scholarly journals Determination of the Selected Gravity Field Functionals by the GGI Method: A Case Study of the Western Carpathians Area

2020 ◽  
Vol 10 (21) ◽  
pp. 7892
Author(s):  
Marek Trojanowicz ◽  
Magdalena Owczarek-Wesołowska ◽  
Lubomil Pospíšil ◽  
Olgierd Jamroz
Keyword(s):  
Gravity Data ◽  
Strong Dependence ◽  
Western Carpathians ◽  
Gravity Inversion ◽  
Constant Density ◽  
Disturbing Potential ◽  
Digital Elevation ◽  
Detailed Assessment ◽  
Elevation Model ◽  
Available Information

In this paper, some features of the local disturbing potential model developed by the GGI method (based on Geophysical Gravity Inversion) were analyzed. The model was developed for the area of the Western Carpathians covering the Polish–Slovak border. A detailed assessment of the model’s property was made regarding the accuracy of the disturbing potential values (height anomalies), gravity values, complete Bouguer anomalies (CBA), and differences between geoid undulations and height anomalies (N−ζ). Obtained accuracies of the GGI quasigeoid model (in terms of standard deviation of the residuals to the reference quasigeoid models) were at the level of ±2.2 cm for Poland and ±0.9 cm for the Slovak area. In terms of gravity, there was shown dependence of the accuracy of the GGI model on the digital elevation model (DEM) resolution, the point height, the density of gravity data used, and used reference density of topography model. The best obtained results of gravity prediction were characterized by an error of approximately 1 mGal. The GGI approach were compared with classical gravity prediction methods (using CBA and topographic-isostatic anomalies supported by Kriging prediction), getting very similar results. On the basis of the GGI model, CBA and differences (N−ζ) were also determined. The strong dependence of resolution of the CBA model obtained by GGI approach, on the size of the constant density zones, has been demonstrated. This significantly reduces the quality of such a model. The crucial importance of the topographic masses density model for both determined values (CBA and (N−ζ)) was also indicated. Therefore, for determining these quantities, all available information on topographic mass densities should be used in modelling.

Precise computation of the direct and indirect topographic effects of Helmert's 2nd method of condensation using SRTM30 digital elevation model

2011 ◽  
Vol 1 (4) ◽  
pp. 305-312 ◽  
Author(s):  
Y. Wang
Keyword(s):  
Standard Deviation ◽  
Digital Elevation Model ◽  
Outer Zone ◽  
Mean Value ◽  
Constant Density ◽  
Topographic Effects ◽  
Topographic Effect ◽  
Digital Elevation ◽  
The Mean ◽  
Elevation Model

Precise computation of the direct and indirect topographic effects of Helmert's 2nd method of condensation using SRTM30 digital elevation modelThe direct topographic effect (DTE) and indirect topographic effect (ITE) of Helmert's 2nd method of condensation are computed using the digital elevation model (DEM) SRTM30 in 30 arc-seconds globally. The computations assume a constant density of the topographic masses. Closed formulas are used in the inner zone of half degree, and Nagy's formulas are used in the innermost column to treat the singularity of integrals. To speed up the computations, 1-dimensional fast Fourier transform (1D FFT) is applied in outer zone computations. The computation accuracy is limited to 0.1 mGal and 0.1cm for the direct and indirect effect, respectively.The mean value and standard deviation of the DTE are -0.8 and ±7.6 mGal over land areas. The extreme value -274.3 mGal is located at latitude -13.579° and longitude 289.496°, at the height of 1426 meter in the Andes Mountains. The ITE is negative everywhere and has its minimum of -235.9 cm at the peak of Himalayas (8685 meter). The standard deviation and mean value over land areas are ±15.6 cm and -6.4 cm, respectively. Because the Stokes kernel does not contain the zero and first degree spherical harmonics, the mean value of the ITE can't be compensated through the remove-restore procedure under the Stokes-Helmert scheme, and careful treatment of the mean value in the ITE is required.

scholarly journals Assessment of Changes in a Viewshed in the Western Carpathians Landscape as a Result of Reforestation

Land ◽  
2020 ◽  
Vol 9 (11) ◽  
pp. 430
Author(s):  
Michał Sobala ◽  
Urszula Myga-Piątek ◽  
Bartłomiej Szypuła
Keyword(s):  
Digital Elevation Model ◽  
Forest Succession ◽  
Western Carpathians ◽  
Surface Model ◽  
Digital Surface Model ◽  
Mountainous Areas ◽  
Viewshed Analysis ◽  
Digital Elevation ◽  
Elevation Model ◽  
The Impact

