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Topographic mapping and ocean charting are the outputs of two main surveying techniques for which data has been collected independently for long time. In recent years there has been a growing aware...

The tectonic–geodynamic characteristics of the North African–Arabian region are complicated by the interaction of numerous factors. To study this interaction, we primarily used satellite gravimetric data (retracked to the Earth’s surface), which has been acknowledged as a powerful tool for tectonic–geodynamic zoning. The applied polynomial averaging of gravity data indicated the presence of a giant, deep quasi-ring structure in the Eastern Mediterranean, the center of which is located under the island of Cyprus. Simultaneously, the geometrical center of the revealed structure coincides with the Earth’s critical latitude of 35°. A quantitative analysis of the obtained gravitational anomaly made it possible to estimate the depth of the upper edge of the anomalous body as 1650‒1700 km. The GPS vector map coinciding with the gravitational trend indicates counterclockwise rotation of this structure. A review of paleomagnetic data on the projection of the discovered structure into the Earth’s surface also confirms its counterclockwise rotation. Analysis of the geoid anomalies map and seismic tomography data commonly prove the presence of this deep anomaly. The structural and geodynamic characteristics of the region and paleobiogeographic data are consistent with the proposed physical–geological model. Comprehensive analysis of petrological, mineralogical, and tectonic data suggests a relationship between the discovered deep structure and near-surface processes. The deep structure also sheds light on specific anomalous effects in the upper layer of the crust, including the high-intensity Cyprus gravitational anomaly, counterclockwise rotation of the Mesozoic terrane belt, configuration of the Sinai Plate, and asymmetry of sedimentary basins along continental faults.

The study presents an analysis of the sediment thickness compared with bathymetric and geophysical settings in the Bay of Bengal and Andaman Sea, Indian Ocean. It uses a combination of the high-resolution data: topographic GEBCO, satellite and marine gravity anomalies, EGM2008 geoid and GlobSed to visualize the correlation between relief, gravity and trends in continent-ocean sediment transport. The results include thematic maps and 3D model showing increased sediment thickness in the Bengal Fan (8,0 to 8,2 km) in NE direction with maximum in Ganges Fan (16,2 km), and southward decrease in the Andaman Sea from Irrawaddy river mouth (6-7 km) to the Strait of Malacca (1-2 km). All maps and 3D model have been plotted by Generic Mapping Tools (GMT) cartographic scripting toolset version 6.0.0.

Starting from the issue of how mean sea level has come to represent, since the early nineteenth century, the most commonly adopted vertical datum, this paper reviews the inherent biases and limitations of attempting to measure the sea from individual locations tucked away in bays and inlets along the coast. It then delves into a history of the attempts made to move measurements away from continental shores, including efforts to collect water height data from the bottom of the sea and from remote islands. Finally, it provides a history of the shift from attempting to measure the level of water at coastal locations to estimating, instead, where water ought to be. To achieve this, the article focuses on early developments in gravimetry at sea as a tool to map more precisely the geoid and, thus, the oceans’ topography. The idea behind these developments was to obtain more accurate results and a more trustworthy geodetic framework by getting rid of the variability caused by relative movement of land and sea and by contextual topographical challenges. It was also an attempt to delocalize the data collection endeavour in order to focus on inferring and estimating average values. It was thought that increasing the degree of abstraction would enable an improved representation of the planet and its oceans.

Gravity anomalies across the Indian region depict most of the geological and tectonic domains of the Indian continental lithosphere, which evolved through Archean cratonic nucleation, Proterozoic accretion, Phanerozoic India-Eurasia plate convergence, and modification through many thermal perturbations and rifting. Integrated analysis of gravity and geoid anomalies together with topographic and heat flow data led to deciphering the mechanism of isostatic compensation of topographic and geological loads, lithospheric structure, and composition. This study discusses the nature of gravity (free-air, Bouguer and Isostatic) and geoid anomalies in relation to the topography, geology, and tectonics, and presents a lithospheric density model across the peninsular India and Himalaya. Southern peninsular Indian region shows relatively low Bouguer gravity anomalies compared to the northern region. The mobile belts are generally observed to have relatively higher Bouguer gravity anomalies, e.g., Eastern Ghats Mobile Belt compared to the shield regions. The gravity lows are observed over topographic features like the Western Ghats and Himalaya, while some of the topographic highs like Aravalli show positive gravity anomaly. The Indian Ocean Geoid Low varies from -82 m over Dharwar Craton to -98 m over the Southern Granulite Terrain and finally reaches a significant low of -106 m in the Indian Ocean. Flexural isostatic compensation with variable Effective Elastic Thickness (EET) ~10 km to 50 km prevails over the stable continental region. The lithospheric thickness varies from 80 km along the coastal region to 120-130 km beneath the Saurashtra Plateau, the Southern Granulite Terrain, and the Eastern Indian Shield, and reaches to more than 200 km under the Himalayan orogenic belt in the north. From Dharwar Craton to Bundelkhand Craton in central India, the lithospheric thickness varies between 160 and 180 km.

Geophysical data from open sources are widely used as support of integrated analysis in regional geologic studies in seismically active areas, such as Mexico. High seismicity with repetitive earthquakes occurs in areas of the subduction zones formed during the tectonic evolution and correlates with geophysical anomalous fields. This paper investigates the correspondence between the geophysical, topographic and seismic setting of Mexico using Generic Mapping Tools (GMT) scripting toolset for data processing. The approach for automated mapping using GMT console and shell scripts is presented as an advanced cartographic method aimed to get insights into in the geology and geophysics of Mexico. The data were obtained from open source high-resolution datasets: GEBCO, EGM-2008, satellite-derived gravity, EMAG2 magnetic anomaly and IRIS seismic database. The correspondence between the geological and geophysical data of Mexico has been verified through the comparison between the thematic maps, regional distribution of gravity anomalies and locations of earthquakes. Seven new maps are performed on geologic, geophysical, topographic and seismic data. Seismic mapping is presented for the period of 2007-2021 demonstrating events with magnitude from 1.5 to 7.2. The impact of tectonic processes that formed Middle American Trench and active Trans-Mexican Volcanic Belt on high regional seismicity with intensive earthquakes is explored. The study finds that GMT is an effective tool for high-quality mapping and cartographic analysis. The IRIS data can be used for geologic analysis of Mexico. Dados geof��sicos de fontes abertas s��o amplamente usados como suporte de an��lise integrada em estudos geol��gicos regionais em ��reas sismicamente ativas, como o M��xico. Alta sismicidade com terremotos repetitivos ocorre em ��reas das zonas de subduc����o formadas durante a evolu����o tect��nica e se correlaciona com campos an��malos geof��sicos. Este artigo investiga a correspond��ncia entre o cen��rio geof��sico, topogr��fico e s��smico do M��xico usando o conjunto de ferramentas de script Generic Mapping Tools (GMT) para processamento de dados. A abordagem para mapeamento automatizado usando o GMT e scripts de shell �� apresentada como um m��todo cartogr��fico avan��ado com o objetivo de obter insights sobre a geologia e a geof��sica do M��xico. Os dados foram obtidos de conjuntos de dados de alta resolu����o de c��digo aberto: GEBCO, EGM-2008, gravidade derivada de sat��lite, anomalia magn��tica EMAG2 e banco de dados s��smico IRIS. A correspond��ncia entre os dados geol��gicos e geof��sicos do M��xico foi verificada atrav��s da compara����o entre os mapas tem��ticos, distribui����o regional de anomalias gravitacionais e localiza����es de terremotos. Sete novos mapas s��o realizados em dados geol��gicos, geof��sicos, topogr��ficos e s��smicos. O mapeamento s��smico �� apresentado para o per��odo de 2007-2021 demonstrando eventos com magnitude de 1,5 a 7,2. O impacto dos processos tect��nicos que formaram a trincheira da Am��rica Central e o cintur��o vulc��nico transmexicano ativo na alta sismicidade regional com terremotos intensos �� explorado. O estudo concluiu que o GMT �� uma ferramenta eficaz para mapeamento e an��lise cartogr��fica de alta qualidade. Os dados IRIS podem ser usados para an��lises geol��gicas do M��xico.

