Relative Gravimeters Research Articles

Simultaneous calibration of instrument scale factor and drift rate in network adjustment for continental-scale gravity survey campaign

SUMMARY The scale factor of each relative gravimeter must be calibrated both before and after the fieldwork of a terrestrial gravity survey, to reduce uncertainties and ensure high precision. Conventionally, such calibration is a time-consuming process performed following well-established baselines. We propose a new Bayesian method to estimate the scale factor in a hybrid gravity network that includes several absolute gravity observation stations. In this approach, the scale factor is estimated as a hyperparameter using the Akaike Bayesian information criterion and using known absolute gravity stations in the network or/and calibrated instruments as constraints. Testing the sensitivity of the gravity values and the residuals of the gravity difference between two successive stations to the change of the scale factor demonstrates the robustness of this method. We also test the sensitivity of the estimated scale factor in the presence of Gaussian noise and the non-linear instrumental drift rate. Moreover, if the maximum absolute gravity interval is greater than 60 per cent of the range of gravity values in the network, or if the known scale factors of calibrated gravimeters are well calibrated, this approach can provide reasonable estimates of the daily drift rate and the unknown scale factors, where the latter has an error of <3 × 10−5. We apply this approach to real gravity campaign data from Yunnan in China and use a cross-validation method to compare estimated gravity values and corresponding gravity values obtained from absolute gravity observations at the same stations, to validate how the proposed method improves estimation accuracy of the gravity value at each station.

Gravity observation of field camp geophysics in Karangsambung using Data Acquisition 2005-2019

The study of field camp geophysics in Karangsambung has been done since 1996 until 2019 by geophysical engineering ITB. During the field activities, students was assigned with several data acquisition using various geophysical methods. One of the most common method to conducted alongside with surface geological mapping is gravity. Compilation of gravity data during the activities will be presented in this work. There are two categories of data compilation during 24 years: data compilation 1996-2004, and 2005-2019. The observation conducted using relative gravimeter with data distribution already cover geological surface map in the study area (Luk-Ulo Melange Complex, Karangsambung Formation, Totogan Formation, and Diabas Intrusion). The pattern of gravity observation shows correlated with topographic variation. Range gravity observation from this study is about 62 mGal.

Gravity observations at Jang Bogo Station, Antarctica, and scale factor calibrations of different relative gravimeters

We conducted gravity observations in Antarctica at Jang Bogo Station (JBS) during the 2019–2020 Austral summer season using an FG5-210 absolute gravimeter (AG) and a LaCoste & Romberg (LCR) Model D-58 relative gravimeter. Absolute gravity measurements were successfully made at reference gravity point JBSAG1 and newly established gravity point JBSAG2, yielding about 19,000 and 14,400 drops of data, respectively, with measurement precisions better than 0.4 μGal (1 μGal = 10−8 m s−2). In addition, relative gravity measurements were conducted at 10 other newly established gravity points, with accuracies better than 10 μGal, to supplement the absolute gravity data. Superconducting gravimeter (SG) observation with an iGrav-021 instrument has been underway at JBS since 2016. Since an SG is a relative gravimeter, the calibration of the scale factor is essential for long-term gravity monitoring. In addition, the D-58 instrument was required for scale factor calibration. To calibrate the scale factors of these gravimeters, we first estimated a value for the iGrav-021 using parallel observations with the FG5-210 instrument. The D-58 scale factor was then estimated indirectly from parallel observations with the iGrav-021. These calibrations should ensure accurate gravity monitoring in future work.