A viewshed analysis is of great importance in mountainous areas characterized by high landscape values. The aim of this research was to determine the impact of reforestation occurring on former pasturelands on changes in the viewshed, and to quantify changes in the surface of glades. We combine a horizontal and a vertical approach to landscape analysis. The changes in non-forest areas and the viewshed from viewpoints located in glades were calculated using historical cartographic materials and a more recent Digital Elevation Model and Digital Surface Model. An analysis was conducted using a Visibility tool in ArcGIS. The non-forest areas decreased in the period 1848–2015. The viewshed in the majority of viewpoints also decreased in the period 1848–2015. In the majority of cases, the maximal viewsheds were calculated in 1879/1885 and 1933 (43.8% of the analyzed cases), whereas the minimal ones were calculated in 2015 (almost 57.5% of analyzed cases). Changes in the viewshed range from 0.2 to 23.5 km2 with half the cases analyzed being no more than 1.4 km2. The results indicate that forest succession on abandoned glades does not always cause a decline in the viewshed. Deforestation in neighboring areas may be another factor that has an influence on the decline.

Topography of the crust–mantle interface under the Western Superior craton from gravity data

2003 ◽  
Vol 40 (10) ◽  
pp. 1307-1320 ◽  
Author(s):  
B Nitescu ◽  
A R Cruden ◽  
R C Bailey
Keyword(s):  
Gravity Data ◽  
Three Dimensional ◽  
Gravity Anomalies ◽  
Gravity Inversion ◽  
Constant Density ◽  
Inversion Algorithm ◽  
Data Set ◽  
Mantle Boundary ◽  
Refraction Seismic ◽  
Superior Craton

The Moho undulations beneath the western part of the Archean Superior Province have been investigated with a three-dimensional gravity inversion algorithm for a single interface of constant density contrast. Inversion of the complete gravity data set produces unreal effects in the solution due to the ambiguity in the possible sources of some crustal gravity anomalies. To avoid these effects a censored gravity data set was used instead. The inversion results are consistent with reflection and refraction seismic data from the region and, therefore, provide a basis for the lateral correlation of the Moho topography between parallel seismic lines. The results indicate the existence of a major linear east–west-trending rise of the Moho below the metasedimentary English River subprovince, which is paralleled by crustal roots below the granite–greenstone Uchi and Wabigoon subprovinces. This correlation between the subprovincial structure at the surface and deep Moho undulations suggests that the topography of the crust–mantle boundary is related to the tectonic evolution of the Western Superior belts. Although certain features of the crust–mantle boundary are likely inherited from the accretionary and collisional stages of the Western Superior craton, gravity-driven processes triggered by subsequent magmatism and crustal softening may have played a role in both the preservation of those features, as well as in the development of new ones.

scholarly journals Implementation of a rigorous least-squares modification of Stokes’ formula to compute a gravimetric geoid model over Saudi Arabia (SAGEO13)

2015 ◽  
Vol 52 (10) ◽  
pp. 823-832 ◽  
Author(s):  
Ahmed Abdalla ◽  
Saad Mogren
Keyword(s):  
Saudi Arabia ◽  
Least Squares ◽  
Gravity Data ◽  
Computational Method ◽  
Gravimetric Geoid ◽  
Geoid Model ◽  
Geopotential Models ◽  
Digital Elevation ◽  
Stokes Formula ◽  
Elevation Model

A gravimetric geoid model (SAGEO13) is computed for the Kingdom of Saudi Arabia using a rigorous stochastic computational method. The computational methodology is based on a combination of least-squares (LS) modification of Stokes’ formula and the additive corrections for topographic, ellipsoidal, atmospheric, and downward continuation effects on the geoid solution. In this study, we used terrestrial gravity data, a digital elevation model (SRTM3), and seven global geopotential models (GGMs) to compute a new geoid model for Saudi Arabia. The least-squares coefficients are derived based on the optimisation of the input modification parameters. The gravimetric solution and its additive corrections are computed based on the optimum LS coefficients. Compared to GPS-levelling data, SAGEO13 shows a fit of 18 cm (RMS) after using a 4-parameter fitting model.

scholarly journals A new glacier inventory on southern Baffin Island, Canada, from ASTER data: II. Data analysis, glacier change and applications

2009 ◽  
Vol 50 (53) ◽  
pp. 22-31 ◽  
Author(s):  
Frank Paul ◽  
Felix Svoboda
Keyword(s):  
Strong Dependence ◽  
Baffin Island ◽  
Automated Classification ◽  
Inventory Data ◽  
Large Area ◽  
Glacier Inventory ◽  
Ice Caps ◽  
Digital Elevation ◽  
Elevation Model ◽  
Remote Sensing Methods