International audience; Along with the development of the scripting technology in cartography, such as the Generic Mapping Tools (GMT) and libraries of R programming language, geologic and geophysical mapping is being vigorously promoted, where the integration of the thematic data, such as GEBCO/SRTM, EGM-2008 and open geological raster and vector layers is one of the primary datasets that provides the highresolution raw sources for cartographic visualization in the geologically complex regions like Pakistan. This study aims to integrate scripting methods of automated cartography, methods of applied geoinformatics for geomorphometric analysis and technical data processing (formatting, projecting, plotting), to provide a synthesis of the geological, geophysical and geomorphological maps of Pakistan they as new information supporting analysis of the geospatial variations of geology, geomorphology, tectonics and gravity fields with a special focus on the geologically remarkable region of Pakistan: Sulaiman Fold Belt and Muslim Bagh ophiolite complex. This study presents new 12 thematic maps, which are technically made using scripting approaches and open tools. All maps cover the region of Pakistan and they are made using open source tools: GMT, R and QGIS. A GMT and R based scripting mapping is applied for mapping Pakistan, and its algorithm steps are presented stepwise as code snippets. A system complex approach of the data integration and formats reshaping, data conversion and reformatting for a single project of the geology of Pakistan is designed and developed based on the combination of the programming and scripting techniques and with additional QGIS based mapping, which effectively integrates the thematic geospatial multi-origin datasets. Various color palettes and cartographic visualization approaches have been used to achieve the best visualization. The resulting maps are explained and discussed. Correlation between spatial phenomena of Earth's gravity, geologic evolution and tectonic movements were pointed out and commented on. New 12 maps present the regional geologic setting of the country.

International audience; This paper presents the GRASS GIS-based thematic mapping of Antarctica using scripting approach and associated datasets on topography and geophysics. The state-ofthe art in cartographic development points at two important aspects. The first one comprises shell scripting promoted repeatability of the GIS technique, increased automatization in cartographic workflow, and compatibility of GRASS with Python, PROJ and GDAL libraries which enables advanced geospatial data processing: converting formats, re-projecting and spatial analysis. The second aspect is that data visualization greatly influences geologic research through improving the interpretation between the Antarctic glaciation and surface. This includes the machine learning algorithms of image classification enabling to distinguish between glacier and non-glacier surfaces through automatically partitioning data and analysis of various types of surfaces. Presented detailed maps of Antarctic include visualized datasets from the ETOPO1, GlobSed, EGM96 and Bedmap2 projects. The grids include bed and surface elevation, ETOPO1-based bathymetry and topography, bed, ice and sediment thickness, grounded bed uncertainty, subglacial bed elevation, geoid undulations, ice mask grounded and shelves. Data show the distribution of the present-day glacier, geophysical fields and topographic landforms for analysis of processes and correlations between the geophysical and geological phenomena. Advances in scripting cartography are significant contributions to the geological and glaciological research. Processing high-resolution datasets of Southern Ocean retrieved by remote sensing methods present new steps in automatization of the digital mapping, as presented in this research, and promotes comprehensive monitoring of geological, permafrost and glacial processes in Antarctica. All maps have been plotted using GRASS GIS version 7.8. with technical details of scripts described and interpreted.

We present a three-dimensional (3D) density model of northern Andaman subduction zone (10°–15°N) constructed through joint modelling of satellite free-air gravity and geoid anomalies with constraints from previous studies. This novel modelling approach utilizes geoid and gravity anomalies simultaneously to better resolve the structure of inadequately known part of the subduction zone. The density model suggests: • A contrasting situation of subducting Indian plate, mapped up to a depth of ∼180 km in the southern part, and almost missing in the north of the study region. • Dip of the Benioff zone and the width of the accretionary prism decreases from south to north. • Nature of the overriding plate varies from oceanic to semi-continental towards the north. • Moho depth is relatively higher under the seamounts and 90°E ridge. The change in the subduction geometry is probably due to the subducting aseismic ridge, difference in the sediment influx and variation in the convergence rates. The absence of the subducting slab in the north is probably caused due to tearing between northern Andaman in the south and Burmese Arc in the north.

We present the official land uplift model NKG2016LU of the Nordic Commission of Geodesy (NKG) for northern Europe. The model was released in 2016 and covers an area from 49° to 75° latitude and 0° to 50° longitude. It shows a maximum absolute uplift of 10.3 mm/a near the city of Umea in northern Sweden and a zero-line that follows the shores of Germany and Poland. The model replaces the NKG2005LU model from 2005. Since then, we have collected more data in the core areas of NKG2005LU, specifically in Norway, Sweden, Denmark and Finland, and included observations from the Baltic countries as well. Additionally, we have derived an underlying geophysical glacial isostatic adjustment (GIA) model within NKG as an integrated part of the NKG2016LU project. A major challenge is to estimate a realistic uncertainty grid for the model. We show how the errors in the observations and the underlying GIA model propagate through the calculations to the final uplift model. We find a standard error better than 0.25 mm/a for most of the area covered by precise levelling or uplift rates from Continuously Operating Reference Stations and up to 0.7 mm/a outside this area. As a check, we show that two different methods give approximately the same uncertainty estimates. We also estimate changes in the geoid and derive an alternative uplift model referring to this rising geoid. Using this latter model, the maximum uplift in Umea reduces from 10.3 to 9.6 mm/a and with a similar reduction ratio elsewhere. When we compare this new NKG2016LU with the former NKG2005LU, we find the largest differences where the GIA model has the strongest influence, i.e. outside the area of geodetic observation. Here, the new model gives from − 3 to 4 mm/a larger values. Within the observation area, similar differences reach − 1.5 mm/a at the northernmost part of Norway and − 1.0 mm/a at the north-western coast of Denmark, but generally within the range of − 0.5 to 0.5 mm/a.

In this study, the Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) gravitational gradients in the North China Craton (NCC) are processed. The normal gravitational gradient correction, the downward continuation from the mean orbit altitude to the geoid, and the gravitational gradient corrections for the topography, sediment, Moho undulations and the deep-source field are taken into account. After processing, the residual gravitational gradient anomalies corresponding to density heterogeneities are acquired. The preconditioned conjugate gradient method is introduced to invert the density structures using the roughness matrix to constrain the density distribution and the depth-weighting function to prevent the density distribution from migrating to the top of the model due to the decay of the gravitational gradient kernel with depth. The density structure derived from the seismic tomography is used as the initial model, and the GOCE gravitational gradient anomalies are used to invert the density structures in the NCC using the preconditioned conjugate gradient method. The results show that the density structures of the NCC lithosphere reflect obvious lateral and vertical heterogeneities. The density structure in the eastern part of the NCC is different from that in the western part of the NCC. The distribution of the density anomalies corresponds to the tectonic characteristics. The density structures in Taihang Mountain exhibit segmentation features. The thinning of the lithosphere observed in the NCC may extend into the northern part of Taihang Mountain. The density changes significantly within the area between the Ordos Block and the Qilian Block, which corresponds with the different lithospheric features in these two blocks.

