Combination of GPS and VLBI on the observation level during CONT11—common parameters,ties and inter-technique biases

Multi-technique space geodetic analysis software has been developed which allows to combine data on the observation level. In addition to local tie information, site-wise common parameters, i.e., troposphere and clocks, can be estimated with this software. Thus, it will be discussed how common parameters have to be estimated and where biases/offsets need to be taken into account. To test such a novel concept, Global Positioning System (GPS) and Very Long Baseline Interferometry (VLBI) data from the CONT11 campaign are being utilized. Since the VLBI baselines of this campaign extend over several thousands of kilometers, GPS data are processed in precise-point positioning mode and satellite orbits and clocks are kept fixed to the IGS final products. From the obtained results, it can be shown that the combination of space geodetic data on the observation level leads to a consistent improvement of station position repeatability as well as nuisance parameters like troposphere estimates. Furthermore, estimation of common parameters (troposphere or clocks) at co-located sites helps to improve the solution further and derive an utmost physically consistent model of the concerned parameters.     

A New Approach to 3D Dense LiDAR Data Classification in Urban Environment

Classification of Mobile Mapping LiDAR (Light Detection and Ranging) data is a challenge in the research community since the day when laser scanner system were integrated and mounted on vehicles for collection of 3D data in urban environment. The approach proposed here for classifying LiDAR data is analogous to the process followed for classifying data from satellite images. Pixel based and segmentation based methods have been employed in past for classifying images obtained from satellites. These methods were based on spectral properties of objects present in the images. But for Mobile mapping LiDAR data this approach has been applied and tested for the first time. The properties of this data are completely different from that of satellite images. So even if the basic approach remains the same, many changes have to be made in the entire classification process. The paper here aims to propose the basic procedure of using pixel-wise classification on dense 3D LiDAR data.     

Computer processing of LANDSAT-1 data and imagery generation

LANDSAT-1 (ERTS-1) data of the complete scene, 1218-04320, covering an area 185 Km x 185 Km in the Godavari Valley, India was computer processed in the Computer Division of the Oil and Natural Gas Commissíon to produce an imagery of readily recognizable land forms. Comparison with the original maps supplied by NASA showed an amazing agreement in quality. Computer oriented data enhancement techniques were developed and the data was reprocessed with the help of these techniques. The resulting imagery reveal an improvement over the originals. The computer software package developed to-date comprises nine different programmes to process the LANDSAT data on the IBM 360, 370 series.     

A complete VLBI delay model for deforming radio telescopes: the Effelsberg case

Deformations of radio telescopes used in geodetic and astrometric very long baseline interferometry (VLBI) observations belong to the class of systematic error sources which require correction in data analysis. In this paper we present a model for all path length variations in the geometrical optics of radio telescopes which are due to gravitational deformation. The Effelsberg 100 m radio telescope of the Max Planck Institute for Radio Astronomy, Bonn, Germany, has been surveyed by various terrestrial methods. Thus, all necessary information that is needed to model the path length variations is available. Additionally, a ray tracing program has been developed which uses as input the parameters of the measured deformations to produce an independent check of the theoretical model. In this program as well as in the theoretical model, the illumination function plays an important role because it serves as the weighting function for the individual path lengths depending on the distance from the optical axis. For the Effelsberg telescope, the biggest contribution to the total path length variations is the bending of the main beam located along the elevation axis which partly carries the weight of the paraboloid at its vertex. The difference in total path length is almost \(-\) 100 mm when comparing observations at 90 \(^\circ \) and at 0 \(^\circ \) elevation angle. The impact of the path length corrections is validated in a global VLBI analysis. The application of the correction model leads to a change in the vertical position of \(+120\)  mm. This is more than the maximum path length, but the effect can be explained by the shape of the correction function.     

Morphostructure of the krishna and the godavari delta region

Morphostructure is a form of the earth’s relief, developed due to tectonic movements. Structures which have undergone movement in the Quaternary time are commonly recognised in areas of low relief and recent deposition. A number of morphpstructures are delineated through geomorphologlcal studies in the Krishna and the Godavari delta region of the coastal Andhra Pradesh which are likely to entrap oil and gas. The morphostructural trends are in confirmation with the known regional trends.     