Bayesian estimation of scale factor for CG-5 relative gravimeter

The terrestrial time-variable microgravity survey is an important means to monitor geodynamic processes underground. The Scintrex CG-5 relative gravimeter, which is the mainstream instrument for terrestrial relative gravity measurement at present, its scale factor (SF) is an important factor affecting the quality of the observation data. Unlike the conventional gravity adjustment procedure, this study takes account of the nonlinear drift rate of the CG-5 gravimeter, depending on the known absolute gravity (AG) in the network, and the scale factor is considered as one of the hyper-parameters to be estimated by means of Akaike’s Bayesian information Criterion (ABIC). In order to quantify the errors caused by the bias of scale factor, we applied this new approach to process actual gravity survey campaign data in Yunnan gravity network from 2018 to 2020, then analyzed the residuals of gravity differences (GD) between station pairs and the difference of GD between two relative gravimeters (CG5 #1169 and CG5 #1170). The cross-validation of the absolute gravity (AG) from the quasi-synchronous observation in the network is also used in the paper. It has shown that this new approach is effective to improve the accuracy of scale factor and adjustment results.

The Grid Optimization of The Terrestrial Gravity Survey (Case Study: Central Part of Java Island)

BIG has conducted gravity data by using several methods, namely terrestrial gravity and airborne gravity to produce high accuracy of the geoid. The terrestrial gravity survey was carried out using the grid method, and BIG does not have any guidance on the size of the used grid interval size. We try to divide the grid interval into four different sizes of grids, those are km, 10 km, 15 km, and 20 km. A case study in the central part of Java Island, at Semarang and Yogyakarta in 2019, using Scintrex CG-5 relative terrestrial gravimeter equipment. By using the integral stokes and Least Square Collocation (LSC) approaches, the gravimetric geoid is obtained from each grid interval. We compared gravimetric geoid with geometric geoid on 179 vertical benchmarks and obtained the results of the 5 km grid interval having the smallest average value of 0.273 meters ± 0.310 with the most appropriate conformity test.

CO2 storage monitoring using 3-axis borehole gravity

Carbon capture and storage underground (CCS) is now regarded as a vital and significant means to achieve 3 of the 4 IPCC pathways necessary to limit global warming to 1.5degC. Our internal analysis indicates the number of wells required to facilitate the levels of CO2 capture to meet these objectives are numerous over the next 30 years. An understanding of containment is essential for CO2 storage, but few options exist to monitor a CO2 plume growth 100's of metres away from a well. Gravity is a direct measurement of density, through substitution of water by CO2. The gravity measurement detects changes in mass in the subsurface, such that time-lapse wireline-based surveys may be taken to build up a picture of fluid movements at 100’s of meters from the wellbore. By measuring gravity in all three-axis it is possible to determine directional information about the spatial movement of fluid, even when acquired from just a single borehole. We present emerging 3-axis borehole gravity technology that enables the recording of gravitational acceleration at very high sensitivity (targeted at ≈ 5 µGal) using an innovation in resonant Microelectromechanical system (MEMS) vibrating beam technology with the aim of making small, cheap, but highly stable and highly sensitive field and borehole-deployable relative gravimeters. The vibrating beam gravimeter consists of a suspended mass connected to a vibrating beam, such that the inertial force experienced by the mass in gravitational field is communicated as an axial load on the beam. The technology is currently undergoing field trials as part of the CCP* and we show the results of a feasibility study aimed at monitoring CO2 in a deep storage reservoir in Canada which shows the gravity variation likely to be seen due to density changes during a period of CO2 injection. The displacement and substitution of the aquifer water at the storage site over time is referred to as a 4D gravity survey. The cost effectiveness of a 4D wireline gravity survey compared to 4D seismic survey is highly attractive in smaller carbon storage programs. Where the project size or complexity allow both to be run, the complementary nature of the measurements has been noted by several operators. Survey feasibility modelling and a workflow are presented that together provide important information for planning and acquiring a successful gravity survey, as well as the best time interval (given the planned injection rate), and which well location is most suitable to use. The workflow for conducting borehole gravity simulations from time-lapse reservoir models starts with a 3D model of reservoir porosity, saturation and fluid constituent density, which is used to generate a time-lapse density model from the provided set of reservoir simulation data. Vector gravity anomaly responses (gz, gx, and gy) along the wellbore in a variety of well locations are then predicted through forward modelling. The density changes due to fluid substitution are measured by the vertical, gz, gravity anomaly with respect to the reference gravity field. The fluid front progress through the field is assessed through the horizontal gravity anomalies (gx, and gy). Modelling shows plume growth is detectable even over a period of 1 year (Figure 1) and with MEMS technology lifetime monitoring is possible. We conclude that this emerging technology has the potential to provide a solution for long term monitoring of CO2 plume growth within the likely numerous wells that may be needed to fill the CO2 storage requirements resulting from the IPCC pathway scenarios to 1.5degC.