The airborne Operation IceBridge and spaceborne CryoSat-2 missions observe polar sea ice at different spatial and temporal scales as well as with different sensor suites. Comparison of data products from IceBridge and CryoSat-2 is complicated by the fact that they use different geophysical corrections: reference ellipsoid, geoid model, tide model, and atmospheric corrections to derive surface elevation and sea-ice freeboard. In this paper, we compare sea-ice surface elevation and freeboard using eight coincident CryoSat-2, Airborne Topographic Mapper (ATM), and Land, Vegetation, and Ice Sensor (LVIS) observations with direct IceBridge underflights of CryoSat-2 ground tracks. We apply identical geophysical corrections to CryoSat-2 and IceBridge data to eliminate elevation biases due to these differences and focus on differences due to retracker performance. The IceBridge ATM and LVIS elevation and freeboard and Snow Radar snow depth data sets are averaged to each CryoSat-2 footprint for comparison. With snow depth measurements, we are able to compare elevations and freeboards at the snow/ice interface for five different CryoSat-2 retrackers (ESA, GSFCv1, AWI, JPL, and GSFCv2) and IceBridge. The overall mean of freeboard differences between GSFCv2, ESA, AWI, JPL retrackers, and ATM are in agreement within 0.05 m. However, the five different CryoSat-2 retrackers show distinct differences in mean elevation over leads and over floes. This suggests that the physical interpretation of the different retrackers needs to be considered depending on usage, for example, elevations from CryoSat-2 retrackers need to be carefully calibrated before comparing with elevation from other satellites for long-term surface elevation trends.

We present a new approach to estimate time variations in J2. Those variations are represented as the sum of contributions from individual sources. This approach uses solely Gravity Recovery And Climate Experiment (GRACE) data and the geoid fingerprints of mass redistributions that take place both at the surface and in the interior of the solid Earth. The results agree remarkably well with those based on satellite laser ranging, while estimates of the sources explain the observed variations in J2. Seasonal variations are dominated by terrestrial water storage and by mass redistribution in the atmosphere and ocean. Trends, however, are primarily controlled by the Greenland and Antarctic ice sheets and by glacial isostatic adjustment. The positive trend from surface mass variations is larger than the negative trend due to glacial isostatic adjustment and leads to an overall rising trend during the GRACE period (2002–2017).

Due to uncertainty of single-method interpretation we applied 2-D integrated lithospheric modelling along three CELEBRATION 2000 profiles CEL01, CEL04 and CEL05. Modelling of the lithospheric thermal structure is based on the joint interpretation of gravity, geoid, topography and surface heat flow data with temperature-dependent density. The models for each profile were constrained by seismic modelling results of the large-scale international project CELEBRATION 2000. The results indicate large variations of the lithosphere thickness from the old and cold East European Craton (~200 km) and the Trans European suture zone via the Western Carpathian orogeny to the young and hot Pannonian Basin (~90 km). Important differences in the lithospheric thickness were also found along-strike of the Western Carpathian orogeny and the Trans-European Suture Zone. The western part of the Western Carpathians is characterized by weak thickening of the lithosphere (only about 145 km), while their eastern segment presents strong lithospheric thickening (~190 km). The Malopolska unit in southern Poland has a lithospheric thickness of about 130 km. Thickest lithosphere (220 km) is observed around the junction of the Carpathian Foredeep and the East-European Craton. The crustal thickness follows generally the course of the lithosphere-asthenosphere boundary. The results suggest different geodynamic evolution of the collision of the ALCAPA microplate with the European platform on the one hand and the East-European Craton on the other hand. It is suggested that the tectonic evolution of this very complex area consisting of different tectonic units has changed in time and space.

Special issue Physical properties and observations of the lithosphere-asthenosphere system.-- 21 pages, 15 figures, 3 tables, 1 appendix, The topography of the Iberian Peninsula is characterized by the presence of Variscan and Alpine orogenic belts and foreland basins, but what sets it apart from the rest of Western Europe are the large elevated flat surfaces (700 m above sea-level on average) in its central parts. The origin and support of such high average topography, whether isostatic or dynamic in nature, is a matter of intense debate. To understand Iberian topography, it is key to have a reliable image of the present-day lithospheric thermochemical structure. So far, this structure remains poorly constrained, particularly at mantle level. The goal of this paper is to derive robust estimates of the thermal, compositional and density structure of the lithosphere beneath the Iberian Peninsula from an integrated geophysical-petrological probabilistic inversion of surface wave, elevation, geoid anomaly and heat flow data. Our inversion reveals an average lithospheric thickness of 80–100 km in the Iberian Peninsula with only moderate lateral variations. The most prominent lithospheric thickness change is a steep decrease from the central to the easternmost Pyrenees. The thinnest lithosphere in our models is found below the south-eastern Mediterranean margin (, This project has been funded by Spanish Ministry of Science projects CGL2012-37222 (J. Fullea) and PGC2018-095154-B-I00 (A.M Negredo). J. Fullea is supported by an Atracción Talento senior fellowship (2018-T1/AMB/11493) funded by Comunidad Autonoma de Madrid (Spain). I. Palomeras is funded by the Beatriz Galindo fellowship (BEAGAL18/00090) co-founded by the Spanish Ministry of Education and University of Salamanca (Spain). ICM-CSIC is a Centre of Excellence Severo Ochoa (Spanish Ministry of Science and Innovation, Project CEX2019-000928-S

Este trabajo presenta un estudio detallado para la determinación del nivel medio del mar (NMM), las constituyentes de marea y un geoide de precisión en las islas Decepción y Livingston y el entorno del mar de Bransfield. Para realizar estos trabajos es necesario definir el marco de referencia geodésico, para ello se han utilizaron las redes geodésicas REGID (Red Geodésica de Isla Decepción), RENID (Red de Nivelación de Isla Decepción) y REGRID (Red Gravimétrica de Isla Decepción), utilizando como vértices fundamentales algunos puntos pertenecientes a la red RGAE (Red Geodésica Antártica Española). Los datos de marea fueron obtenidos mediante sensores de presión instalados en las estaciones mareográficas de LIVMAR y DECMAR, islas Livingston y Decepción respectivamente. Se obtuvieron las primeras series temporales con 798 días de observación en ambas estaciones, cuyo análisis armónico nos proporcionó 70 constituyentes de marea, siendo 19 las más representativas con amplitudes superiores a 1 cm. Se determinamos el nivel medio del mar, utilizando como puntos fundamentales el LN00 (I. Decepción) y BEJC (I. Livingston). Por último, se determinó el modelo de geoide de precisión, GeoiDEC14, calculado a partir de mediciones GPS, gravimétricas y de nivelación y cuyo resultado ha sido contrastado con los modelos globales más actuales. Estos son los primeros resultados de determinación del nivel medio del mar y la obtención de un modelo de geoide de precisión en esta zona de la Antártida y mejoran trabajos previos realizados en la región.

