Evaluation of microwave remote sensing data for forest stratification and canopy characterisation

The study presents digital preprocessing techniques, visual mapping capability of airborne X-band SAR data having diverse vegetation types in tropical wet climate. Spatial textural analysis methods have also been evaluated to enhance discriminability of the forest types and features. Attempt has been made to enhance the information by merging optical remote sensing data with microwave X-band response. Finally, the backscattering digital values have been correlated with qualitative and quantitative vegetation parameters. The Leaf Area Index has shown significant relationship with SAR image digital number value.     

Procedures for computation of saturation radiances: A case study for proposed sensors onboard Indian remote sensing satellite-1C

Saturation radiance (SR) is one of the important parameters required while designing a sensor and it depends on application requirements as well as sensor requirements. This study describes the procedures for computation of SR values using theoretical calculations of earthatmosphere radiances as well as radiances observed by existing satellites such as IRS-1A/1B LISS-I, Landsat TM and SPOT sensors. A possible set of saturation radiances for IRS-1C LISS-III, WIFS and PAN sensors has been suggested.     

Crop acreage estimation using ERS-1 SAR data

Synthetic Aperture Radar (SAR) data from the European Remote Sensing Satellite (ERS-1) acquired in July, October and November, 1992 covering the kharif season of the region were used separately and in combination to identify the major crops and for estimation of their acreage before harvest Separability indices were calculated for major cover types and it was found that single-date SAR data cannot be used for accurate identification of various crops. Multi-temporal colour composite facilitated better identification of crop types. Comparison of area estimates made with ERS-1 SAR and IRS-1B LISS II data showed that the commonly used digital data analysis techniques (per pixel classifiers) are not adequate for accurate estimation of crop acreage using SAR data.     

Planform analysis of Hooghly river metamorphosis using multidate satellite data

Conventional techniques of monitoring both long-term and short-term changes in river morphology is time consuming and expensive. Remote sensing with its synoptic and temporal capability is an effective tool to study river metamorphosis. The present study is carried out in lower Ganga basin where Hooghly river is an important river contributing sediment to this vast fertile plain. A time series planform analysis is carried out between 1971 to 1991 period. Thematic maps generated from Landsat MSS and IRS-IA LLSS-I satellite data for 1986 and 1991 period respectively is compared with 1971 topographic maps. The migratory character of paleocourse of Hooghly river is deciphered through the paleochannels, oxbow takes and meander scars deciphered from satellite imagery. The shortterm river metamorphosis like cut-offs, bar migration and point bar accretion morphology are mapped and compared with 1971 topographic maps. The critical zone with respect to cut-offs and future channel migration are identified for river stabilization work.     

Evaluation of Cartographic accuracy of IRS-1A LISS II data for upgrading linear details on the existing maps (A case study of Chandigarh area)

Considering the fest pace of development, up-to-date maps have become imperative in developmental planning. Conventional map updating techniques are expensive and time consuming. The present paper makes an attempt to tackle the problem using GIS techniques. Maps generated from IRS-1A LISS II data and Survey of India (SOI) toposheets were used as input maps in GIS. These maps were overlaid to obtain the positional errors at road junction points. The area statistics of each sector were calculated taking the SOI map as reference data. The results show that the areas calculated from LISS II data and SOI map are well comparable and the deviations are within 10%, whereas the positional accuracy (MSE) of points is within 30 m. The study demonstrates that the IRS-1A LISS II data can be used for updating of maps on scale 1:100,000 and smaller in areas where linear features are identifiable in the IRS LISS II image.     

Area estimation of arecanut plantations in Sirsi Taluk using IRS data

Extent and distribution pattern of arecanut plantations in Sirsi Taluk, Uttara Kannada District, Kamataka have been studied using IRS, LISS II data. The plantations are found to exhibit perfect zonality, distinct structure and contrasting tonal characteristics and thereby enable their differentiation from other land use/land cover categories encountered in the area. The study not only established the utility of IRS data in acreage estimation of this unique category of land use having significant economic relevance in the area but also in assessing the scope for planning development of spices in these plantations.     