AbstractDespite its large area covered by glaciers and ice caps, detailed glacier inventory data are not yet available for most parts of Baffin Island, Canada. Automated classification of satellite data could help to overcome the data gaps. Along-track stereo sensors allow the derivation of a digital elevation model (DEM) and glacier outlines from the same point in time, and are particularly useful for this task. While part I of this study describes the remote-sensing methods, in part II we present an analysis of the derived glacier inventory data for 662 glaciers and an application to glacier volume and volume-change calculations. Among other things, the analysis reveals a mean glacier elevation of 990 m, with a weak dependence on aspect and a close agreement of the arithmetic mean with the statistical mean elevation as derived from the DEM. A strong scatter of mean slope is observed for glaciers <1 km2, and the derived glacier thickness differs by a factor of two for glaciers of the same size. For the period from about 1920 to 2000 the relative area change is –12.5% (264 glaciers), with a strong dependence on glacier size. Mean mass loss as derived from volume changes is about –0.15 mw.e. a–1.

scholarly journals The first complete glacier inventory for the whole of Greenland

2012 ◽  
Vol 6 (4) ◽  
pp. 2399-2436 ◽  
Author(s):  
P. Rastner ◽  
T. Bolch ◽  
N. Mölg ◽  
H. Machguth ◽  
F. Paul
Keyword(s):  
Strong Dependence ◽  
Ice Sheet ◽  
Climate Change Impacts ◽  
Watershed Analysis ◽  
Digital Elevation ◽  
User Communities ◽  
Baseline Information ◽  
Mapping Techniques ◽  
Elevation Model

Abstract. Glacier inventories provide important baseline information for the determination of water resources, glacier-specific changes in area and volume, climate change impacts, and the past, potential and future contribution of glaciers to sea-level rise. Though heavily glacierized and thus highly relevant for all of the above points, such an inventory of all local glaciers and icecaps (GIC) was not available so far for Greenland. Here we present the details and results of our inventory, that has been compiled from more than 70 Landsat scenes mostly acquired between 1999 and 2002 using semi-automated multispectral mapping techniques. A digital elevation model (DEM) was used to derive drainage divides from watershed analysis and topographic parameters for each glacier entity. We assigned to each entity one of three connectivity levels (CL0, CL1, CL2; i.e. no, weak, and strong connection) with the ice sheet to distinguish the local GIC from the ice sheet and its outlet glaciers and to serve the specific needs of different user communities. All GIC larger 0.05 km2 include ~20 300 entities (of which 900 are marine terminating), covering an area of 129 983 ± 4029 km2, or 89 273 ± 2767 km2 without the CL2 GIC. The latter is about 50% more than according to all previous estimates. Glaciers smaller 0.5 km2 contribute only 1.5% to the total area but more than 50% (11 000) to the total number. In contrast, the 25 largest GIC (>500 km2) contribute 28% to the total area, but only 0.1% to the total number. Most of the ice was located at elevations around 1000 m, except in the eastern sector with elevation arround 1700 m. In addition, a strong dependence of the median elevation to the distance from the ocean was found, but only a weak dependence on aspect. All data will be made available in the Global Land Ice Measurement from Space (GLIMS) glacier database.

DETECTION OF GROSS ERRORS IN THE GRAVIMETRIC DATABASE OF THE RIO GRANDE DO SUL STATE

2012 ◽  
Vol 30 (3) ◽  
Author(s):  
Marilei Bender Xavier ◽  
Silvia Beatriz Alves Rolim
Keyword(s):  
Gravity Data ◽  
Bouguer Anomaly ◽  
Rio Grande ◽  
Shuttle Radar Topography Mission ◽  
Rio Grande Do Sul ◽  
Digital Elevation ◽  
Anomaly Map ◽  
Bouguer Anomaly Map ◽  
Elevation Model ◽  
Gravity Recovery

Since 1950, ground gravity data of the Rio Grande do Sul State (RS), Brazil, have been systematically collected by the Department of Geodesy of the Universidade Federal do Rio Grande do Sul (UFRGS) and other institutions in a total of 7.218 points. This paper proposes three methods for detection of gross errors in this database, based on: 1) the digital elevation model of Shuttle Radar Topography Mission (SRTM), 2) the Gravity Recovery and Climate Experiment (GRACE), and 3) the interpolated observations of ground gravity observations (Bouguer anomaly). The 1st method identified 217 points of altimetry, representing 3.00% of the database. The 2nd identified 645 points of gravity observations, representing 8.93% of the database. The3 rd method identified 60 points of land gravimetric observations, representing 0.83% of the database. The criterion to eliminate the observations was based on the recognition of coincident outliers in, at least, 2 methods. The matching points of coarse errors among altimetry, gravity and Bouguer anomaly were grouped in 177 points, representing 2.45% of the database. These points were considered gross errors and were erased from the database. After cleaning the database, we focused in the preliminary interpretation of the Bouguer anomaly map of the RS, recognizing a direct association of the main regional geologic units with four well-defined geophysical domains.