First evaluation of an absolute quantum gravimeter (AQG#B01) for future field experiments

Abstract. Quantum gravimeters are a promising new development allowing for continuous absolute gravity monitoring while remaining user-friendly and transportable. In this study, we present experiments carried out to assess the capacity of the AQG#B01 in view of future deployment as a field gravimeter for hydrogeophysical applications. The AQG#B01 is the field version follow-up of the AQG#A01 portable absolute quantum gravimeter developed by the French quantum sensor company Muquans. We assess the instrument's performance in terms of stability (absence of instrumental drift) and sensitivity in relation to other gravimeters. No significant instrumental drift was observed over several weeks of measurement. We discuss the observations concerning the accuracy of the AQG#B01 in comparison with a state-of-the-art absolute gravimeter (Micro-g-LaCoste, FG5#228). We report the repeatability to be better than 50 nm s−2. This study furthermore investigates whether changes in instrument tilt and external temperature and a combination of both, which are likely to occur during field campaigns, influence the measurement of gravitational attraction. We repeatedly tested external temperatures between 20 and 30 ∘C and did not find any significant effect. As an example of a geophysical signal, a 100 nm s−2 gravity change is detected with the AQG#B01 after a rainfall event at the Larzac geodetic observatory (southern France). The data agreed with the gravity changes measured with a superconducting relative gravimeter (GWR, iGrav#002) and the expected gravity change simulated as an infinite Bouguer slab approximation. We report 2 weeks of stable operation under semi-terrain conditions in a garage without temperature-control. We close with operational recommendations for potential users and discuss specific possible future field applications. While not claiming completeness, we nevertheless present the first characterization of a quantum gravimeter carried out by future users. Selected criteria for the assessment of its suitability in field applications have been investigated and are complemented with a discussion of further necessary experiments.

Gravity field modelling for the Hannover 10 m atom interferometer

Absolute gravimeters are used in geodesy, geophysics and physics for a wide spectrum of applications. Stable gravimetric measurements over timescales from several days to decades are required to provide relevant insight into geophysical processes. Users of absolute gravimeters participate in comparisons with a metrological reference in order to monitor the temporal stability of the instruments and determine the bias to that reference. However, since no measurement standard of higher-order accuracy currently exists, users of absolute gravimeters participate in key comparisons led by the International Committee for Weights and Measures. These comparisons provide the reference values of highest accuracy compared to the calibration against a single gravimeter operated at a metrological institute. The construction of stationary, large-scale atom interferometers paves the way for a new measurement standard in absolute gravimetry used as a reference with a potential stability up to 1,hbox {nm}{/}{hbox {s}^{2}} at 1 s integration time. At the Leibniz University Hannover, we are currently building such a very long baseline atom interferometer with a 10-m-long interaction zone. The knowledge of local gravity and its gradient along and around the baseline is required to establish the instrument’s uncertainty budget and enable transfers of gravimetric measurements to nearby devices for comparison and calibration purposes. We therefore established a control network for relative gravimeters and repeatedly measured its connections during the construction of the atom interferometer. We additionally developed a 3D model of the host building to investigate the self-attraction effect and studied the impact of mass changes due to groundwater hydrology on the gravity field around the reference instrument. The gravitational effect from the building 3D model is in excellent agreement with the latest gravimetric measurement campaign which opens the possibility to transfer gravity values with an uncertainty below the {10},hbox {nm}{/}{hbox {s}^{2}} level.