Based on our update to the global map of the proposed paleoshorelines from the 1980s using high-quality global image and topography data acquired since the late 1990s, this chapter assesses how they were most likely formed (wave action, wind-driven push or thermal expansion of an ice cover, or low-viscosity volcanic plains emplacement). Shorelines follow an equipotential surface with respect to the planetary geoid. On Earth, abandoned shorelines deviate from equipotential surfaces because the water load depresses the crust and mantle by up to one-third the water depth. When the water is removed, the crust rebounds such that shorelines around islands can often be elevated with respect to those along the basin margin. By determining shoreline elevations, we looked for evidence of rebound or subsidence, with implications for the fate of the water and the rheology of the crust.

The existing coordinate system for the entire country of Ecuador is the Provisional South American Datum of 1956 (PSAD56) which originated in La Canoa, Venezuela. This coordinate system is considered one of the major datums of the world and is generally associated with the countries of South America that comprise the Andes Mountain Range. The system is referenced to the International Ellipsoid and is rigorously constrained by gravimetric observations. Shortly after the fall of the Iron Curtain, the traditionally classified gravity system of the U.S. Department of Defense was offered to private geodesists on a case-by-case basis. The Guayaquil project was one of those offered access to the WGS84 geoid. The availability of cartographic data in different datums made it necessary to create a new application software. This software needs to look at the input and output of all the components and consolidate all the information into a final depository a block based Geographical Information System (adjusted to the World Geodetic System 1984 using Normal Mercator projection). This paper shows a Molodensky seven parameter transformation shift from a PSAD56 classical geodetic system to WGS84 Word Geodetic System 1984 for precise urban mapping applications. All future work within the city of Guayaquil will be able to use the GPS technology with no systematic bias. Such facility using the PSAD56 system is not possible.

This article analyzes topographical and geological settings in the Japan Archipelago for comparative raster data processing using GRASS GIS. Data include bathymetric and geological grids in NetCDF format: GEBCO, EMAG2, GlobSed, marine free‐air gravity anomaly and EGM96. Data were imported to GRASS by gdalwarp utility of GDAL and projected via PROJ library. Method‐ ology includes data processing (projecting and import), mapping and spatial analysis. Visualization was done by shell scripting using a sequence of GRASS modules: ‘d.shade’ for relief mapping, ‘r.slope.aspect’; for modelling based on DEM, ‘r.contour’ for plotting isolines, ‘r.mapcalc’ for classification, ‘r.category’ for associating labels, and auxiliary modules (d.vect, d.rast, d.grid, d.legend). The results of the geophysical visualization show that marine free‐air gravitational anomalies vary in the Sea of Japan (–30 to above 40 mGal) reflecting density inhomogeneities of the tectonic structure, and correlating with the geo‐ logical structure of the seafloor. Dominating values of geoid model are 30–45 m reflecting West Pacific rise, determined by deep density inhomogeneities associated with the mantle convention. Sediment thickness varies across the sea reflecting its geological development with density of 2 km in its deepest part and thinner in central part (Yamato Rise). The aspect map and reclassified map express gradient of the steepest descent.

The effects of temporal changes in the marine geoid on estimates of the ocean dynamic topography are being investigated. Influences from mass redistribution due to changes of land hydrology, ice sheets, glacial isostatic adjustment (GIA), and ocean and atmospheric dynamics are considered, and the associated crustal deformation is included. The strongest signals are associated with the seasonal cycle caused by changes in terrestrial water storage and ice sheets as well as the redistribution of atmospheric mass. Second to this is the importance of an overall trend caused by GIA and decreasing ice sheets over Greenland and Antarctica. On long spatial scales, the amplitude of regional trends estimated for the geoid height has a sizable fraction of those from sea level anomaly (SLA) for the period 1993–2016, also after subtraction of steric height of the upper 1,000 m to analyze trends in deep ocean geostrophic currents. The estimated strong negative geoid height trend south of Greenland for the period 1993–2016 opposes changes in dynamic sea level for the same period thereby affecting past studies on changes of both the strength of the subpolar gyre based on SLA and the meridional overturning circulation on a section between Cape Farewell and Portugal applying ocean dynamic topography and hydrography. We conclude that temporal geoid height trends should be considered in studies of (multi)decadal trends in sea level and circulation on large spatial scales based on altimetry data referenced to a geoid field., Plain Language Summary: Changes in ocean surface currents are routinely obtained from satellite altimetry data. A correction for changes in the geoid, the equipotential surface of gravity closest to sea level, is considered small and thus usually neglected. We investigate temporal geoid height changes and potential implications on ocean circulation studies using space‐borne gravity data and results from ocean and atmosphere models to discover the individual processes of mass redistribution in the climate system causing thereby changes in the geoid height. We found the largest signals in the seasonal cycle for terrestrial hydrology in the Amazone basin and in negative trends for the Greenland and West Antarctic Ice sheets. For the period 1993–2016 and on spatial scale larger than 1,000 km or so the magnitude of the negative marine geoid height trend south of Greenland is similar to the strength of the negative trend in geocentric sea level from altimetry. This outcome affects past studies on changes in the strength of the subpolar gyre and the Atlantic meridional overturning circulation that neglect geoid height variations. We conclude that temporal geoid height trends should be considered in studies of (multi)decadal trends in sea level and circulation on large spatial scales based on altimetry data., Key Points: The strongest geoid height changes are associated with regionally pronounced seasonal signals and secular trends. In the Subpolar North Atlantic the geoid height trend biases circulation trend estimates based on altimetry. Altimetry data need correction for geoid height change when long‐term variations in ocean dynamics are studied., German Science Foundation (DFG), BMBF funded Verbundprojekt RACE (Regional Atlantic Circulation and Global Change), DFG http://dx.doi.org/10.13039/100004807

The study investigated geomorphology of the Japan Trench located east of Japan, Pacific Ocean. A high-resolution GEBCO Gridded Bathymetric Dataset was used for modeling, mapping and visualization. The study aimed to compare and analyse variations in the geomorphic structures of the two parts of the trench and to visualize variations in the geological, geophysical and bathymetric settings. Technically, the cartographic work was performed using scripting based on the Generic Mapping Toolset (GMT). Modelled cross-sectioning orthogonal profiles transecting the trench in a perpendicular direction were automatically digitized and graphed in the two segments. The results of the bathymetric analysis shown that the southern part is shallower: with deeper values in absolute (139 samples between –7000 to –8000 m) and statistical records (the most frequent values are within –5500 to –5800 m) comparing to the northern segment (–5300 to –5500 m). The geomorphological analysis shows a more complicated relief in the northern part of the trench, which has a higher seismic activity. The southern part has a gentler slope on the Honshu island side. The geoid modeling along the trench ranges in 0–20 mGal. The highest values are recorded by the Honshu Island (>40 mGal). The rest of the area has rather moderate undulations (20–40 mGal). The free-air marine gravity of the Sea of Japan is

