According to the characteristics of gravity passive navigation, this paper presents a novel gravity passive navigation system （GPNS）, which consists of the rate azimuth platform （RAP）, gravity sensor, digitally st...According to the characteristics of gravity passive navigation, this paper presents a novel gravity passive navigation system （GPNS）, which consists of the rate azimuth platform （RAP）, gravity sensor, digitally stored gravity maps, depth sensor and relative log. The algorithm of rate azimuth platform inertial navigation system, error state-space equations, measurement equations and GPNS optimal filter are described. In view of the measurements made by an onboard gravity sensor the Eotvos effect is introduced in the gravity measurement equation of a GPNS optimal filter. A GPNS is studied with the Matlab/Simulink tools; simulation results demonstrate that a GPNS has small errors in platform attitude and position. Because the inertial navigation platform is the rate azimuth platform in the GPNS and gravity sensor is mounted on the rate azimuth platform, the cost of the GPNS is lower than existing GPNS＇s and according to the above results the GPNS meets the need to maintain accuracy navigation for underwater vehicles over long intervals.展开更多
This paper summarizes the main instrumental and methodological points of the tidal research which was performed in the framework of the National Scientific Research Fund Project K101603. Since the project is still run...This paper summarizes the main instrumental and methodological points of the tidal research which was performed in the framework of the National Scientific Research Fund Project K101603. Since the project is still running the tidal analysis results published here are only preliminary. Unmodelled tidal effects have been highlighted in some recent absolute gravity measurements carried out in the Pannonian basin resulting in a periodic modulation exceeding the typical standard deviations （±1microGal） of the drop sets. Since the most dominant source of the daily gravity variation is the bulk tidal effect, the goal of the project is to check its location dependency at BGal level. Unfortunately Hungary has had no dedicated instrumentation, so an effort was made to make the available LaCoste- Romberg spring G meters capable for continuous recording. As a reference instrument the GWR SG025 operated in the Conrad Observatory, Austria was also used and in the mean time of the project, a Scintrex CG-5 became also available, Eventually 6 instruments at 5 different locations were operated for 3 9 months mainly in co-located configuration. Although many experiments （moving mass calibrations） were done to determine the scale factors and scale functions of the instruments, the direct comparison of the tidal parameters obtained from the observations is still questionable. Therefore the ratio of the delta factors of O1 and M2 tidal constituents was investigated supposing that M2 is much more influenced by the ocean loading effect than O1. The slight detected increase of δ（O1 ）/δ（M2） （≈0.2%） toward east does not contradict to theory. This result has to be validated in the near future by analyzing available ocean loading models.展开更多
Understanding the location of the subsurface heat sources is crucial for efficient geothermal resource exploration and exploitation. This study aimed to investigate the faults and the depth to heat sources for a geoth...Understanding the location of the subsurface heat sources is crucial for efficient geothermal resource exploration and exploitation. This study aimed to investigate the faults and the depth to heat sources for a geothermal system in Magadi, southern Rift Valley, through the integration of gravity mapping, 3D Euler deconvolution, and spectral analysis. Gravity mapping is a powerful geophysical method widely used to infer subsurface density variations, which are indicative of geological structures and volcanic intrusions that can be potential heat sources. The Volcano-Tectonic and Fluvial-Deltaic Sedimentation process of the Kenyan rift which encompasses the Magadi basin are responsible for geomorphic and geologic processes in the area. Alkali lava sheets of Magadi plateau trachytes covered with lacustrine sediments characterize 80% of the area. Deeper is the Tanzanian craton basement, overlain by Pliocene to Miocene volcanic and sedimentary rocks. A gravity survey with a data density of 2.375 stations/km<sup>2</sup> produced high-resolution anomaly and total horizontal derivative maps showing gravity highs between −180 mGals to −174 mGals along the eastern zone of the study area. A buried major fault trending N-S was delineated in the mid-upper region of the area by Euler solutions at an average depth of 350 meters. Deeper features associated with possible volcanic dykes and sills gave Euler depth ranges of 0.7 km to 2.2 km. Radial average spectral analysis showed depth to the top of shallow and deep features at 2.4694 km and 5.827 km respectively. The correlation between gravity anomalies, geological structures, and present hot springs supports the hypothesis that volcanic processes have played a significant role in the development of the geothermal system in the study area.展开更多
文摘According to the characteristics of gravity passive navigation, this paper presents a novel gravity passive navigation system （GPNS）, which consists of the rate azimuth platform （RAP）, gravity sensor, digitally stored gravity maps, depth sensor and relative log. The algorithm of rate azimuth platform inertial navigation system, error state-space equations, measurement equations and GPNS optimal filter are described. In view of the measurements made by an onboard gravity sensor the Eotvos effect is introduced in the gravity measurement equation of a GPNS optimal filter. A GPNS is studied with the Matlab/Simulink tools; simulation results demonstrate that a GPNS has small errors in platform attitude and position. Because the inertial navigation platform is the rate azimuth platform in the GPNS and gravity sensor is mounted on the rate azimuth platform, the cost of the GPNS is lower than existing GPNS＇s and according to the above results the GPNS meets the need to maintain accuracy navigation for underwater vehicles over long intervals.