A package for digital processing and automatic contouring of aeromagnetic data

Aeromagnetic data processing refers to the processing of magnetic data acquired through airborne surveys. The total magnetic field at various points along the predetermined flight path is recorded using the on board cesium magnetometer. At each of these points, the positional information in terms of latitude, longitude obtained from Inertial Navigation System (INS) and attitude, time and date are also recorded. The track flown by the aircraft while data acquisition is also recorded using video flight path camera. A software package has been developed to process this data and generate outputs in a form amenable to visual interpretation. It is developed on a VAX 11/780 system using VAX FORTRAN and PLOT 10 GKS software. This paper gives an outline of the various functions available in this package and also highlights the problems encountered in choosing the most appropriate techniques/methods to be used in the gridding and contouring of the data.     

Potential of satellite data in delineation of wastelands and correlation with ground information

In the present study an attempt has been made to delineate the wastelands at microlevel in Matar taluka of Kheda district. IRS OSS II digital data of 1991 has been used for the study which was analysed on VAX 11/780 image processing system. The digital data was classified following supervised classification algorithm. The three types of wastelands namely waterlogged, pasture/grazing and salt affected lands could be identified and mapped. The area statistics for the different wasteland categories present in the taluka were generated. Chemical analysis was also carried out for soils collected from different categories of wastelands to understand the exact nature of soils of each category.     

Spectral reflectance characteristics of salt-affected arid soils of Rajasthan

The spectral reflectance characteristics of different types of natural and anthropogenic salt-affected soils have been studied under field conditions. The spectral reflectance value for non-saline and all types of salt-affected soils was maximum in near infra red region (800–1000 nm). The natural salt-affected soils having surface salt encrustation showed highest reflectance value followed by the sodic soils (formed due to high residual sodium carbonate water irrigation) natural saline soils and saline soils due to saline water irrigation. Soil texture, pH, CaC0₃ and organic matter together accounted for 29.6% variation in the maximum reflectance percentage value out of which only pH accounted for more than half (14.2% variation).     

Forest cover mapping of East district,Sikkim using IRS-1A LISS II satellite data

Remote sensing techniques have been applied to classify tour density classes within each of the forest type along with other major landuse/landcover classes in the East district, Sikkim using IRS-1A LISS II satellite data pertaining to the period of November, 1988. The shadow problem in rugged terrain and difficulty in acquiring cloud free data for different seasons pose problems to achieve considerable mapping accuracy. In the present study, the forests of the district were delineated through supervised classification techniques using maximum likelihood algorithm into five forest types as sal forests, subtropical broad-leaved forests, Himalayan wet temperate forests, Rhododendron forests and alpine forests. The alpine forests were further stratified into two categories as moist alpine scrub and dry alpine scrub. The statistical data obtained from the present study shows that 55.47 percent of the total geographical area of the East district was under forest cover. An overall accuracy of more than 85 percent in correctly delineating forest classes was achieved.     

Change detection study of islands in Hooghly estuary using multidate satellite images

River estuarine environment constitutes a highly dynamic fluvio-morphological setting where processes of accretion and deposition are active. Hooghly estuary, being one of the largest of estuaries in the east coast of India, needs constant monitoring. Multidate satellite images of IRS-1A L1SS-I and Landsat MSS for 1975–1991 period are studied to detect long term morphological changes in this estuary. The study reveals that the estuarine islands like Sagar, Ghorarmara and Suparbhanga are eroding whereas Lohachara islands has completely eroded off Nayachara island near Haldia due to its shape and size bifurcates the river into two channels. The island as revealed from Satellite images is in accretional phase where the total surface area has increased. The study, therefore, indicates that constant monitoring of spatial and temporal changes in this type of environment would help to understand physical processes.     