Investigation of deep crustal and lithospheric structures is essential to understand the nature of geodynamical processes beneath the Himalaya and Tibetan plateau of the India-Eurasia collision zone. Our density cross sections across the Himalaya-Eurasia collision zone using integrated 2-D modeling of gravity, topography, and geoid data incorporating constraints from seismic information supports the above contention. Analysis of gravity, geoid, and elevation data over the interior of the Tibetan plateau predicts complete isostatic compensation, whereas margins of the plateau, having large topographic gradients, show lack of isostatic compensation as the Airy Moho differs from flexural Moho and seismic Moho beneath the Himalaya. Our 2-D modeled lithospheric cross sections show thick crust (~75 km) and thick lithosphere (~240 km) beneath the Himalayas and southern Tibetan plateau and relatively thin crust (~60 km) and thin lithosphere (~140 km) beneath the northern Tibetan plateau. Therefore, depth of lithosphere-asthenosphere boundary (LAB) mimics the Moho relief. Thinner crust and thin lithosphere under northern Tibetan plateau suggest the importance of the mantle isostasy where the temperature is anomalously high. This corroborates with the presence of recent potassic volcanism, inefficient Sn propagation, east and southeast oriented global positioning system displacements, and large shear wave splitting anisotropy (>2 s). Excellent correlation between effective elastic thickness and lithospheric thickness predicts hot and deformable lithosphere in the northern Tibet and underthrusting of cold Indian mantle beneath the Himalayas.

Almost half of the Earth&rsquo, s land is covered by large river basins. Temporal variations of hydrological masses induce time-varying gravitational potential and temporal mass loading that deforms the Earth&rsquo, s surface. These phenomena cause temporal variations of geoid/quasigeoid and ellipsoidal heights that result in temporal variations of orthometric/normal heights &Delta, H/&Delta, H*. The aim of this research is to assess &Delta, H* induced by hydrological masses over large river basins using the Gravity Recovery and Climate Experiment (GRACE) satellite mission data. The results obtained reveal that for the river basin of a strong hydrological signal, &Delta, H* reach 8 cm. These &Delta, H* would be needed to reliably determine accurate orthometric/normal heights. The &Delta, H* do not exceed &plusmn, 1 cm in the case of the river basin of the weak hydrological signal. The relation between hydrological mass changes and &Delta, H* was investigated. Correlations between &Delta, H* and temporal variations of equivalent water thickness were observed in 87% of river basins subareas out of which 45% exhibit strong correlations. The &Delta, H* determined over two river basins that characterize with the strongest and weakest temporal variations were analysed using the Principal Component Analysis method. The results obtained reveal that &Delta, H* in subareas of the same river basin can significantly differ (e.g., &plusmn, 2 cm in the Amazon basin) from each other, and are strongly associated with different spatio-temporal patterns of the entire river basin.

Author(s): Kachuck, SB; Martin, DF; Bassis, JN; Price, SF | Abstract: The ice sheets of the Amundsen Sea Embayment (ASE) are vulnerable to the marine ice sheet instability (MISI), which could cause irreversible collapse and raise sea levels by over a meter. The uncertain timing and scale of this collapse depend on the complex interaction between ice, ocean, and bedrock dynamics. The mantle beneath the ASE is likely less viscous (∼1018 Pa s) than the Earth's average mantle (∼1021 Pa s). Here we show that an effective equilibrium between Pine Island Glacier's retreat and the response of a weak viscoelastic mantle can reduce ice mass lost by almost 30% over 150 years. Other components of solid Earth response—purely elastic deformations and geoid perturbations—provide less stability than the viscoelastic response alone. Uncertainties in mantle rheology, topography, and basal melt affect how much stability we expect, if any. Our study indicates the importance of considering viscoelastic uplift during the rapid retreat associated with MISI.

The study is geographically focused on the Manila Trench, located in the west Pacific Ocean, South China Sea, west Philippines. The research aims at the geological mapping, analysis and visualizing variations in the submarine geomorphology of the Manila Trench. Technically, the work was done using Generic Mapping Tools scripting toolset (GMT). A combination of various GMT modules was applied for geospatial modelling. Methodology includes cartographic data integration and interpretation through approaches of data analysis: topographic plotting, geophysical modelling, geological mapping and statistical analysis. The data included SRTM, ETOPO1, geoid and gravity grids (CryoSat-2, Jason-1). Two sets of the cross-section profiles of the trench were automatically digitized. The profile transects were compared and differences in the geomorphic shape in southern and northern parts revealed. Southern part has steeper slope on the western part. Northern part is steeper on the continental slope part. The submarine terraces are located on the northern segment at depths -2,000 m. The depth and geomorphology of the slope vary for the range -3,500 to -4,500 m: minimals for the northern part with 526 samples (18.2%) for the depths -4,000 to -4,200 m. The histogram for the northern part has bimodal distribution with two peaks. The southern part shows 142 values for the minimals -3,500 to -3400 m. The statistical analyses revealed that northern part of the trench is deeper. The GMT functionality shown in this paper enabled integration and interpretation of the multi-source data: automatically digitized profiles, geological mapping, 2D and 3D bathymetric modelling, statistical analysis, mathematical approximation of the trend modelling. The GMT proved to be capable of visualizing geodata that can significantly improve Earth studies and interpretation of submarine geomorphology of the oceanic trenches through the advanced data analysis.

International audience; The papers presents an integrated processing of the high-resolution thematic data covering the area of the Beaufort Sea, a marginal sea of the Arctic Ocean, northern Canada and Alaska. Five thematic maps of the Beaufort Sea, Arctic Ocean are presented. The cartographic techniques were performed by Generic Mapping Tools (GMT) scripting toolset. The methodology presents the integration of the multi-source high-resolution thematic datasets: bathymetric GEBCO, IBCAO, topographic GLOBE, sediment thickness GlobSed, EGM2008 geoid model, GMT vector layers and geophysical gravity model from CryoSat-2 and Jason-1. There is an agreement with the data by their inspection and analysis of grids correlation. The bathymetric map demonstrated variations in depths with rapidly decreasing values in the Mackenzie River coasts, depicting the basin of the Beaufort Sea, large shelf in the Canadian Arctic Archipelago and western part bordering the Chukchi Sea. The GDAL inspection shows that the GEBCO-based topography ranges between -3,973 m to 2,578 m. Gravity data shows that coastal areas in northern Canada and Alaska have values >20 mGal while the basin of the Beaufort Sea is dominated by the lower values at -65 to -45 mGal; the data range is from -155.097 to 366.939 mGal. The marine free-air gravity fields and geoid data demonstrate correlation with topographic isolines of the region. The data range for the sediment thickness is from 0.00 to 18064.53 m having maximal data at the Mackenzie River discharge area. A comprehensive compilation of the data on the Beaufort Sea visualized using GMT presents more insights into its bathymetric structure and geophysical fields distribution in context of the variability of the geological settings.

