An eminent scientist and engineer in the field of Geodesy and Earth Sciences. Having deep interest in geoid modelling, tidal measurements, gravimetry and geomagnetism.
Journal Of The Institution Of Engineers (india): Series A, Oct 30, 2017
Engineering projects require orthometric heights of points where as Global Navigation Satellite S... more Engineering projects require orthometric heights of points where as Global Navigation Satellite System (GNSS) provide height above ellipsoid. Thus, to make use of GNSS in engineering surveying, the relationship between ellipsoidal height and orthometric height as a function of position needs to be established through geoid modeling. In this study, an attempt has been made to develop a geoid model using the geometric method. Observations were taken in a network of sixteen stations spread over 600 km 2 around Dehra Dun, India. GPS observations were taken using dual frequency geodetic GPS receivers and leveling done using digital levels with 0.1 mm accuracy. Orthometric height of stations from developed model have been found to be near to those from field levelling which is considered most accurate. Further, the values have been compared with those obtained from the recent GOCE-GRACE-LAGEOS geoid model EIGEN6C3stat. It has been found that the geometric model provides far better accuracy than that obtained from the global geoid model. Therefore, it can be concluded that the geometric method of geoid modeling can better be used for reduction of GPS observed ellipsoidal height to orthometric height in a local area. This model may gainfully be employed in a project area as a substitute for densification of leveling lines, thereby reducing the project cost substantially.
Journal of Surveying Engineering-asce, Aug 1, 2016
AbstractCivil engineering projects require the orthometric height of points (i.e., the height of ... more AbstractCivil engineering projects require the orthometric height of points (i.e., the height of points above geoid). Thus, to make use of the Global Navigation Satellite System (GNSS) in engineering surveying, geoid undulation (i.e., the separation between an ellipsoid and geoid surface) must be known. In this study, an attempt has been made to determine the geoid undulation using the astro-geodetic method. Observations were taken in a network of seven stations spread over 300 km2 around Dehra Dun, India. Astronomical observations of seven stars belonging to different constellations were taken with a theodolite having a least count of 1.0 s. Global positioning system (GPS) observations were taken using dual-frequency geodetic GPS receivers with a 0.1-mm-accurate digital level. Values of astro-geodetic geoid undulations (of stations) have been found close to that computed from field levelling. Further, the values have been compared with those obtained from global geoid models such as EIGEN6C3stat and EGM2...
observations and topography information for development of geoid models (yildiz et al. 2012). The... more observations and topography information for development of geoid models (yildiz et al. 2012). The reliability of the gravimetric models, in terms of spatial resolution and accuracy, has been found to be improved by combining models with geoid undulations from GPS data/field levelling (Smith, Milbert 1999). Based on this, jGEOID 2000, a gravimetric geoid model of japan, has been updated with the geoid undulations from a network of GPS Bench Marks (B.Ms) spread over japan. It yielded to a new hybrid geoid model GSIGEOID2000, which during evaluation provided a precision (standard error) of the order of 4 cm throughout the whole of japan (Kuroishi et al. 2002). GEOID09, a hybrid geoid height model, developed by the National Geodetic Survey (NGS) US using US Gravimetric Geoid 2009 (USGG2009) gravity model along with GPS and field levelling data. An evaluation UDK 528.21
Site specific geoid model is prerequisite for accurate determination of orthometric heights. No g... more Site specific geoid model is prerequisite for accurate determination of orthometric heights. No geoid model has been developed so far for India or any of its part. So, development of a geoid model for India or its part is of utmost need to make use of GNSS data towards determination of orthometric heights. In this research work, an attempt has been made to develop geoid undulation models by gravimetric method using Molodensky’s concept. Component parameters in line with the Remove – Compute – Restore (RCR) technique have been used recursively. Models have been developed for two study areas: one of these lies in and around Dehradun (30° 19′ N, 75° 04′E) in Uttarakhand state, India in lower Himalayan region having highly undulating topography and the other near Hyderabad (17° 30′N, 78°30′E) in Telengana state of India having gentle topography. The model has been tested for 7 stations in the first study area and accuracy has been found to be 17.5 cm; whereas, for the second area accura...