A note on observation decorrelation,variances of residuals,and redundancy numbers

A technique for processing correlated observations suitable for large, sparse, least-squares adjustments is reviewed. Correlated coordinate differences derived from the Global Positioning System are used as illustrative examples. However, the methods examined are suitable for all types of correlated observations. The computation of variances of residuals, redundancy numbers, and marginally detectable errors is considered for sparse systems.     

A note on palaeozoic bryozoa from the nayar phyllite formation,pauri garhwal,U.P.

This note records the discovery of bryozoan fossils collected from Nayar Phyllite Formation exposed around Satpuli, from a locality SSW of Ira (29° 53′32″: 78° 46′52″) in Pauri Garhwal district, U.P. On the basis of preliminary studies the fossil assemblage has been assigned to the families Phylloporinidae and Fenestellidae. The assemblage tentatively indicates Ordovician — early Silurian age for the formation.     

Comparison of individual and combined zenith tropospheric delay estimations during CONT08 campaign

CONT campaigns are 2-week campaigns of continuous VLBI observations. The IERS working group on combination at the observation level uses these campaigns to study such combinations. In this work, combinations of DORIS, GPS, SLR, and VLBI technique measurements are studied during CONT08. We present different results concerning the use of common zenith tropospheric delay (ZTD) during the combination. We compare the ZTD obtained separately using each individual technique data processing, the combined ZTD, and the ZTD derived from a meteorological model. This resulted in a high level of consistency between each of these ZTD at a sub-centimeter level, a consistency which especially depends on the number of observations per estimated ZTD and the humidity level in the troposphere. We noted that GPS provides the main information about the combined ZTD, the other techniques providing complementary information when a lack of GPS observations occurs.     

Mapping of wastelands through remote sensing techniques and their reclamation—A case study

Wasteland map (1∶100,000) of Rewasa catchment (Sikar district) has been prepared using aerial photographs and Landsat TM imagery. Thematic Mapper data were helpful in identifying the types of wastelands and details could be derived from the aerial photographs. The types of wastelands identified are sands, gullied land, salt affected areas, and barren rocky area. Depending upon the nature of wasteland, suitable rehabilitation measures like plantations, afforestation have been proposed.     

Marine regression along parts of the Indian Coast during the Quaternary — A study using satellite images

Features of marine regression along the Indian Coast during the Quaternary have been studied using the Landsat Imagery for the possible causes and mechanisms of their formation. The occurrence of these features, specially cheniers, is very prominent along the Krishna — Godavari coast. Variations in the inland distances of the cheniers at different locations along the coast indicate differential regressions of the coast at different places. Progradation of the coast and local uplift are identified as the main factors for the same. The topography of the shelf before the regression has played an important role in the development of the regression surfaces of varying widths and the spatial arrangement of the regression features. Morphostructural factors have hindered the formation of deltas along the western coast and also the formation of regression features. Some of the gently sloping coasts without the regression features are the active zones of sediment erosion. The study points to the possibility that some of the coasts/deltas are tectonically active zones. The Krishna Godavari delta is undergoing uplift and the coasts/deltas of the Sundarbans, Mahanadi, Kerala and Saurasthtra are undergoing down-warping. This fact needs to be confirmed using data form deep drillings, geophysical tests and other sources. The confirmation of these phenomena will have a significant effect on the depth of sediment deposition, their maturity and finally on the formation, occurrence and migration of hydrocarbons.     

Building Extraction from LIDAR Point Cloud Data Using Marked Point Process

This paper presents a new algorithm for building extraction from LIDAR (Light Detection and Ranging) point cloud data on the basis of a marked point process based building model. In this building model, the positions and geometries of buildings are modeled by a point process and its marks, respectively. The geometric marks for buildings include their length, width, direction, height. By Bayesian paradigm, a posterior distribution for the marked point process conditional on the LIDAR point cloud data is obtained. The Reversible Jump Markov Chain Monte Carlo (RJMCMC) based scheme is designed to simulate the posterior distribution. Finally, Maximum A Posteriori (MAP) strategy is used to obtain the optimal building detection. The proposed algorithm is tested by a set of LIDAR point cloud data. The results show its efficiency in complex residential environments.     