In geodesy three surfaces, the physical surface of the earth, the geoid and the reference ellipsoid are encountered giving rise to orthometric height (h), the ellipsoidal height (H) and the geoidal separation (N). The orthometric height and the ellipsoidal height are with reference to the geoid and the reference ellipsoid respectively. The vertical separation between the ellipsoid and the geoid is the geoidal separation. A mathematical relation depicting the surface of the geoid with regard to the reference ellipsoid is the geoid model. It relates the geoidal separation with the horizontal location.The Global Navigational Satellite System provides precise location of points on the surface of the earth. The vertical location provided is the ellipsoidal height which needs conversion to a more usable format, the orthometric height. This is done by integrating ellipsoidal heights with a geoid model. The accuracy of conversion depends on the accuracy of geoid model. Therefore, development of geoid model has become a current area of research in geodesy.Objective of this study is to develop a local geoid model by employing various polynomial models and thereafter to analyse the accuracy of these models. The test area is in Papua New Guinea. The geometric method is used for computation of the geoidal separation from ellipsoidal and orthometric heights and thereafter the horizontal coordinates and the geoidal separation are used to develop the geoid surface using second, third and fourth degree polynomials. The study shows that the third degree polynomial provided an accuracy of ±20 cm. Keywords: Geodesy, Orthometric height, Ellipsoidal height, Geoidal separation, Geoid model

The application of satellite altimetry over inland waters requires a proper modelling of the various error sources involved in the determination of precise surface water heights above a reference ellipsoid or above the geoid. The objectives of this study are firstly the analysis of the errors present on the dry tropospheric correction (DTC) and on the wet tropospheric correction (WTC) provided in the CryoSat-2 (CS-2) products and secondly the development of methodologies to derive improved corrections, aiming at getting improved products for CS-2. This study is conducted on selected regions of interest, such as the Amazon and Danube rivers, Titicaca and Vanern lakes and the Caspian Sea. Since CS-2 has a geodetic orbit, its ground tracks allow the retrieval of precise surface water heights over regions not covered by any other satellite. The DTC and WTC present in the CS-2 products have been compared against corrections computed from the European Centre for Medium-Range Weather Forecasts (ECMWF) operational model at various levels: (i) the level of ECMWF model orography; (ii) the level of the Altimetry Corrected Elevations 2 (ACE2) digital elevation model and (iii) the level of mean lake/sea or river profile. An independent assessment of the corrections has also been performed by comparison with DTC derived from in situ surface pressure measurements and WTC retrieved from Global Navigation Satellite Systems (GNSS) data. Results show that the model-derived corrections present on CS-2 products seem to be referred to the model orography, except for the Caspian Sea where corrections seem to be referred to mean sea level (zero level). Model orography can depart from the mean river profile or mean lake/sea heights by hundreds of meters. Overall, ACE2 DEM is a better altimetric surface than ECMWF orography, however height errors up to hundreds of meters exist in ACE2. Height errors induce DTC errors that can reach several centimetres (11 cm in the Danube River) and WTC errors up to 2–3 cm. These errors are systematic, having always the same sign and magnitude for a given location, thus affecting the retrieval of the absolute water level. For rivers, the mean profile is the best representation of the surface height in the river basin and is also the best reference surface for use in the DTC and WTC estimations from an atmospheric model. The same happens with lakes or closed seas, where the corrections should be referred to the mean lake/sea level. Results show that, once computed at the correct mean river profile or mean lake/sea level, the DTC has a small variation, with a standard deviation going from 0.5 cm in the Amazon River to 3.0 cm in the Danube River. The DTC absolute values go from 1.48 m in Lake Titicaca to 2.32 m in the Caspian Sea. With a larger variability, once computed at mean river profile or mean lake/sea level, the standard deviation of the WTC goes from 2.7 cm in Lake Titicaca to 5–6 cm in all other regions and absolute values from only 6 cm in Lake Titicaca to 31 cm in the Amazon River. Once computed at the correct surface elevation the corresponding errors are expected to be less than 1 cm for the DTC and less than 2 cm for the WTC.

Deriving a quantitative geodynamical interpretation from tomography models is a difficult task. It is also a timely task, particularly given the many high-resolution tomography models published in recent years. It is important to assess mantle structure in terms of density and temperature anomalies. Here, we provide a new estimation of the conversion factors between seismic velocity anomalies and density anomalies, Rρ/v, and between seismic velocity anomalies and temperature anomalies, RT/v. These conversion factors are found by considering the constraints provided by thermodynamics, the influence of melt, and anelasticity. To determine the elastic component, we performed thermodynamic simulations by considering several compositions representative of normal or plume-enriched mantle. We also explore the effects of the presence of melt on seismic velocity and consider a radial attenuation profile to account for anelasticity. We provide an envelope of acceptable models, by combining the range of possible solutions combining the elastic, anelastic, and melt relationships used in deriving the conversion factors. Several of the frequently used velocity-density scaling relationships are encompassed in this envelope. We assess the validity of our result by calculating temperature anomalies from the tomographic models using our scaling relationships—these anomalies lie within the range constrained by melting temperatures registered in volcanic rocks (±300 K). Further, we show that the geoid model computed through our velocity-density scaling from the S40RTS tomography provides a good fit to the observed geoid.

The Earth masses reside in a near-hydrostatic equilibrium, while the deviations are, for example, manifested in the geoid, which is nowadays well determined by satellite gravimetry. Recent progress in estimating the density distribution of the Earth allows us to examine individual Earth layers and to directly see how the sum approaches the observed anomalous gravitational field. This study evaluates contributions from the crust and the upper mantle taken from the LITHO1.0 model and quantifies the gravitational spectra of the density structure to the depth of 435 km. This is done without isostatic adjustments to see what can be revealed with models like LITHO1.0 alone. At the resolution of 290 km (spherical harmonic degree 70), the crustal contribution starts to dominate over the upper mantle and at about 150 km (degree 130) the upper mantle contribution is nearly negligible. At the spatial resolution $$

In geodesy, orthometric and normal heights are considered as basic height systems on the earth. The reference surfaces for these heights are the geoid and quasigeoid respectively. Taking advantage of GNSS measurements, one can achieve a precise solution for the geoid and for the quasigeoid. Two methods, called direct and indirect, are worked out in this research for the computation of separation between geoid and quasigeoid in a mountainous region in the USA. The area selected for this purpose is mountainous and rough enough in order to be able to show the effect of roughness of topography in the sought quantity. The results of the two methods and testing them against GNSS-Levelling on 445 known points indicates an accuracy of 1.3 cm in RMS scale with the direct method, where there is 7 cm as an average difference between the observed geoid and quasigeoid separation and the same quantity derived from the direct method. Using Chi-squared goodness of fit test showed that the distribution of the residual quantities are normally distributed in the test area.

Global gravity models are being developed according to new data sets available from satellite gravity missions and terrestrial/marine gravity data which are provided by different countries. Some countries do not provide all their available data and the global gravity models have many vague computational methods. Therefore, the models need to be evaluated locally before using. It is generally understood that the accuracy of global gravity models is enough for local (civil, mining, construction, etc.) projects, however, our results in Iran show that the differences between synthesized values and observation data reach up to ∼300 mGal for gravity anomalies and ∼2 m for geoid heights. Even by applying the residual topographical correction to synthetized gravity anomalies, the differences are still notable. The accuracy of global gravity models for predicting marine gravity anomalies is also investigated in Persian Gulf and the results show differences of ∼140 mGal in coastal areas. The results of evaluating selected global gravity models in Iran indicate that the EIGEN-6C4 achieves the lowest RMS for estimating the geoid heights. EGM08 predicts the closest results to terrestrial gravity anomalies. DIR-R5 GOCE satellite-only model estimates the low-frequency part of gravity field more accurately. The best prediction of marine gravity anomalies is also achieved by EGM08.

This study attempts to develop a methodology to construct a high-precision geoid model (HKGEOID-2016) over Hong Kong. To achieve this objective, a hybrid method is employed in this article. The pro...