The NEWTON-g Gravity Imager: Toward New Paradigms for Terrain Gravimetry

Knowledge of the spatio-temporal changes in the characteristics and distribution of subsurface fluids is key to properly addressing important societal issues, including: sustainable management of energy resources (e.g., hydrocarbons and geothermal energy), management of water resources, and assessment of hazard (e.g., volcanic eruptions). Gravimetry is highly attractive because it can detect changes in subsurface mass, thus providing a window into processes that involve deep fluids. However, high cost and operating features associated with current instrumentation seriously limits the practical field use of this geophysical method. The NEWTON-g project proposes a radical change of paradigm for gravimetry through the development of a field-compatible measuring system (the gravity imager), able to real-time monitor the evolution of the subsurface mass changes. This system includes an array of low-costs microelectromechanical systems-based relative gravimeters, anchored on an absolute quantum gravimeter. It will provide imaging of gravity changes, associated with variations in subsurface fluid properties, with unparalleled spatio-temporal resolution. During the final ∼2 years of NEWTON-g, the gravity imager will be field tested in the summit of Mt. Etna volcano (Italy), where frequent gravity fluctuations, easy access to the active structures and the presence of a multiparameter monitoring system (including traditional gravimeters) ensure an excellent natural laboratory for testing the new tools. Insights from the gravity imager will be used to i) improve our knowledge of the cause-effect relationships between volcanic processes and gravity changes observable at the surface and ii) develop strategies to best incorporate the gravity data into hazards assessments and mitigation plans. A successful implementation of NEWTON-g will open new doors for geophysical exploration.

Impact of environmental phenomena on continuous relative gravity measurements performed in urban area

The relative monitoring gravimeter gPhoneX #108 was installed in the building of Faculty of Civil Engineering of the Slovak University of Technology in Bratislava in the beginning of 2016. Main purpose of the paper is to analyze how external environmental phenomena generating non-gravitational signal, such as strong human activity, ambient noise and tilting of observing site due to solar radiation, can influence the quality of relative gravity measurements and their suitability for geodynamic applications. For this purpose, we accomplished spectral analysis of gravity data with different sampling rate, examination of instrumental drift, and tidal analysis of hourly gravity records. Our study showed that the gPhoneX #108 gravity measurements are adversely affected by the tilting of the building, where the gravimeter is located. This effect produces a significant non gravitational signal with characteristic daily and seasonal variation depending on the weather conditions. The instability of the observing site also generates a strong non-gravitational signal and corrupts the estimation of tidal parameters mainly in a diurnal tidal band. The investigation of the instrumental drift proved its irregular character due to the changes of temperature in the operating room. Another limitation factor for detection of small gravity changes is the level of ambient noise with the average daily amplitude of about 100 nm s−2. Obtained experimental results can be useful for planning and performing the relative gravity measurements in a noisy environment, or in the case of an instable observing site. The most significant non-gravitational signal with variable daily and seasonal influence was caused by the instability of the observing site. In order to minimize this influence we recommend regular calibration of the built-in tiltmeters.

Upper mantle density and surface gravity change in Fennoscandia, determined from GRACE monthly data

Precise gravity measurements have been repeatedly observed in Fennoscandia since the 1960-ties, first by relative gravimeters, then by absolute gravimeters, for studying the temporal change of gravity related with the on-going glacial isostatic adjustment (GIA). The results of such studies are vital for understanding GIA processes and tuning GIA and Earth structure models.This study uses monthly repeated data from the twin satellite mission GRACE for 164 months between 2003 and 2016 for estimating the temporal change of surface gravity, its ratio (f) to the land uplift rate as well as the upper mantle density related with the viscous mass flow in the mantle. The maximum negative change of gravity is estimated to −1.8 μGal/yr, and f is estimated to −0.172 ± 0.018 μGal/mm.The solutions for f from the three independent techniques (relative, absolute and satellite gravity observations) were found to agree statistically without significant biases, and they were merged in a joint solution to −0.166 ± 0.004 μGal/mm, corresponding to a mean upper mantle mass flow density of 3402.5 ± 95 kg/m3, which decreases towards the uplift center.

