Baldev Sahai

Spectral response of rice crop and its relation to yield and yield attributes

Abstract Ground-based radiometric measurements were conducted on six varieties of rice crop during an entire growth cycle using a hand-held seven-band radiometer. Concomitant measurements of some of the yield attributes were also made. Spectral data were also collected on a single variety grown under 12 different fertilizer treatments. Spectral data have been correlated with leaf area index, total wet biomass, total dry biomass, plant water content and final grain, straw and total yield. The results show similar temporal spectral responses of all six varieties and a strong correlation of agronomic parameters with spectral parameters derived from the near-infrared and red radiances. Red and near-infrared radiance ratio and normalized differences were found sensitive to the N fertilizer application but not to the P and K fertilizers. Linear correlations were observed between spectral parameters and final grain, straw and total yield

Coastal morphology: a case study of the Gulf of Khambhat (Cambay)

Abstract Geomorphic processes greatly influence the industrial, commercial and recreational activities in the Gulf of Khambhat (Cambay). LANDSAT data with their synoptic and repetitive coverage have been used in studying the distribution of suspended sediments, currents and fronts and for mapping shoreline configuration and wetlands. Visual interpretation of LANDSAT Multispectral Scanner (MSS) band 6 and 7 images and diazo colour overlays was carried out for the above purpose. Colour density slicing was performed on all four MSS images for the qualitative estimation of suspended sediments. The observation of suspended sediments suggests that during the monsoon many sediments brought in by various rivers remain in suspension and start settling down with the onset of the winter season. Tides also play an important role in the movement of the suspended sediments and fronts. The concentration of the suspended sediments is high on the mainland side during the flood tide and in the centre of the Gulf during the...

Mapping of salt-affected land in Saurashtra coast using Landsat satellite data

Abstract Coastal salt-affected land is subject to variation in area as well as magnitude with time because of influence of coastal processes. In order to take corrective and protective measures, it is essential to have accurate information about such an area in the form of maps. Using conventional ground methods, mapping of such an inhospitable area is not only difficult and time-consuming but also expensive, laborious, and associated with vagaries of weather. Hence an attempt has been made to use remote sensing techniques for the purpose of preparing a map of one of the coastal areas of Gujarat state, providing information about the extent and magnitude of salt-affected land.

Ecological studies in the Ukai command area

Abstract The present study was directed towards studying the impact of the Ukai-Kakrapar irrigation project on the ecology of the command area with particular reference to changes in cropping pattern and land degradation due to waterlogging/salinity. The data used were multitemporal (1972-1981) LANDSAT imagery of the entire command area, multitemporai colour infrared plus black-and-white aerial photography and multispectral scanner data over a test area of about 1200 km2 collected from November 1980 to February 1982. Land-use maps for the entire command area at 1:250 000 scale (LANDSAT) and land-use/cropping-pattern maps for the test area at 1:12 500 scale (aerial photography) have been prepared. The results indicate that due to the introduction of large-scale irrigation, the cropping pattern has changed and the acreage under heavy perennial crops such as sugar-cane and banana has increased beyond permissible limits resulting in a rapid rise in the water-table in the area. The areas delineated as waterlog...

Comparison of SPOT, TM and MSS data for agricultural land-use mapping in Gujarat (India)

Abstract Remote sensing technology is finding increasing acceptance as a useful, reliable and timely tool for preparing agricultural land-use inventories. Since a variety of data from different sensors are now available to the user, a comparison of SPOT, TM and MSS data for agricultural land-use mapping has been attempted in Himatnagar taluka, Sabarkantha district, Gujarat, India, using SPOT multispectral data (19 September 1986) and TM and MSS data (22 September 1986) for evaluating their efficacies. The study comprised of radiometric comparison, spatial gradient analysis, and unsupervised and supervised classification of common test sites. This study was restricted to analysis of 3 bands of TM and MSS corresponding to those of SPOT. SPOT data showed lesser variability (as measured by coefficient of variation) compared to TM, whereas other radiometric characteristics are similar. Visual interpretation of SPOT and TM FCC at 1:25,000 scale shows that delineation of individual fields, small built-up areas and roads are easier in SPOT than TM. Supervised classification shows that within-class variability is less in SPOT compared to TM and statistical class separability is higher in SPOT.