This paper describes the development of a new geoid-based vertical datum from airborne gravity data, by the Department of Survey and Mapping Malaysia, on land and in the South China Sea out of the coast of East Malaysia region, covering an area of about 610,000 square kilometres. More than 107,000 km flight line of airborne gravity data over land and marine areas of East Malaysia has been combined to provide a seamless land-to-sea gravity field coverage; with an estimated accuracy of better than 2.0 mGal. The iMAR-IMU processed gravity anomaly data has been used during a 2014-2016 airborne survey to extend a composite gravity solution across a number of minor gaps on selected lines, using a draping technique. The geoid computations were all done with the GRAVSOFT suite of programs from DTU-Space. EGM2008 augmented with GOCE spherical harmonic model has been used to spherical harmonic degree N = 720. The gravimetric geoid first was tied at one tide-gauge (in Kota Kinabalu, KK2019) to produce a fitted geoid, my_geoid2017_fit_kk. The fitted geoid was offset from the gravimetric geoid by +0.852 m, based on the comparison at the tide-gauge benchmark KK2019. Consequently, orthometric height at the six other tide gauge stations was computed from HGPS Lev = hGPS - Nmy_geoid2017_.t_kk. Comparison of the conventional (HLev) and GPS-levelling heights (HGPS Lev) at the six tide gauge locations indicate RMS height difference of 2.6 cm. The final gravimetric geoidwas fitted to the seven tide gauge stations and is known as my_geoid2017_fit_east. The accuracy of the gravimetric geoid is estimated to be better than 5 cm across most of East Malaysia land and marine areas

Different types of gravity observations are available over coastal areas. The main challenge for coastal geoid determination is the proper fusion of heterogeneous gravity data including land, shipborne, airborne, and altimetry-derived gravity data. This paper describes the gravity data fusion and the computation of the gravimetric quasigeoid in the coastal area of mainland China. An iterative procedure of the weighted least-squares prediction based on rectangular harmonic functions is used for merging the land, altimetric, shipborne, and airborne gravity data. Applying the analytical continuation method in Molodensky's theoretic frame, the merged gravity data are then used to determine the gravimetric quasigeoid model by using the generalized Stokes' integral in a remove-compute-restore fashion. The gravimetric quasigeoid model is compared with the height anomalies determined at 662 GPS leveling points over the coastal region of mainland China, where both the geodetic height and the normal height ...

En épocas recientes, las agencias federales encargadas de administrar información geográfica básica, han recibido por parte de la comunidad científica una clara reco- mendación de cambio sobre la forma de determinar el control de coordenadas verti- cales, migrando de la referencia local de nivel medio del mar hacia una referencia definida en términos de potencial del campo de gravedad como es el geoide. La principal ventaja de este cambio radica en la habilidad de hacer compatible el dátum vertical entre países de cualquier parte del mundo y compatible con la tecnología de levantamientos GNSS. En preparación para sustituir eventualmente al sistema clási- co, basado en observaciones al nivel del mar local, una gran cantidad de agencias enfrentan el reto de implementar el concepto mencionado, con datos y metodología nuevos. En este trabajo presentamos los primeros resultados de un esfuerzo de co- laboración internacional surgido desde ocho países en la región de México, Cen- troamérica y el Caribe para incrementar la capacidad técnica en esta materia y disminuir la brecha existente entre el avance científico y la implementación práctica de infraestructura de datos geodésicos para uso oficial. El geoide gravimétrico para México, Centroamérica y el Caribe GGM-CA-2015 se presenta como un modelo digital inédito en cobertura y resolución. Representa una superficie equipotencial del campo de gravedad, parametrizado por la constante W0=62636856.0m2/s2. Esta realización permite referir las coordenadas verticales para geolocalización de una gran cantidad de países e islas sobre un dátum consis- tente a través de fronteras y mares.

The Auca Mahuida volcanic field lies on the southernmost Payenia Volcanic Province, one of the broadest retroarc volcanic plateaux in the southern Central Andes (~38°S). This voluminous basaltic flooding of Quaternary age was originated from a deep asthenospheric source, interpreted as a mantle plume product of changing slab dynamics. The geometry of this source is deduced from magnetotelluric data, but the limited spatial coverage of this array does not allow a detailed resolution of this anomaly. In order to present a detailed geometry of the conductive anomaly and related crustal magmatic bodies, we used multiple data sources. We combined Magnetic and Bouguer anomalies, Curie isotherm depth (T c ), Elastic Thickness (T e ) and Moho depth derived from the Global Earth Magnetic Anomaly Grid (EMAG2) and terrestrial gravity measurements, all together in a holistic geophysical analysis. The magnetic data depict a nearly 200-km-in-diameter circular anomaly that would correspond to a dense body according to the Bouguer anomaly. Geoid data from the Gravity Field Model (EIGEN-6c4) have been filtered in order to isolate deeper mass influences and visualize the asthenospheric upwelling previously described from magnetotelluric data. Moho inversion yields a crustal attenuation at 36- to 32-km depth coinciding with T e below 20-km depth and a shallow T c (≤15-km depth) at the site where Geoid positive undulation was calculated. Finally, surface analysis allowed defining a topographic swell, compatible with the dimensions of the identified magnetic anomaly, where the main rivers deviated, potentially due to a recent base level change. Fil: Astort, Ana. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; Argentina Fil: Colavitto, Bruno. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; Argentina Fil: Sagripanti, Lucía. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; Argentina Fil: Garcia, Hector Pedro Antonio. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan; Argentina Fil: Echaurren Gonzalez, Andres. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; Argentina Fil: Soler, Santiago Rubén. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan; Argentina Fil: Ruíz, F.. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto Geofísico Sismológico Volponi; Argentina Fil: Folguera Telichevsky, Andres. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; Argentina

A comparison of kriging and moving window kriging (MWK) on a sphere is performed on GNSS/levelling data. The study was to give the answer on whether there is a significant gain in prediction accura...

The Global Navigational Satellite Systems, particularly the Global Positioning System has emerged as state of the art technology for providing precise horizontal and vertical location of points on surface of the earth. The vertical location is with respect to the Reference spheroid and known as ellipsoidal height. However in most of the application areas the heights considered are the orthometric heights (Mean Sea Level heights) with respect to the Geoid. The GPS-derived ellipsoidal heights are converted to corresponding orthometric heights using either a global or a local geoid model. Geoid model is a mathematical relation between the geoidal separation (N) and the horizontal location of a point. The accuracy of the conversion of ellipsoidal heights to orthometric heights depends on the accuracy of the geoid model. The objective of this study is to develop a local geoid model for a region of about 100 × 100 km2 area in Botswana in order to assess the accuracy of orthometric heights obtained from ellipsoidal heights. The geometric method is used for computation of the geoidal separation of control points from available orthometric heights and thereafter these points are used along with their horizontal coordinates and the geoidal separation to develop a surface model using a second degree polynomial as well as a TIN model. From the study it appears that an accuracy of about 20 cm in orthometric heights can be achieved by employing suitable number of well planned control points and an appropriate mathematical model in development of the geoid model.