Research on Iterative Calibration Method of Linear Model Parameters of Gravity Sensor

In recent years, the calibration method of Strapdown gravimeter has become the bottleneck of relative gravity measurement accuracy. Based on this situation, this thesis studies the parameter iterative calibration method of SGA-WZ03 strapdown gravimeter to break the bottleneck of relative gravity measurement and further improve the measurement accuracy of relative gravimeter in flight experiment through the improvement of calibration method Degree. The parameter iterative estimation algorithm is based on the pulse output model of a single accelerometer to establish the linear pulse output model of the accelerometer components. Using the idea of parameter separation, the two-step iterative estimation of the model parameters and the tilt vector can complete the calibration of the linear model and the secondary model of the accelerometer. Compared with the traditional 24 bit calibration method, the parameter estimation iterative estimation calibration method has better stability than the traditional method.

Practical Experiences with the First Relative Gravimeter of Type Scintrex CG-6 Autograv in Dubai, The United Arab of Emirates

In September 2019, the Dubai Municipality of Dubai Emirate, the United Arab of Emirates, has received its first Scintrex CG-6 Autograv gravity meter. This paper describes the installation and initial gravity signals with the new CG-6 Autograv gravimeter. Two gravity field sites have been selected in Dubai City and Hatta mountainous area. The relative gravity field measurements have been recorded for about one month time span; two weeks in Dubai and two weeks in Hatta. Among different effects reducing the gravity measurements, the tide and drift corrections have been focused on this paper. Two tidal models have been applied to reduce the tide effect based on the automated ETGTAB of the CG-6 gravimeter and ETERNA3.3 software. The results regarding the tide correction show very small discrepancies between both models (ETGTAB and ETERNA3.3) of about 2.2 μGal and 2.6 μGal in terms of standard deviations at Dubai and Hatta gravity stations, respectively. So, the outcome of the precise tidal model of CG-6 Autograv gravimeter is reliable for tidal reduction within Dubai area and its surroundings. Regarding the drift correction, the CG-6 Autograv provides low instrument drift values about 2.44 μGal and -2.35 μGal per day for the Dubai and Hatta stations, respectively. Furthermore, it is recommended that the Hatta gravity station would be considered as a stable and trusted gravity site. For Dubai gravity station, the gravity observations are affected by some noises from traffic activities while recording the gravity signal during the working days. Therefore, it is recommended for Dubai gravity station to be measured during the weekends and at nights in order to avoid any noises affecting the CG-6 gravimeter.

Long‐Term Stability of Tilt‐Controlled gPhoneX Gravimeters

AbstractSpring relative gravimeters are considered too unstable to provide useful information on long‐term gravity variations. In this paper, we prove that the new generation of spring gravimeter gPhoneX can reach long‐term stability at the μGal level (10 nm s−2) when the verticality of the gravimeter is maintained, if the instrumental drift can be correctly estimated. We conducted two comparisons with different gPhoneXs in different observatories and environmental conditions. In the “Walferdange Underground Laboratory for Geodynamics” in Luxembourg, we compared time series from the gPhoneX (with and without tilt control), with data from a superconducting gravimeter. We found an agreement at the μGal level when the tilt control is switched on. We validated this result by repeating the experiment at the “Geodesy in Karstic Environment” observatory in the south of France. The fit between the superconducting gravimeter and the gPhoneX hourly values gives similar results at all frequencies over 276 days of measurements. The linear correlation coefficient between the gPhoneX and superconducting gravimeter reaches 0.99, with a misfit of 6.0 nm s−2. We demonstrated that tilt‐controlled gPhoneXs are suitable for long‐term gravity monitoring.