Journal of The Institution of Engineers (India): Series A, 2017
Engineering projects require orthometric heights of points where as Global Navigation Satellite S... more Engineering projects require orthometric heights of points where as Global Navigation Satellite System (GNSS) provide height above ellipsoid. Thus, to make use of GNSS in engineering surveying, the relationship between ellipsoidal height and orthometric height as a function of position needs to be established through geoid modeling. In this study, an attempt has been made to develop a geoid model using the geometric method. Observations were taken in a network of sixteen stations spread over 600 km 2 around Dehra Dun, India. GPS observations were taken using dual frequency geodetic GPS receivers and leveling done using digital levels with 0.1 mm accuracy. Orthometric height of stations from developed model have been found to be near to those from field levelling which is considered most accurate. Further, the values have been compared with those obtained from the recent GOCE-GRACE-LAGEOS geoid model EIGEN6C3stat. It has been found that the geometric model provides far better accuracy than that obtained from the global geoid model. Therefore, it can be concluded that the geometric method of geoid modeling can better be used for reduction of GPS observed ellipsoidal height to orthometric height in a local area. This model may gainfully be employed in a project area as a substitute for densification of leveling lines, thereby reducing the project cost substantially.
AbstractCivil engineering projects require the orthometric height of points (i.e., the height of ... more AbstractCivil engineering projects require the orthometric height of points (i.e., the height of points above geoid). Thus, to make use of the Global Navigation Satellite System (GNSS) in engineering surveying, geoid undulation (i.e., the separation between an ellipsoid and geoid surface) must be known. In this study, an attempt has been made to determine the geoid undulation using the astro-geodetic method. Observations were taken in a network of seven stations spread over 300 km2 around Dehra Dun, India. Astronomical observations of seven stars belonging to different constellations were taken with a theodolite having a least count of 1.0 s. Global positioning system (GPS) observations were taken using dual-frequency geodetic GPS receivers with a 0.1-mm-accurate digital level. Values of astro-geodetic geoid undulations (of stations) have been found close to that computed from field levelling. Further, the values have been compared with those obtained from global geoid models such as EIGEN6C3stat and EGM2...
Journal Of The Institution Of Engineers (india): Series A, Oct 30, 2017
Engineering projects require orthometric heights of points where as Global Navigation Satellite S... more Engineering projects require orthometric heights of points where as Global Navigation Satellite System (GNSS) provide height above ellipsoid. Thus, to make use of GNSS in engineering surveying, the relationship between ellipsoidal height and orthometric height as a function of position needs to be established through geoid modeling. In this study, an attempt has been made to develop a geoid model using the geometric method. Observations were taken in a network of sixteen stations spread over 600 km 2 around Dehra Dun, India. GPS observations were taken using dual frequency geodetic GPS receivers and leveling done using digital levels with 0.1 mm accuracy. Orthometric height of stations from developed model have been found to be near to those from field levelling which is considered most accurate. Further, the values have been compared with those obtained from the recent GOCE-GRACE-LAGEOS geoid model EIGEN6C3stat. It has been found that the geometric model provides far better accuracy than that obtained from the global geoid model. Therefore, it can be concluded that the geometric method of geoid modeling can better be used for reduction of GPS observed ellipsoidal height to orthometric height in a local area. This model may gainfully be employed in a project area as a substitute for densification of leveling lines, thereby reducing the project cost substantially.
Journal of Surveying Engineering-asce, Aug 1, 2016
AbstractCivil engineering projects require the orthometric height of points (i.e., the height of ... more AbstractCivil engineering projects require the orthometric height of points (i.e., the height of points above geoid). Thus, to make use of the Global Navigation Satellite System (GNSS) in engineering surveying, geoid undulation (i.e., the separation between an ellipsoid and geoid surface) must be known. In this study, an attempt has been made to determine the geoid undulation using the astro-geodetic method. Observations were taken in a network of seven stations spread over 300 km2 around Dehra Dun, India. Astronomical observations of seven stars belonging to different constellations were taken with a theodolite having a least count of 1.0 s. Global positioning system (GPS) observations were taken using dual-frequency geodetic GPS receivers with a 0.1-mm-accurate digital level. Values of astro-geodetic geoid undulations (of stations) have been found close to that computed from field levelling. Further, the values have been compared with those obtained from global geoid models such as EIGEN6C3stat and EGM2...