scholarly journals Orthometric Corrections Using Gridded Gravity Data Derived from Digital Elevation Model

2022 ◽  
Vol 34 (x) ◽  
pp. 1
Author(s):  
Hong Sool Lee ◽  
Kwang Bae Kim ◽  
Chang Uk Woo ◽  
Hong Sik Yun
Keyword(s):  
Digital Elevation Model ◽  
Gravity Data ◽  
Digital Elevation ◽  
Elevation Model

Mapping Geologic Structures from Gravity and Digital Elevation Model in the Ziway-Shala Lakes Basin; central Main Ethiopian Rift

2020 ◽  
Author(s):  
Hailemichael Kebede ◽  
Abera Alemu ◽  
Dessie Nedaw
Keyword(s):  
Digital Elevation Model ◽  
Gravity Data ◽  
Surface Structures ◽  
Ethiopian Rift ◽  
Main Ethiopian Rift ◽  
Near Surface ◽  
Subsurface Structures ◽  
Digital Elevation ◽  
Moho Depths ◽  
Elevation Model

Abstract This study attempts to delineate subsurface lineaments for the tectonically and volcanically active region of the Ziway-Shala Lakes basin, central Main Ethiopian rift. Most of the previously mapped subsurface structures in the region under consideration focus on delineating crustal structures thicknesses and Moho depths undulations. Moreover, near-surface structures in the same region were mapped using analysis of Digital Elevation Model image data. On the other hand, there are few studies that have targeted in mapping geologic structures lying at intermediate depth levels between the shallower and deeper Earth. The objective of this research is thus to map the subsurface geologic structures/lineaments to an average depth of 3 km (crystalline basement layer depth) from surface using gravity data. These investigation results are validated by Digital Elevation Model extracted lineaments. Filtering techniques including derivative filters, upward-continuation and line module algorithm of PCI Geomatica are used to extract the gravity and topographic lineaments of the region. Orientation analyses of these subsurface and surface lineaments are made using line direction histogram of the QGIS software. Accordingly, the gravity subsurface lineaments mapped in this study are found to be dominantly oriented in the NNW-SSE to NW-SE and E-W direction on average. These results appear to be contrary to the NNE-SSW to NE-SW trending surface geologic structure mapped on the bases of actual field observation carried out by previous researchers and automatically extracted lineaments based on Digital Elevation Models data considered in this research. The subsurface lineaments mapped using gravity data coincide with the orientation of pre-existing subsurface structures crossing the rift orthogonally. These structural lineaments which are considered to be masked in the subsurface coincide with the orientation of the Mesozoic Ogaden rift as compared to the overlying surface structures which appear to coincide with the orientation of the Cenozoic Main Ethiopian rift.

Effect of topographic potential difference and gravity correction on the geoid-quasigeoid separation

2020 ◽  
Author(s):  
Yan Ming Wang
Keyword(s):  
Standard Deviation ◽  
Gravity Data ◽  
Grid Size ◽  
Potential Difference ◽  
Terrestrial Gravity ◽  
Mountainous Regions ◽  
Digital Elevation ◽  
Topographic Potential ◽  
Elevation Model ◽  
Geoid Computation

&lt;p&gt;The effect of the topographic potential difference and the gravity correction on the geoid-quasigeoid separation are usually ignored in numerical computations. Those effects are computed in a mountainous Colorado region by using the digital elevation model SRTM v4.1 and terrestrial gravity data. The effects are computed at 1&amp;#8242;X1&amp;#8242; grid size in the region. The largest effect is the topographic potential difference. It reaches a maximum of 19.0 cm with a standard deviation of 1.8 cm over the whole region. The gravity correction is smaller, but it still reaches a maximum of 3.0 cm with a standard deviation 0.3 cm for the whole region. The combined (ignored) effect ranges from -12.2 to 20.0 cm, with a standard deviation of 1.8 cm for the region. This numerical computation shows that the ignored terms must be taken into account for cm-geoid computation in mountainous regions.&lt;/p&gt;

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