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Manas Ranjan Bhuyan Dhani Ram Rajak Markand Oza 《Journal of the Indian Society of Remote Sensing》2007,35(1):43-52
The Advanced WiFS sensor of RESOURCESAT- 1 satellite offers significantly improved specifications compared to the WiFS sensor
onboard IRS IC, P3 and ID satellites. The improvements are in terms of spatial resolution, radiometry (quantisation levels)
and number of spectral bands. In the present study, an attempt has been made to quantify the gains due to these enhanced specifications.
The study has been carried out in a predominantly agricultural area. For the study reported here, one set of overlapping data
acquired on the same day by WiFS and AWiFS sensors has been selected. This eliminates the need of atmospheric correction/
normalization for comparison. The effect of spatial resolution has been studied by applying ISODATA spectral clustering algorithm
with number of clusters set at three different levels, viz., 10, 20 and 30. They are assumed to mimic first, second and third
level classification, respectively. Output images were filtered using 3 × 3 majority filter. Homogeneous polygons having area
less than 1/2 and 1 pixel of WiFS were recorded. This indicates the minimum loss by using WiFS data. A relative gain of 10
– 15 % is observed due to improvement in spatial resolution. For comparison of radiometry, local variance measure was used.
It was observed that local variance is much larger for AWiFS data in comparison with WiFS data. This indicates presence of
enhanced local contrast, hence heterogeneity, in AWiFS data over WiFS data. Separability analysis has been carried out to
demonstrate improvements due to two additional spectral bands (Green and SWIR). 相似文献
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Markand Oza 《Journal of the Indian Society of Remote Sensing》2014,42(1):243-248
Farming is a risky business but, from the food security point of view, it is important that farmers continue to grow crops so that people get food to eat. Although natural calamities cannot be eliminated, its impact can be reduced through implementation of pro-active and pro-poor risk management policy programs. Remote sensing, with capabilities of synoptic coverage, multi-spectral and multi-temporal observations, is ideally suited for in-season monitoring the progress of crop. Normalized Differential Vegetation Index (NDVI) is the primary index for monitoring vegetation status and its temporal behavior captures the dynamic response of vegetation cover to prevailing physical conditions. The present study offers a methodology for making multiple inseason assessment of the crop growth vis-a-vis its normal performance. This is treated by use of conditional distribution. Present analysis reports the performance in deriving spectral maxima (Gmax) from complete profile of validation season and one which was derived from conditional mean approach. It was observed that in more than 90 % of the cases, the difference in Gmax was less than 3 %. Thus the performance of methodology can be termed as very good. 相似文献
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Markand P. Oza 《Journal of the Indian Society of Remote Sensing》1989,17(2):23-26
Selection of band combination for generating a colour composite image using IRS data is discussed from statistical considerations. Most suitable three band combination turns out to be bands 1, 3 and 4. It is also shown that intrinsic dimensionality of IRS data is approximately two. 相似文献
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Analysis of the physical, chemical and biological parameters assessing water quality in Harris Neck estuary indicated that the average dissolved oxygen level was 8.6 mg/L, it maintained moderate levels of total dissolved nitrogen (2.7-4.6 mg/L) and total dissolved phosphorous (<0.05 mg/L), chlorophyll a was above 5.0 μg/L and it is contaminated with low levels of fecal bacteria. Bifidobacterium adolescentis, a putative marker of human fecal pollution, was detected once at stations 3 and 5. Overall the Harris Neck water quality analyses indicated a relatively pristine and a healthy functioning marine environment. 相似文献
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Traditional and molecular methods (PCR) were used to detect, quantify and identify the source of fecal pollution in coastal sites of Puerto Rico and Trinidad. Enterococci and Escherichia coli standard plate counts were used as a general indicator of fecal contamination while the PCR detection of Bifidobacteria adolescentis and human or bovine specific Bacteroidales were used to examine potential sources. Seven of 14 sites in Trinidad including Maracas Bay which is a major public beach contained significant fecal contamination based on enterococci numbers counts exceeding established thresholds for areas of direct contact. Forty six percent of the 27 stations in Puerto Rico were over the established thresholds for enterococci and 49% according to E. coli counts. About 31% of the stations examined in Puerto Rico had evidence of human derived fecal contamination. Human fecal pollution was detected in only one station from Trinidad. Bovine derived contamination was detected only once. 相似文献
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Markand Oza 《Journal of the Indian Society of Remote Sensing》1993,21(3):179-183
The optimal selection of spatial resolution for a remote sensing based study is very important. Two methods, one based on local variance and the other based on semi-variance at lag 1, available for arriving at a solution of this problem are tried out in this study. The areas covered are agriculture-dominated regions of North Gujarat and Western Uttar Pradesh. SPOT-1 HRV multispectral data were analysed. It was found that the optimal spatial resolution is about 60–80 m. 相似文献
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