A combined EMD and MSSA model for the extraction of gravity tide correction from relative gravimetric data

A combined empirical mode decomposition (EMD) and multichannel singular spectrum analysis (MSSA) model (EMD–MSSA model) was used for extraction of the gravity tide correction without a priori information (e.g., station coordinates) from static relative gravimetric data. Static observational data acquired using a CG-5 relative gravimeter over 16 days were used to investigate the feasibility and reliability of the proposed method. The singular spectrum analysis (SSA) method and empirical mode decomposition (EMD)–independent component analysis (ICA) method were also adopted for comparison. Experimental results show that the time series of the gravity tide correction estimated using EMD–MSSA, SSA and EMD–ICA methods are consistent with a theoretical reference (the Longman formula). The gravity tide correction estimated using the EMD–MSSA method is closer to the theoretical model than other methods, the root-mean-square difference of the residuals between estimated values and theoretical values are smallest, and the accuracy of the gravity tide correction time series derived using the EMD–MSSA method is thus highest. The correlation coefficient of extraction results and GT is highest for the results extracted using the EMD–MSSA method. The experimental results show that using the EMD–MSSA model, which combines the advantages of the MSSA and EMD signal processing methods, improves the extraction estimation accuracy and reliability of the gravity tide correction from relative gravimetric data.

Stability of the Calibration of Scintrex Relative Gravimeters as Inferred from 12 Years of Measurements on a Large Amplitude Calibration Line in Iran

In spite of the large stability of the fused quartz elastic system, which is utilized in modern relative gravimeters such as Scintrex CG-5, precise gravity measurements need regular calibration mostly because of weak changes in time of the elastic properties of the spring. Calibration of the relative gravimeters is important to avoid the systematic error of scale in relevant observations. In this study, due to the establishment of a large amplitude (of about 1200 mGal) calibration line in Iran, the stability of three CG-3 M and three CG-5 gravimeters has been continuously investigated based on the results of a 12 year (2005–2017) observations. The absolute gravity values at calibration stations were measured during the period 2005–2007 and more recently in 2017–2018 (for most of the stations) with absolute FG5 gravimeters. The results show that the Scintrex gravimeters exhibit different behaviors on the calibration line. The accuracy of determining the calibration coefficient of the gravimeters was better than 40 ppm. According to our results there is no effect of the gravity amplitude itself on the calibration factors. CG-5 #83 and CG-5 #87 have the largest changes in calibration factor (more than 1000 ppm) over the 12 year observation period while CG-3 M #20 and CG-3 M #60 have the smallest range (less than 200 ppm). The misclosure of relative gravity measurements in the first-order gravity network of Iran has been calculated before and after calibration corrections and it is shown that applying the scale factor correction reduced significantly the misclosures on the gravity network.

On the determination of vertical gravity gradients by corner-cube absolute gravimeters

This paper describes a new approach for the determination of vertical gravity gradients (VGGs) from the measurements of corner-cube absolute gravimeters based on laser interferometry. The new approach has been obtained by the modification of the equation for linear least squares solution used in the determination of the g-values. It enables one to establish a clear mathematical relation between the gravity residuals and the VGG estimates. As it is shown, in the determination of gradients with an accuracy approaching 10 µGal m−1 (1 µGal = 1 × 10−8 m s−2), it is necessary to correct directly the measured quantities (time and distance pairs) for ‘known’, or sufficiently well modelled, perturbations as e.g. self-attraction or cable effects. Generally, if the gradients are determined from the data of absolute gravimeters, systematic low frequency perturbation in the residuals have to be analysed carefully. In this way, hidden perturbations in the residuals can be identified, which might be important also for the correct estimation of the g-values and associated uncertainties. This is shown on the example of a parasitic wave detected in the residuals of the FG5X-251 gravimeter, reaching a period of about 0.13 m and amplitudes up to 40 pm. Finally, we compare the gravity gradients determined by the new approach with a more accurate method using relative gravimeters. This comparison shows that the gradient estimates from the FG5X-251 absolute gravimeter are biased by about 10 µGal m−1 and reach reproducibility of 14 µGal m−1. The effort to determine VGGs from absolute gravimeters enhanced the analyses of the measured data, identified still existing artefacts in the gravity residuals, the explanation of which should lead to improvements in the measurement model in order to obtain more accurate estimates of the g-values, VGGs and their uncertainties.