Stratification approach for forest cover type and landuse mapping using IRS-1A LISS-II data — A case study

Indian Remote Sensing Satellite-1A (IRS-1A) LISS-II data of 24th Nov., 1988 was analysed digitally to differentiate three density classes viz. dense/closed forest, open forest and degraded forest within each vegetation type in the district, Jalpaiguri, West Bengal. Stratification approach was used to classify separately forest cover into pure sal forests, mixed forests, riverine forests along with man-made sal/teak plantations. In this approach the forested and non-forested areas were classified separately through supervised classification techniques using maximum likelihood algorithm using VAX 11/780 based VIPS-32 Image Processing software. Later the two classified outputs were composited to provide entire area of the district. The forest cover of the district was 1420.89 sq. km, (22.82 percent). Other broad landuse/landcover dominant in the district include agricultural areas.(45.20 percent) and tea gardens (10.49 percent). The accuracy of the classified output was estimated to be 90 percent for forested areas and 85 percent in case of other landuse/landcover classes.     

Ranchi mega lineament and its correlation with geological and geophysical data

Remotely-sensed satellite data of Landsat 5 (TM) and IRS-1A (LISS II) covering parts of central portion of Chotanagapur plateau have been analysed visually to delineate some prominent lineaments in Ranchi district and its adjoining area. One of the most prominent lineament “Ranchi mega lineament? has been analysed in this paper. This lineament is a potential site for base metal mineralisation at some places, and it acts as good groundwater conduit in the region. No earlier attempt to map this entire structural unit as a separate entity is known. Geophysical bouguer gravity anomaly map, lithological and structural maps have some remarkable correlation with this lineament. In the present paper authors have tried to analyse the lineament with respect to its tectonic, mineralisation and groundwater prospects. Resistivity survey carried in close proximity of this lineament at selected sites, indicate that rocks are well fractured at depth. Available lithological and structural map support this lineament as a shear near Purulia (W.B.) and also having base-metal mineralisation potential in this area. Authors opine that existing gravity anomaly map may be further augmented in the light of present study.     

Assessment of sediment distribution pattern in the Tungabhadra reservoir using satellite imagery

In order to understand the dynamic aspects of suspended sediments in an inland water body, Tungabhadra reservoir on the Tungabhadra river in the Krishna basin was studied. The study has been carried out using Landsat MSS and IRS-1 A LISS-II images. Visual interpretation techniques have been used to obtain information on the location and extent of sediment distribution pattern in the water-spread area of the reservoir. It has been possible to monitor the seasonal fluctuations in the reservoir water-spread; measure corresponding fluctuation in the volume of water in the reservoir, and study seasonal changes in the suspended sediment distribution pattern in the reservoir. An attempt has also been made to prepare area capacity curve for the reservoir. Semi-quantitative assessment of sediment deposits between reservoir levels were made considering water spread area from the satellite images (May 1986, April 1987, Jan. 1988, Jan. 1989 and March 1989) and sedimentation survey report of KERS 1985, (Karnataka Engineering Research Station). The results indicated that the high Concentration of sediments is at the western confluence of the Tungabhadra river. On the basis of tonal variation as observed, the reservoir could be divided into four major zones, viz., very high and high at the river confluence, moderate at the periphery and low at the dam site.     

Assessment of soil degradation Hazards in Jalor and Ahor Tehsil of Jalor district (Western Rajasthan) by remote sensing

In the present study efforts have been made to identify and map areas affected by various land degradation processes with the aid of Landsat TM imagery data of 1988 and ground truth verification. The kind, extent and degree of land degradation have been mapped. In an area of over 4,124 sq. km. 51% was affected by water erosion and 30% area by wind erosion. Nearly 1.14% area is affected by salinity. Degradation due to combined effect of water and wind erosion and water erosion and salinization has affected 8.20% of the study area. 1.53% area is free from any hazard. Remaining 7.85% area comes under hills and rivers. Nearly 44 percent of the affected area is subjected to moderate and severe degradation which can easily be combatted by techniques referred.     

Delineation of social forestry plantations under various afforestation programmes using satellite digital data

Digital analysis of IRS 1A LISS-II (23-03-1991) data was used to delineate social forestry plantations in Matar taluka of Kheda district, Gujarat. VAX 11/780 image processing system was used to categorise the various plantations using supervised maximum likelihood classification. The classified output yielded three categories of plantations viz.,Eucalyptus spp.,Acacia spp., and mixed spp. The statistics for all the categories were also generated.     

