified into three
classes using NDVI. Substantial increase in the area under high and low biomass levels was observed (502 ha and 19 ha respectively).
The benefit-cost analysis indicates that the use of remote sensing and GIS was 2.2 times cheaper than the conventional methods.
Thus, the repetitive coverage of the satellite data provides an excellent opportunity to monitor the land resources and evaluate
the land cover changes through comparison of images for the watershed at different periods. 相似文献
897.
V. Nagasubramanian P. V. Radhadevi R. Ramachandran R. Krishnan 《Journal of the Indian Society of Remote Sensing》2008,36(1):27-35
Rational Function Model (RFM) is the alternate sensor Model to the rigorous sensor model that allows end user to perform sensor-independent
photogrammetric processing. Nowadays, commercial off-the-shelf (COTS) digital photogrammetric work stations have incorporated
RFM as a method for image restitution. It is technically applicable to all types of airborne and space borne sensors. In this
paper, we describe the derivations of the algorithmic procedure for third order inverse and forward RFM method for 3-D reconstruction.
Model accuracy is evaluated for aerial image, TK-350 Russian image and IRS-1C PAN image. The results ensure that properly
constructed RFM are accurate enough to be used in place of the original rigorous models. The test results are reported and
summarised. 相似文献
898.
899.
Airborne LiDAR has found application in an increasing number of mapping and Geo-data acquisition tasks. Apart from terrain
information generation, applications such as automatic detection and modeling of objects like buildings or vegetation for
the generation of 3-D city models have been explored. Besides the height itself, height texture defined by local variations
of the height is a significant parameter for object recognition. The paper explores the potential of the analysis of height
texture as a cue for the automatic detection of objects in LiDAR datasets. A number of texture measures were computed. Based
on their definition and computation these measures were used as bands in a classification algorithm, and objects like buildings,
single trees, and roads could be recognized. 相似文献
900.
A. K. Singh P. K. Singh B. Lal A. N. Singh A. Mathur 《Journal of the Indian Society of Remote Sensing》2008,36(2):183-188
A World Bank-aided project on sodic land reclamation in Uttar Pradesh is being executed by U.P. Bhumi Sudhar Nigam, Lucknow,
and Remote Sensing Applications Centre, U.P., Lucknow has the responsibility of sodic land mapping for the execution of land
reclamation programme at the cadastral level. Sodic lands are mainly concentrated in the Gangetic alluvial plains but the
problem of sodicity is particularly acute in the canal-irrigated areas. A study of the distribution pattern of sodic lands
in canal and noncanal command areas in a reclamation site (covering 60 villages out of which sodic lands were mapped in 51
villages) of Etah district in Uttar Pradesh, indicates that 18.39 per cent area of the canal command villages was barren sodic
which was 13.41 per cent of the total geographical area of the site (15417 ha), however, 11.69 per cent area was recorded
to be barren sodic in the non-canal command villages which was only 3.16 per cent of the geographical area of the site. The
results of soil chemical analysis indicate that barren sodic lands of canal command area are saline-sodic with higher concentration
of soluble salts (pH2 >8.5, EC2 >4 dSm−1), however, those of non-canal command area are sodic (pH2 >8.5, EC2 <4 dSm−1). The post-monsoon ground level in the canal-irrigated areas was in the critical and semicritical zone (< 3.0 mbgl) whereas
it was well below the semi-critical zone in the non-canal command area, which indicates that the high ground water level is
a major factor to higher the area under sodicity. 相似文献