Morphological evolution of the Krishna delta

The study of the modern delta of the Krishna river has yielded data to identify ancient deltas and their characteristics. Continental landforms like levees and abandoned channels, marine landforms like beach ridges, swamps and spits are recorded from the study of aerial photos. The evolution of the delta is discussed, comparative ages for the landforms arrived at. The history of the delta is reconstructed based on the relationship between the former shore lines and the sub-delta lobes. Delta prospects for oil and gas are indicated at the intersecting zones of the abandoned channels and strandlines.     

Palaeogeomorphic reconstruction of quaternary delta in alluvial plains of West bengal and Orissa

In the vast alluvial plains of West Bengal and Orissa several deltaic plains exist, occurring in an off-lap sequence. These deltas were formed in the background of eustatic fluctuations during the Quaternary Period. They were built partly during rising sea level and pertly during stationary sea level stages. Landform analysis through aerial photographs as well as Landsat imagery interpretation, attested by field study, helped to establish the palaeogeomorphology of these Quaternary deltas. Possible mode of sedimentation during different phases of sea level fluctuations has been worked out     

Further remarks on the altimetry-gravimetry problems

The two Altimetry-Gravimetry linearized boundary value problems, both characterized by gravity anomaly boundary data on the continents, while on the oceans either the gravity potential or its radial derivative is assumed to be known, are investigated in their modified version, in the spherical boundary approximation. A constant unknown bias is added to the data set on the oceans, while a vanishing zerodegree harmonic component is assumed as additional constraint. Existence, uniqueness and regularity results are obtained, it is proved that, in order to obtain regularization of the solution, not only regular data must be imposed, on the continents and on the oceans, but suitable constraints on the coast line are needed.     

PSO-Based Optimal Selection of Zernike Moments for Target Discrimination in High-Resolution SAR Imagery

Target discrimination is the key step of automatic target detection in synthetic aperture radar (SAR) images. In this paper, a new algorithm, effective and robust feature sets for target discrimination in high resolution SAR images has been proposed. Two main steps in target discrimination of SAR images have been developed, the feature extraction based on Zernike moments (ZMs) having linear transformation invariance properties and the PSO based feature selection to select the optimal feature subset of Zernike moments for decreasing computational complexity of feature extraction step. The input regions of interest (ROIs) have been segmented and passed to a number of preprocessing stages such as histogram equalization, position and size normalization. Two groups of Zernike moments (shape and margin (intensity) characteristic) have been extracted from the preprocessed images and they have been applied to the feature selection step. Each group includes 34 moments with different orders and iterations. The selected moments have been applied to a SVM classifier. The proposed scheme has been tested on the MSTAR database. The Receiver Operational Characteristics (ROC) curve and the performance of proposed method using some measured data have been analyzed. Experimental results demonstrate the efficiency of the proposed approach in target discrimination of SAR imagery.     

Geological remote sensing in parts of subarnarekha — baitarani basin,Eastern India

