THE EFFECT OF GRAVITY MEASUREMENT DISTRIBUTION POINTS ON INTERPRETATION OF GRAVITY DATA IN THE GUNUNG ENDUT GEOTHERMAL PROSPECT AREA, INDONESIA

Supriyanto Supriyanto

doi:10.21660/2018.41.07022

Analysis of the Dynamic Height Distribution at the Estuary of the Odra River Based on Gravimetric Measurements Acquired with the Use of a Light Survey Boat—A Case Study

Sensors ◽

10.3390/s20216044 ◽

2020 ◽

Vol 20 (21) ◽

pp. 6044

Author(s):

Krzysztof Pyrchla ◽

Arkadiusz Tomczak ◽

Grzegorz Zaniewicz ◽

Jerzy Pyrchla ◽

Paulina Kowalska

Keyword(s):

Data Stream ◽

Gravity Data ◽

Gravity Measurement ◽

Reference Level ◽

Height Distribution ◽

Dynamic Height ◽

Area Of Interest ◽

Gravimetric Measurements ◽

Accuracy Of Measurements ◽

Odra River

This article presents possible applications of a dynamic gravity meter (MGS-6, Micro-g LaCoste) for determining the dynamic height along the Odra River, in northwest Poland. The gravity measurement campaign described in this article was conducted on a small, hybrid-powered survey vessel (overall length: 9.5 m). We discuss a method for processing the results of gravimetric measurements performed on a mobile platform affected by strong external disturbances. Because measurement noise in most cases consists of signals caused by non-ideal observation conditions, careful attempts were made to analyze and eliminate the noise. Two different data processing strategies were implemented, one for a 20 Hz gravity data stream and another for a 1 Hz data stream. A comparison of the achieved results is presented. A height reference level, consistent for the entire estuary, is critical for the construction of a safe waterway system, including 3D navigation with the dynamic estimation of under-keel clearance on the Odra and other Polish rivers. The campaign was conducted in an area where the accuracy of measurements (levelling and gravimetric) is of key importance for shipping safety. The shores in the presented area of interest are swampy, so watercraft-based measurements are preferred. The method described in the article can be successfully applied to measurements in all near-zero-depth areas.

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High-resolution gravity measurement aboard an autonomous underwater vehicle

Geophysics ◽

10.1190/geo2018-0090.1 ◽

2018 ◽

Vol 83 (6) ◽

pp. G119-G135 ◽

Cited By ~ 4

Author(s):

Takemi Ishihara ◽

Masanao Shinohara ◽

Hiromi Fujimoto ◽

Toshihiko Kanazawa ◽

Akito Araya ◽

...

Keyword(s):

High Resolution ◽

Autonomous Underwater Vehicle ◽

Gravity Data ◽

Water Pressure ◽

Bouguer Anomaly ◽

Underwater Vehicle ◽

Mineral Deposits ◽

Gravity Measurement ◽

Vertical Acceleration ◽

Constant Depth

We have developed an underwater gravity measurement system that uses an autonomous underwater vehicle (AUV) for exploration of seafloor mineral deposits. An improved air/sea gravimeter mounted on a gimbal mechanism in a pressure capsule 50 cm in diameter was installed in the AUV Urashima. We carried out 11 AUV dives in Sagami Bay as well as in deep-sea mineral deposit areas offshore Japan. The AUV was navigated at a constant speed of 2 knots and at either constant depth or constant altitude above the sea bottom. We obtained high-resolution Bouguer anomaly data through processing of gravity data, water pressure data, and the AUV’s navigational data, including pitch and roll motion. In addition to a vertical acceleration correction using a precise pressure meter with an in situ conversion factor from pressure to depth, three additional corrections were made to the gravimeter data: corrections for the effects of a spatial separation and a time delay between the depth sensor and the gravimeter, and an adjustment to the conversion from pressure increments to depth increments. These new corrections allowed us to obtain high-resolution data in a constant-depth survey of the southern Izena Hole at a depth of approximately 1550 m. The data had a 0.1 mGal rms crossover difference after leveling. This survey revealed two high Bouguer anomaly areas with amplitudes of 1–2 mGal. A model calculation suggested that the anomalies result from the presence of two buried cylindrical high-density mineral deposits. Our data processing method allows the detection of mineral deposits located at or just beneath the seafloor using gravity data collected aboard AUVs. However, further improvements in resolution are desirable, particularly for surveys in areas with rugged topography.

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Determination of Vertical Deflection Based on Terestrial Gravity Disturbance Data (A Case Study in Semarang City)

KnE Engineering ◽

10.18502/keg.v4i3.5834 ◽

2019 ◽

Author(s):

L M Sabri ◽

Bambang Sudarsono ◽

Rina Dwi Indriana

Keyword(s):

Gravity Anomaly ◽

Gravity Data ◽

Satellite System ◽

Gravity Measurement ◽

Gravity Disturbance ◽

Vertical Deflection ◽

Level Measurement ◽

Vening Meinesz ◽

Global Navigation Satellite ◽

New Formula

Vertical deflection can be determined by geometrical and physical measurement. In geometrical way, vertical deflection is obtained by comparing astronomical coordinate and geodetical coordinate. In physical way, vertical deflection can be computed from gravity measurement. In the past, vertical deflection was computed from gravity anomaly data. Gravity anomaly data measurement is difficult because it need reduction of gravity from surface of the earth to the geoid using orthometric height from spirit level measurement. In modern era, gravity anomaly data may be replaced by gravity disturbance data whose only required gravity and GNSS (Global Navigation Satellite System) measurement. This research aims to determine vertical deflection in Semarang City from terrestrial gravity disturbance data. The gravity data were measured in March of 2016. Formula of Vening Meinesz that usually used for vertical deflection was replaced by new formula that generated from derivation of function of Hotine. Applying gravity disturbance gave vertical deflection of east-west component that were vary from -1.2” to 12.2” while north-south component were vary from -4.2” to 4.2”. Comparing vertical deflection as computed from terrestrial data to as computed from EGM2008 coefficients showed conformity in shape and values. It was concluded that derivation of function of Hotine could be applied for vertical deflection determination from gravity disturbance.

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