Geochronological studies of strandlines of Saurashtra, India, detected by remote sensing techniques

Abstract Using remote sensing techniques four strandlines parallel to the present coastline were detected in the 16-18 km wide coastal belt of the Saurashtra peninsula in western India. Geochronological studies of themiliolites, the principal deposit of this area, using the 230Th/234 method, yielded ages ranging from 52 to 235 thousand years. With strong evidence in favour of tectonic instability in the region, the average uplift rates of the standlines are calculated to range from 0-12 to 0p 58 mm/year.

An optimal estimation technique for increasing the accuracy of crop forecasts by combining remotely sensed and conventional forecast results.

Abstract An optimal estimation (OE) technique has been used to increase the accuracy of crop acreage and yield estimates by combining results from remotely sensed (RS) data and conventional models. For crop acreage estimation the OE increased the accuracy of wheat acreage estimation when the first forecasts of the Directorate of Economics and Statistics (DES) were combined with state level RS estimates over the states of Haryana and Punjab in India. To increase the accuracy of wheat yield forecasts an autoregressive (AR) model was developed. Results of AR model were optimally combined with RS-based estimates for Hisar and Karnal districts in Haryana, India. The OE results for a total of eight forecasts had a lower mean absolute per cent deviation than the forecasts using RS and AR approaches. The power of OE was further demonstrated by combining weather-based wheat yield model results for the state of Punjab (India) with first order AR model results, suggesting an increase in accuracy of forecasts by opti...

Land-use survey of Idukki District

Abstract The growing population pressure and limited availability of land necessitates proper utilization of the available land through scientific land-use planning. Realizing this fact, a project using multiband aerial photography was taken up with following objectives: identification and mapping of areas under various land uses, study of geomorphology, identification of potential groundwater areas and identification of areas requiring soil conservation and reclamation measures. The major land-use classes mapped are agriculture, forest, wasteland, water bodies and public use. These are further subclassified. Some of the important observations are the reduction in the area under forest and the existence of a large area under wasteland. Geomorphological maps prepared depict slope, relief, drainage and vegetation. With the help of structural and geomorphological maps, the technique of identifying potential groundwater areas has been demonstrated. The land-use maps have a classification accuracy of 86 per ce...

Ground water exploration in the Saurashtra peninsula

Abstract The fact that groundwater in hard-rock formations is generally confined to fissures, fractures, joints and weathered zones makes space imagery extremely useful when prospecting for groundwater in hard-rock areas. Keeping this in mind, multitemporal LANDSAT imagery of the Saurashtra region has been studied by employing visual/manual-interpretation techniques. Various hydrogeomorphological features, such as abandoned channels, buried channels, lineaments, water bodies, vegetation and floodplains, were mapped at a scale of 1:250 000. Using these maps, areas with groundwater potential were identified. Resistivity surveys were conducted in selected areas. Using these results, sites for exploratory drilling were chosen. The pumping-test results at most of the sites were quite encouraging. The present study therefore demonstrates the usefulness of remotely sensed data in groundwater exploration.

Integrated resources survey and applications

Comprehensive, reliable and up-to-date information on natural resources is a prerequisite for undertaking planned development activities. Integrated resources survey conducted by a multidisciplinary team brings out the inter-relationship of the resources and enables their planned and judicious exploitation. Remote sensing techniques are ideally suited for this purpose as the same data base is utilized by various disciplines. Multistage sensing facilitates reconnaissance, semi-detailed and detailed type of information. Surveys conducted in the Idukki district of Kerala and the Bundelkhand region of Uttar Pradesh are illustrated in this paper. These surveys generated thematic maps and statistical data on various resources. Information obtained has been extremely useful for resource managers and decision makers.