Differentiation of oil seed crops by remote sensing based on their spectral reflectance pattern

The feasibility of differentiating four oil-seed crops viz., mustard, toria, yellow sarson and sunflower, based on their spectral reflectance in the visible and near infra red region was studied in a field experiment, The spectral vegetative index profiles, generated during the growth period of different oil seed crops indicated two vegetative growth peaks and a depression between the two peaks, due to the conspicuous yellow colour of flowers, which masked the green leaves. The magnitude of such depression in the spectral vegetation indices viz., ‘Greenness’ and ‘Perpendicular Vegetation Index’ (PVI), were of higher magnitude in yellow sarson. The flowering period parameters viz., flowering time, duration and intensity, deduced from the spectral vegetation indices were found to be beneficial in differentiating different oil-seed crops by remote sensing. A plot of ‘Brightness’ vs. ‘Greenness’ values determined during the growth of the crops formed typical clusters. The cluster representing toria crop was significantly different from the other crops, thereby making toria identifiable from others by remote sensing.     

On the equivalence of spherical splines with least-squares collocation and Stokes’s formula for regional geoid computation

This work is an investigation of three methods for regional geoid computation: Stokes’s formula, least-squares collocation (LSC), and spherical radial base functions (RBFs) using the spline kernel (SK). It is a first attempt to compare the three methods theoretically and numerically in a unified framework. While Stokes integration and LSC may be regarded as classic methods for regional geoid computation, RBFs may still be regarded as a modern approach. All methods are theoretically equal when applied globally, and we therefore expect them to give comparable results in regional applications. However, it has been shown by de Min (Bull Géod 69:223–232, 1995. doi: 10.1007/BF00806734) that the equivalence of Stokes’s formula and LSC does not hold in regional applications without modifying the cross-covariance function. In order to make all methods comparable in regional applications, the corresponding modification has been introduced also in the SK. Ultimately, we present numerical examples comparing Stokes’s formula, LSC, and SKs in a closed-loop environment using synthetic noise-free data, to verify their equivalence. All agree on the millimeter level.     

Geoinformatic Modeling of Groundwater Resource Mapping of Shear Zone Regions- A Case Study on Attur Valley,Tamil Nadu,India

The general tendency of mapping groundwater resource using remote sensing and Geographic Information System (GIS) techniques involve assigning higher weightage to geomorphology. But this cannot be used as a thumb rule everywhere, especially an area where many ductile and brittle zones are prevalent. The influence of texture and structure of sheared rocks might play a control over retaining and permitting groundwater to flow. Attur valley is characterized by the presence of many shear zones and faults and hence the rocks are highly fissile within the shear zones. The present study tries to establish a new ranking and weightage scheme and hence a new spatial model for groundwater resource mapping in shear zone area like Attur Valley. This spatial model can be verified with field data such as water level data, pump test and resistivity data.     

Geomorphological study of Bulandshahr District (U.P.) using remotely sensed data

Remote sensing data pertaining to LANDSAT TM FCC of bands 2, 3 and 4 of 9th May 1991 and IRS-1A LISS II digital data of 3rd May 1991, have been utilized for the study of geomorphology of Bulandshahr district, U.P. Visual interpretation technique has been followed for geomorphological mapping and the area has been separated into four broadly defined geomorphic zones, namely Varahasi Older Alluvial Plain, Aligarh Older Alluvial Plain, Terrace Zone and Recent Flood Plains of Ganga and Yamuna, each characterized by its own geomorphic/landform elements discernable on remote sensing data. The Varanasi Older Alluvial Plain represents the oldest geomorphic surface occurring at highest tectonic level in the Gangetic plain. The Aligarh Older Alluvial Plain represents a palaeo-flood plain of a north flowing palaeo-drainage in the area. The Terrace zone represents the older flood plain of Ganga and its tributaries. The Recent Flood Plains of Ganga and Yamuna rivers, which get periodically inundated, constitute the youngest geomorphic surface in the study area. Digital image processing outputs, particularly ratio images have been found to be helpful in identifying certain geomorphic landforms (old/abandoned channels, scars etc.) due to greater contrast within ratio images.