observations and topography information for development of geoid models (yildiz et al. 2012). The... more observations and topography information for development of geoid models (yildiz et al. 2012). The reliability of the gravimetric models, in terms of spatial resolution and accuracy, has been found to be improved by combining models with geoid undulations from GPS data/field levelling (Smith, Milbert 1999). Based on this, jGEOID 2000, a gravimetric geoid model of japan, has been updated with the geoid undulations from a network of GPS Bench Marks (B.Ms) spread over japan. It yielded to a new hybrid geoid model GSIGEOID2000, which during evaluation provided a precision (standard error) of the order of 4 cm throughout the whole of japan (Kuroishi et al. 2002). GEOID09, a hybrid geoid height model, developed by the National Geodetic Survey (NGS) US using US Gravimetric Geoid 2009 (USGG2009) gravity model along with GPS and field levelling data. An evaluation UDK 528.21
Site specific geoid model is prerequisite for accurate determination of orthometric heights. No g... more Site specific geoid model is prerequisite for accurate determination of orthometric heights. No geoid model has been developed so far for India or any of its part. So, development of a geoid model for India or its part is of utmost need to make use of GNSS data towards determination of orthometric heights. In this research work, an attempt has been made to develop geoid undulation models by gravimetric method using Molodensky’s concept. Component parameters in line with the Remove – Compute – Restore (RCR) technique have been used recursively. Models have been developed for two study areas: one of these lies in and around Dehradun (30° 19′ N, 75° 04′E) in Uttarakhand state, India in lower Himalayan region having highly undulating topography and the other near Hyderabad (17° 30′N, 78°30′E) in Telengana state of India having gentle topography. The model has been tested for 7 stations in the first study area and accuracy has been found to be 17.5 cm; whereas, for the second area accura...
Journal of The Institution of Engineers (India): Series A, 2017
Engineering projects require orthometric heights of points where as Global Navigation Satellite S... more Engineering projects require orthometric heights of points where as Global Navigation Satellite System (GNSS) provide height above ellipsoid. Thus, to make use of GNSS in engineering surveying, the relationship between ellipsoidal height and orthometric height as a function of position needs to be established through geoid modeling. In this study, an attempt has been made to develop a geoid model using the geometric method. Observations were taken in a network of sixteen stations spread over 600 km 2 around Dehra Dun, India. GPS observations were taken using dual frequency geodetic GPS receivers and leveling done using digital levels with 0.1 mm accuracy. Orthometric height of stations from developed model have been found to be near to those from field levelling which is considered most accurate. Further, the values have been compared with those obtained from the recent GOCE-GRACE-LAGEOS geoid model EIGEN6C3stat. It has been found that the geometric model provides far better accuracy than that obtained from the global geoid model. Therefore, it can be concluded that the geometric method of geoid modeling can better be used for reduction of GPS observed ellipsoidal height to orthometric height in a local area. This model may gainfully be employed in a project area as a substitute for densification of leveling lines, thereby reducing the project cost substantially.
AbstractCivil engineering projects require the orthometric height of points (i.e., the height of ... more AbstractCivil engineering projects require the orthometric height of points (i.e., the height of points above geoid). Thus, to make use of the Global Navigation Satellite System (GNSS) in engineering surveying, geoid undulation (i.e., the separation between an ellipsoid and geoid surface) must be known. In this study, an attempt has been made to determine the geoid undulation using the astro-geodetic method. Observations were taken in a network of seven stations spread over 300 km2 around Dehra Dun, India. Astronomical observations of seven stars belonging to different constellations were taken with a theodolite having a least count of 1.0 s. Global positioning system (GPS) observations were taken using dual-frequency geodetic GPS receivers with a 0.1-mm-accurate digital level. Values of astro-geodetic geoid undulations (of stations) have been found close to that computed from field levelling. Further, the values have been compared with those obtained from global geoid models such as EIGEN6C3stat and EGM2...
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