Landsat imagery have been interpreted visually and under Additive Colour Viewer to interpret the regional geology and geomorphology in parts of Subarnarekha-Baitarani basin. The area lies south of Singhbhum shear zone and represents Precamrain shield. Important Simlipal ultrabasic volcanic complex of Orissa is included in the area. Although detailed map of the area is available, yet an attempt has been made to interpret the imagery for evaluating the results provided in comparison to the existing maps. Delineation of main lithological groups is possible. Having some data from the existing maps, lithoiogical boundary delineation of Mica Schist-Phyllite-Quartzite, Granites and Gneisses, Dhanjori Lava, Anorthosite-Gabbro Complex and Dolerite dykes, all of Precambrian age, has been done. Laterite and Quaternary sediments are also picked up. Lineament mapping has been carried out from imagery, which is difficult to map in the field. N--S and NNW-SSE lineament system is very prominent in Simlipal complex whereas in other parts NNW-SSE and NNE-SSW trends are common. The major fault plane running NNE-SSW in the area is responsible for the present-day configuration of Subarnarekha river. Identification of different geomorphological units is perhaps best done on imagery. Several geomorphic units like structural Hill, Denudational Hill, Pediment, Buried Pediment, Lateritic Clay Plain, Laterite upland, Terrace Plain etc have been mapped. Valley fills are wellpicked up from imagery. Hydrogeological potentiality of the different geologic and geomorphic units have been evaluated qualitatively. Ground water occurrence, movement and potentiality are mainly controlled by structural, geological and geomorphological set-up of the area. Buried Pediment, Laterite upland, Laterite clay plain and alluvial fills are the potential zones from the view point of ground water occurrences. Comparative study of the different Landsat bands and band-filter combinations under Additive Colour Viewer has been undertaken to find out the enhancement capability in delineating features. It is found that small scale geological and geomorphological maps can be prepared from Landsat imagery.     

Quantification of carbon stock to understand two different forest management regimes in Kayar Khola watershed,Chitwan, Nepal

The impact of forest management activities on the ability of forest ecosystems to sequester and store atmospheric carbon is of increasing scientific and social concern. This is because a quantitative understanding of how forest management enhances carbon storage is lacking in most forest management regimes. In this paper two forest regimes, government and community-managed, in Kayar Khola watershed, Chitwan, Nepal were evaluated based on field data, very high resolution (VHR) GeoEye-1 satellite image and airborne LiDAR data. Individual tree crowns were generated using multi-resolution segmentation, which was followed by two tree species classification (Shorea robusta and Other species). Species allometric equations were used in both forest regimes for above ground biomass (AGB) estimation, mapping and comparison. The image objects generated were classified per species and resulted in 70 and 82 % accuracy for community and government forests, respectively. Development of the relationship between crown projection area (CPA), height, and AGB resulted in accuracies of R² range from 0.62 to 0.81, and RMSE range from 10 to 25 % for Shorea robusta and other species respectively. The average carbon stock was found to be 244 and 140 tC/ha for community and government forests respectively. The synergistic use of optical and LiDAR data has been successful in this study in understanding the forest management systems.     

A demonstration of 1–2 parts in 107 accuracy using GPS

By interferometric analysis ofGPS phase observations made at Owens Valley, Mojave, and Mammoth Lakes, California, we determined the coordinate components of the71–245–313 km triangle of baselines connecting these sites. A separate determination was made on each of four days, April 1–4, 1985. The satellite ephemerides used in these determinations had been derived from observations on other baselines. Therms scatters of the four daily determinations of baseline vector components about their respective means ranged from a minimum of6 mm for the north component of the71-km baseline to a maximum of34 mm for the vertical component of the245-km baseline. To test accuracy, we compared the mean of ourGPS determinations of the245-km baseline between Owens Valley and Mojave with independent determinations by others using very-long-baseline interferometry(VLBI) and satellite laser ranging(SLR). TheGPS-VLBI difference was within 2 parts in10 ⁷ for every vector component. TheGPS-SLR difference was within6 parts in10 ⁸ in the horizontal coordinates, but83 mm in height.     

A review on the oil & gas prospects of the bengal basin based on photogeomorphological studies

The Bengal basin is a pericratonal basin and holds large thickness of Sediments since the Jurassic to the Recent times. Several wells have been drilled on the stable shelf part of this basin. The geological picture looks encouraging but no oil or gas has been discovered. Structural downwarping in the basin is envisaged during the Miocene times by earlitr workers. Neotectonic movements should have produced new structures which could be reflected on the surface. Geomorphological studies based on aerial photos revealed an ancient shoreline (strandline) in the Hooghly delta to the south of Calcutta. This Strandline is associated with ancient levees, old Channels and morphostructures and opens up a new venue for strandline pool exploration for oil or gas in the Bengal basin.