基金the financial support of NKFIH-OTKA in the framework of contract K101603
文摘This paper summarizes the main instrumental and methodological points of the tidal research which was performed in the framework of the National Scientific Research Fund Project K101603. Since the project is still running the tidal analysis results published here are only preliminary. Unmodelled tidal effects have been highlighted in some recent absolute gravity measurements carried out in the Pannonian basin resulting in a periodic modulation exceeding the typical standard deviations （±1microGal） of the drop sets. Since the most dominant source of the daily gravity variation is the bulk tidal effect, the goal of the project is to check its location dependency at BGal level. Unfortunately Hungary has had no dedicated instrumentation, so an effort was made to make the available LaCoste- Romberg spring G meters capable for continuous recording. As a reference instrument the GWR SG025 operated in the Conrad Observatory, Austria was also used and in the mean time of the project, a Scintrex CG-5 became also available, Eventually 6 instruments at 5 different locations were operated for 3 9 months mainly in co-located configuration. Although many experiments （moving mass calibrations） were done to determine the scale factors and scale functions of the instruments, the direct comparison of the tidal parameters obtained from the observations is still questionable. Therefore the ratio of the delta factors of O1 and M2 tidal constituents was investigated supposing that M2 is much more influenced by the ocean loading effect than O1. The slight detected increase of δ（O1 ）/δ（M2） （≈0.2%） toward east does not contradict to theory. This result has to be validated in the near future by analyzing available ocean loading models.
文摘Understanding the location of the subsurface heat sources is crucial for efficient geothermal resource exploration and exploitation. This study aimed to investigate the faults and the depth to heat sources for a geothermal system in Magadi, southern Rift Valley, through the integration of gravity mapping, 3D Euler deconvolution, and spectral analysis. Gravity mapping is a powerful geophysical method widely used to infer subsurface density variations, which are indicative of geological structures and volcanic intrusions that can be potential heat sources. The Volcano-Tectonic and Fluvial-Deltaic Sedimentation process of the Kenyan rift which encompasses the Magadi basin are responsible for geomorphic and geologic processes in the area. Alkali lava sheets of Magadi plateau trachytes covered with lacustrine sediments characterize 80% of the area. Deeper is the Tanzanian craton basement, overlain by Pliocene to Miocene volcanic and sedimentary rocks. A gravity survey with a data density of 2.375 stations/km<sup>2</sup> produced high-resolution anomaly and total horizontal derivative maps showing gravity highs between −180 mGals to −174 mGals along the eastern zone of the study area. A buried major fault trending N-S was delineated in the mid-upper region of the area by Euler solutions at an average depth of 350 meters. Deeper features associated with possible volcanic dykes and sills gave Euler depth ranges of 0.7 km to 2.2 km. Radial average spectral analysis showed depth to the top of shallow and deep features at 2.4694 km and 5.827 km respectively. The correlation between gravity anomalies, geological structures, and present hot springs supports the hypothesis that volcanic processes have played a significant role in the development of the geothermal system in the study area.