Global geopotential models (GGMs) are vital in computing global geoid undulations heights. Based on the ellipsoidal height by Global Navigation Satellite System (GNSS) observations, the accurate orthometric height can be calculated by adding precise and accurate geoid undulations model information. However, GGMs also provide data from the satellite gravity missions such as GRACE, GOCE and CHAMP. Thus, this will assist to enhance the global geoid undulations data. A statistical assessment has been made between geoid undulations derived from 4 GGMs and the airborne gravity data provided by Department of Survey and Mapping Malaysia (DSMM). The goal of this study is the selection of the best possible GGM that best matches statistically with the geoid undulations of airborne gravity data under the Marine Geodetic Infrastructures in Malaysian Waters (MAGIC) Project over marine areas in Sabah. The correlation coefficients and the RMS value for the geoid undulations of GGM and airborne gravity data were computed. The correlation coefficients between EGM 2008 and airborne gravity data is 1 while RMS value is 0.1499.In this study, the RMS value of EGM 2008 is the lowest among the others. Regarding to the statistical analysis, it clearly represents that EGM 2008 is the best fit for marine geoid undulations throughout South China Sea.

Assuming that the long-wavelength geoid and topography of Venus are supported by both mantle convection and Airy isostasy, we propose a method to separate the dynamic and isostatic components of the Venusian gravity and topography with the aid of the dynamic admittance from numerical models of mantle convection and the isostatic admittance from an Airy isostatic model. The global crustal thickness is then calculated based on the isostatic component of the gravity and topography. The results show that some highland plateaus such as Ishtar Terra and Ovda Regio have thick crust, which are largely supported by isostatic compensation. Other highland plateaus such as Thetis and Phoebe Regiones appear to have superimposed contributions from crustal thickening and dynamic support. Volcanic rises such as Atla and Beta Regiones have thin crust, which is consistent with the postulation that these volcanic rises are mainly the products of dynamic uplift caused by mantle plumes.

It is investigated to what extent EGM96 affects the accuracy of digital elevation model (DEM) produced from the shuttle radar topography mission (SRTM). Global and regional analysis of EGM96 compared with EGM2008 indicate that locally there are large differences distorting to the accuracy level of SRTM DEM. In the absolute sense, the overall geoid differences throughout arc-degree tiles reach −5 m in the northeast and 2–3 m in the southern parts of Turkey. A numerical investigation over the test profiles of 200–700 km length running at various directions proves that a possible vertical datum change from EGM96 to EGM2008 yields systematically more accurate height information with an improvement of up to 2.5 m. A GPS-levelling traverse of about 900 km length points out some key patterns of this recovery. Consequently, a correction for the present version of SRTM DEM should be considered in critical implementations of Earth sciences like geoid or water flow modelling, especially for areas where EGM96 shows w...

The lithospheric structure of ancient cratons provides important constraints on models relating to tectonic evolution and mantle dynamics. Here we present the 3D lithospheric structure of the North China Craton (NCC) from a joint inversion of gravity, geoid and topography data. The NCC records a prolonged history of Archean and Paleoproterozoic accretion of crustal blocks through subduction and collision building the cratonic architecture, which was subsequently differentially destroyed during Mesozoic through extensive magmatism. The thermal structure obtained in our study is considered to define the lithosphere-asthenosphere boundary (LAB) of the NCC, and reflects the density variations within the mantle lithosphere. Employing the Moho depths from deep seismic sounding profiles for the inversion, and based on repeated computations using different parameters, we estimate the Moho depth, LAB depth and average crustal density of the craton. The Moho depth varies from 28 to 50 km and the LAB depth varies from 105 to 205 km. The LAB and Moho show concordant thinning from West to East of the NCC. The average crustal density is 2870 kg m − 3 in the western part of the NCC, higher than that in the eastern part (2750 kg m − 3 ). The results of joint inversion in our study yielded LAB depth and lithospheric thinning features similar to those estimated from thermal and seismic studies, although our results show different depth and variations in the thickness. The lithosphere gently thins from 145 to 105 km in the eastern NCC, where as the thinning is much less pronounced in the western NCC with average depth of about 175 km. The joint inversion results in this study provide another perspective on the lithospheric structure from the density properties and corresponding geophysical responses in an ancient craton.

According to the decision of IAG Reference Frame Sub-commission for Europe (EUREF) the EVRF2007 solution as the vertical reference has to be deployed in EU countries.The new height system LAS-2000,5 had been enacted as the European Vertical Reference System‘s EVRF2007 realization in Latvia and the new geoid model LV‘14 had been introduced by Latvian authority Latvian Geospatial Information Agency. However, the appreciation of the quality of quasi-geoid model LV‘14 is rather contradictious among the users in Latvia. The independent estimate and comparison of the two Latvian geoid models developed till now has been performed by the Institute of Geodesy and Geoinformatics. Previous geoid model LV98 which was developed for Baltic-1977 height system almost 20 years ago is outdated now. Preparatory actions described in order to fulfil the task of comparison the geoids in two different height systems. The equations and transformation parameters are presented in this article for the normal height conversion from Baltic-1977 height system to the Latvian realization named LAS-2000,5. The comparison is performed of both Latvian quasigeoid models – the new one LV‘14 and previous LV98. The quality of both models estimated by controlling the geoid heights at the properly densified GNSS/levelling network sites. The distribution of discrepancies in comparison with normal distribution N(x,μ,s) is depicted in corresponding figures. For LV‘14 quasi-geoid model the standard deviation of discrepancies is 3.2 cm, 75% of discrepancies x ≤ 3.2 cm. For LV98 quasigeoid model the standard deviation of discrepancies is 4.7 cm, 80% of discrepancies x ≤ 6 cm. Without doubt, the newly developed LV‘14 quasi-geoid model is of higher quality.

Since the advent of Global Navigation Satellite Systems, it has been possible to perform hydrographic survey reductions through the ellipsoid, which has the potential to simplify operations and improve bathymetric products. This technique requires a spatially continuous separation surface connecting chart datum (CD) to a geodetic ellipsoid. The Canadian Hydrographic Service (CHS), with support from the Canadian Geodetic Survey, has developed a new suite of such surfaces, termed Hydrographic Vertical Separations Surfaces, or HyVSEPs, for CD and seven tidal levels. They capture the spatial variability of the tidal datum and levels between tide gauges and offshore using semiempirical models coupling observations at tide stations with relative sea-level rise estimates, dynamic ocean model solutions, satellite altimetry, and a geoid model. HyVSEPs are available for all tidal waters of Canada, covering over seven million square kilometers of ocean and more than 200,000 kilometers of shoreline. This docu...

Radar altimetry, when corrected for tides, atmospheric forcing of the sea surface, and the effects of density variations and mean and time-variable currents, provides an along-track realization of the marine geoid. In this study we investigate whether and how such an ‘altimetric-hydrodynamic’ geoid over the North Sea can serve for validating satellite-gravimetric geoids. Our results indicate that, using ERS-2 and ENVISAT along-track altimetry and water levels from the high-resolution operational circulation model BSHcmod, we do find distinct differences in RMS fits for various state-of-the art satellite-only models (beyond degree 145 for GRACE-only, and beyond degree 185 for GOCE models) and for combined geoid models, very similar as seen in GPS-levelling validations over land areas. We find that, at spectral resolution of up to about 200, an RMS fit as low as about 7 cm can be obtained for the most recent GOCE-derived models such as GOCO05S. This is slightly above what we expect from budgeting in...