Processing and data analysis of time-lapse microgravity due to ground water level changing in baseline stage of CO2 injection

Monitoring stability of the field in research area using time-lapse microgravity method has been done with data acquisition process in 2014 and 2016. This method requires high accuracy in µGal units. Since we use relative gravimeter, drift performance from instrument is also influential to the data significantly. In this paper we conducted reprocessing data using closer reference station from research area thus the drift effect cause by mobilitation time and duration of instrumental resting can be reduced. In conditions prior to injection, ideally the change in gravity value in the area would be very small with the assumption of the absence of injection activity. However, after the processing data stage we can see time-lapse microgravity anomalies within the range of ± 80 µGal. This anomaly was assumed occurred by instrument effect (typical for spring sensors) in field measurement and shallow hidrology effect (ground water level change). From the gravity surveys in 2014 and 2016, there is big difference in long term drift between 2014 and 2016 data, which is 2014 has average value of 320 µGal/day and 2016 has average value of 120 µGal/day. Other than that, in repeatability test, 2014 has 54% and 2016 has 77% from total data that is within the range of deviation ± 10 µGal (repeatability value in accuracy of ideal Scintrex CG-5). Analysis of gravity data measured in three benchmark (BM) was also performed to know the gravity variation rate in research area.

Bouguer anomaly comparison using elevation data measured with hand-held device and geodetic GPS in Blora and Pandan Mountain

Land gravity measurements for subsurface studies require good accuracy for three-dimensional measurement of station’s coordinate (X, Y, Z). These coordinate data will contribute to calculation of Bouguer anomaly correction in the research area. In this study, we compared the coordinate data measured using hand-held devices and geodetic GPS devices. A more accurate tool is a Trimble R4 geodetic GPS and then we select the acquired data as a reference (Ground Control Points). The hand-held devices that we used are consist of the SUUNTO Escape 203 altimeter and the Garmin GPSMAP 60CSx. The research areas of this studi are in Blora and Pandan Mountain. At that location, we conducted acquisition of elevation data and also gravity. The relative gravimeter used to observe variations of gravity in this study is Scintrex CG5. Gravitational data processing is performed until we obtain Complete Bouguer Anomaly (CBA). The results of this study, we get statistical comparison of the accuracy of elevation data as well as differences in CBA values from the study area. Accuracy of elevation data with hand-held devices based on field measurements in Blora and Mount Pandan reaches 6-53 and 54-95 times lower than a geodetic GPS device. The Bouguer anomaly comparison of the 50 point measurements at the two sites gave the difference range of -1.03 to 2.93 mGal.

A new type of compact gravimeter for long-term absolute gravity monitoring

Long-term absolute gravity monitoring has a wide range of applications in the field of geodesy, geophysics, seismology, volcanology, hydrology, etc. The traditional method of long-term absolute gravity monitoring is realized by the combination of absolute gravimeter and relative gravimeter. Here we report on a new type of compact gravimeter based on atom interferometry used for long-term absolute gravity measurements. The long-term absolute gravity monitoring could be carried out with only a single instrument. Over the course of a month we took long-term absolute gravity measurements in a seismic station. With an interrogation time of 120 ms and a repetition rate of 2 Hz, the sensitivity of our cold atom gravimeter reaches 300 without any vibration isolation system, and the gravity residual fluctuations are within ±60 µGal.