An assessment of recently released high-degree global geopotential models based on heterogeneous geodetic and ocean data

The development of the state-of-the-art global geopotential model (GGM) broadens its applications in ocean science, which emphasizes the importance for model assessment. We validate the recently released high-degree GGMs over the South China Sea using geodetic observations and synthetic/ocean reanalysis data. The assessment against a recently conducted high resolution (~ 3 km) airborne gravimetric survey over the Paracel Islands shows that XGM2019e_2159 has the highest accuracy (~ 3.1 mGal). However, the comparison with airborne/shipborne data hardly discriminate the qualities of other GGMs that have or truncated to same degree and order. Whereas, the validation results of GGMs against synthetic/ocean data are not identical. XGM2019e_2159/XGM2019 has the best quality, and the accuracy of associated mean dynamic topography (MDT) is 2.5 cm, and this value changes to 7.1 cm/s (6.8 cm/s) when the zonal (meridian) geostrophic currents are assessed. In contrast, the assessments of other GGMs show that they have deteriorated accuracies compared to XGM2019e_2159/XGM2019; in particular, the widely used EGM2008 has the worst performance, and the accuracies of associated MDT and zonal (meridian) currents are reduced by 3.9 cm and 4.0 cm/s (5.5 cm/s), respectively, compared to results derived from XGM2019e_2159/XGM2019. These results suggest that the choice of GGM in oceanographic research is crucial, especially in coastal zones and regions that only fill-in data were used for GGM development. Moreover, the existing synthetic/ocean data may be served as an additional data source for global/regional gravity field assessment, which is especially useful in regions that lack of control data.

Muon Tomography applied in the Lousal Mine (Portugal)

<p>Muon Tomography is an imaging technique that uses muons, a natural background radiation, as a means of observing the the earth’s subsurface. Muons are elementary particles like electrons but with a much greater mass that gives them a high penetrative power across matter. With suitable detectors it is possible to create muographs (muon radiographs) to obtain the column density distribution of the surveyed region. This project is a collaboration between University of Évora and the Laboratory of Instrumentation and Experimental Particle Physics (LIP). Both are Portuguese institutions that intend to apply the muon tomography in the geophysics field. The chosen location was the Lousal Mine, an abandoned and well mapped mine in Portugal with all the support infrastructures necessary that make it an ideal location to test the muon telescope developed by us. The detection will take place inside a mine gallery about 18 m below the surface. The telescope will do a geological reconnaissance of the ground above the gallery with the intention of mapping structures and ore masses already known and of improving the existing information with new data. This will serve to test the performance and sensitivity of the muon telescope, made of particle detectors called RPCs. A working prototype was put in place to gather preliminary information and establish the requirements of the equipment. After that, a muon telescope equipped with four RPC detectors, with an area of 1 m<sup>2</sup> each, was assembled and has been collecting muons inside the Lousal Mine for the last few months. The tomographic aspect of the work is born from placing the telescope in different locations inside the mine and by orienting it to observe in different directions. Simulations of the muons detection have been made using GEANT4 software. The simulations allow to study the expected result of muographs produced by the muon flux passing through a simulated ground with different characteristics. The aim of this work is to combine the muography information with gravimetry data, from a gravimetric survey that will be carried on site, through a joint inversion of both data sets in order to obtain 3D density profiles of the observed region. Other geophysical methods are being applied above the mine to survey the surface, using photogrammetry, and the ground, using GPR and seismic refraction. These methods give knowledge about the arrangement of the ground, can be compared with previous acquired information and will help to perfect the 3D density profiles.</p>

Development of a MEMs gravimeter for drone-based field surveys.

<p>Gravimetry allows us to study sub-surface structures remotely by measuring changes in Earth's surface gravitational field and using this data to infer the density of geological structures. Of its wide range of applications, it is mostly used in the oil and gas exploration industry, volcanology, civil engineering and even archaeological studies. Airborne gravimetry is a vital method of conducting a spatial gravimetric survey in areas which are difficult to access by foot, such as mountains. Generally, sensors are modified for air crafts platforms by installing them on large gimbal systems, or a strap-down gravimeter can be used as a lower-cost alternative. Now, a new MEMs gravimeter called “Wee-g” is enabling the development of a system to deploy the gravimeter on an unmanned aerial vehicle (UAV or drone). Wee-g was first developed with the objective of developing a low-cost MEMS accelerometer for gravimetric use which could be manufactured on a large scale. In 2016, Wee-g was used to measure Earth tides - the elastic deformation of the Earth caused by gravitational fields of the Moon and Sun. Since then, the device electronics have been miniaturised to make the system portable and has been tested at the Campsie Hills just north of Glasgow. Work is underway to build an isolation platform with active stabilisation on which the Wee-g can be mounted to be deployed on a drone which will reduce airborne surveys costs further and allow for more airborne gravimetric surveys to be carried out in remote locations.</p>

GRAVIMETRIC SURVEY POINTS POSITIONING SUPERVISING USING PPP

In article the technique of supervising of GNSS-measurements for navigational and geodedic support of ground geophysical works is considered. The technique contains Precise Point Positioning GNSS post-processing with free software and online-services.

Gravimetric survey and modeling of the basement morphology in the sedimentary thickness characterization, NE portion of Paraná Sedimentary Basin - Brazil

ABSTRACT: The northeast portion of the Paraná Sedimentary Basin is distinguished by structural highs as the known Pitanga Dome, an uplifted structure identified in the last century. It represents a geological and evolutionary evidence of the Paraná Sedimentary Basin and has undergone inspired studies and intense exploration surveys. This study consists of a gravimetric survey in the Pitanga Dome area, State of São Paulo, Brazil. The Bouguer gravity anomalies have been identified and related to the structural high, sedimentary thickness, and the basement morphology. Processing and enhancement techniques were used for forward modeling based on previous studies. The three models from profiles sectioning the dome have a sedimentary thickness varying from 200 to 1.250 meters. The adopted methodology has provided important results determining that the Pitanga Dome can be understood through rational 3D visualization. The area can be interpreted as an undulating basement with thinning of sedimentary rocks related to deep features (structures) in the crust/mantle limit (Moho uplift). This characteristic is confirmed by the sedimentary layer thickening present throughout the surrounding area. The results also offer important insights and support for further studies concerning the genesis and evolution of this and other uplifted structures of the Paraná Sedimentary Basin.