Gravity measurements and terrain corrections using a digital terrain model in the NW Himalaya

1998 ◽  
Vol 24 (10) ◽  
pp. 1009-1020 ◽  
Author(s):  
Paramesh Banerjee
Keyword(s):  
Digital Terrain Model ◽  
Nw Himalaya ◽  
Terrain Model ◽  
Digital Terrain ◽  
Gravity Measurements ◽  
Terrain Corrections

The generalized gravity anomaly: Endoscopic microgravity

Geophysics ◽  
1991 ◽  
Vol 56 (5) ◽  
pp. 712-723 ◽  
Author(s):  
J. Lakshmanan
Keyword(s):  
Underground Structure ◽  
Bouguer Anomaly ◽  
Digital Terrain Model ◽  
Gravity Anomalies ◽  
Underground Structures ◽  
Terrain Model ◽  
Digital Terrain ◽  
Generalized Inversion ◽  
Gravity Measurements ◽  
The One

Various underground 3-D gravity surveys have necessitated a generalization of the usual gravity corrections and of the Bouguer anomaly. The method presented here compares raw, time‐dependent gravity measurements, to a model’s total theoretical field, including known fields: moon, sun, 1967 Reference Ellipsoid, oceans; partially known fields: due to a single digital terrain model of known geometry but of unknown densities; and unknown fields due to underground structures of unknown shapes and of unknown densities. For a single‐density model, the corresponding first‐degree residual is close in concept to the Bouguer anomaly. To best determine underground structure, generalized inversion then leads to determination of the one or several densities and of one or several “regional” parameters, which minimize residuals. The suggested method is mainly advantageous in special types of gravity surveys, such as rugged terrain, or in the case of underground surveys, where conventional corrections, with a preset terrain density can possibly lead to substantial errors. Two field examples are developed (1) the Cheops pyramid survey, where the processing of gravity measurements inside, above, and around the pyramid led to an evaluation of the structure’s overall density and of density changes in the structure; and (2) the Coche hydroelectric tunnel in the Alps, where the method leads to a 3-D model explaining the very strong gravity anomalies observed in the tunnel and on the mountain above it.

scholarly journals The estimation of errors in calculated terrain corrections in the Tatra Mountains

2010 ◽  
Vol 40 (4) ◽  
pp. 323-350 ◽  
Author(s):  
Pavol Zahorec ◽  
Roman Pašteka ◽  
Juraj Papčo
Keyword(s):  
Digital Terrain Model ◽  
Tatra Mountains ◽  
Mountainous Areas ◽  
Bouguer Anomalies ◽  
Terrain Model ◽  
Digital Terrain ◽  
Terrain Models ◽  
Terrain Corrections ◽  
The Tatra Mountains ◽  
Shed Light

The estimation of errors in calculated terrain corrections in the Tatra Mountains In general, calculation of terrain corrections can be a substantial source of errors in evaluating Bouguer anomalies, especially in rugged mountainous areas like the Tatra Mountains where we also get the largest values of the terrain corrections as such. It is then natural that analysis of their calculations in this area can shed light on the magnitude of correction-related errors within the whole Slovak territory. In the framework of our analysis we have estimated the effect of different computing approaches as well as the influence of accuracy of the inputs, i.e. the heights and positions of the measuring points, together with the used digital terrain models. For the sake of testing the computer programs which are currently in use, we have also substituted the real terrain by synthetic topography. We found that among the concerned constituents the most important factor is the used digital terrain model and its accuracy. The possible model-caused errors can exceed 10 mGal in the Tatra Mountains (for the density of 2.67 g.cm-3).

GRAVITY TERRAIN CORRECTIONS USING MULTIQUADRIC EQUATIONS

Geophysics ◽  
1976 ◽  
Vol 41 (2) ◽  
pp. 266-275 ◽  
Author(s):  
Douglas H. Krohn
Keyword(s):  
Linear System ◽  
Numerical Integration ◽  
Digital Computer ◽  
Digital Terrain Model ◽  
Computer Method ◽  
Gravity Station ◽  
Terrain Model ◽  
Digital Terrain ◽  
Rugged Topography ◽  
Terrain Corrections

A digital computer method of making gravity station terrain corrections has been developed that uses a linear system of multiquadric equations. This system is fitted to the points defined by square topographic compartments and the point defined by the station itself to give a mathematically described surface. The surface is a better model of the actual topography than the digital terrain model, especially near the station. Terrain correction of this surface is calculated using a simple and fast numerical integration. A theoretical example shows that the multiquadric equation method is potentially more accurate than a hand chart method for near‐station terrain corrections. Field examples in an area of rugged topography show that the method can be successfully used for actual gravity stations.

scholarly journals High-precision local gravity survey along planned motorway tunnel in the Slovak Karst

2019 ◽  
Vol 49 (2) ◽  
pp. 207-227 ◽  
Author(s):  
Pavol Zahorec ◽  
Juraj Papčo ◽  
Peter Vajda ◽  
Stanislav Szabó
Keyword(s):  
Laser Scanning ◽  
Gravity Data ◽  
Digital Terrain Model ◽  
Gravity Survey ◽  
Railway Tunnel ◽  
Bouguer Anomalies ◽  
Terrain Model ◽  
Gravity Measurements ◽  
Terrain Corrections ◽  
The Difference

Abstract Results from a detailed gravity survey realized along the planned highway tunnel in the karstic area of Slovak Karst in the eastern Slovakia are presented. Detailed gravity profiles crossed an area of rugged topography, therefore the terrain corrections played a crucial role in the gravity data processing. The airborne laser scanning technique (LiDAR) was used in order to compile a high-resolution digital terrain model (DTM) of the surrounding area and to calculate terrain corrections properly. The difference between the Bouguer anomalies calculated with an available nationwide DTM and those with new LiDAR-based model can be significant in some places as it is presented in the paper. A new method for Bouguer correction density analysis based on surface data is presented. Special underground gravity measurements in the existing nearby railway tunnel were also conducted in order to determine the mean density of the topographic rocks. The Bouguer anomalies were used to interpret lithological contacts and tectonic/karstic discontinuities.

scholarly journals The Effect of LiDAR Sampling Density on DTM Accuracy for Areas with Heavy Forest Cover

Forests ◽  
2021 ◽  
Vol 12 (3) ◽  
pp. 265
Author(s):  
Mihnea Cățeanu ◽  
Arcadie Ciubotaru
Keyword(s):  
Forest Cover ◽  
Initial Point ◽  
Ground Surface ◽  
Digital Terrain Model ◽  
Morphological Data ◽  
Sampling Density ◽  
Terrain Model ◽  
Digital Terrain ◽  
Point Density ◽  
The Impact

Laser scanning via LiDAR is a powerful technique for collecting data necessary for Digital Terrain Model (DTM) generation, even in densely forested areas. LiDAR observations located at the ground level can be separated from the initial point cloud and used as input for the generation of a Digital Terrain Model (DTM) via interpolation. This paper proposes a quantitative analysis of the accuracy of DTMs (and derived slope maps) obtained from LiDAR data and is focused on conditions common to most forestry activities (rough, steep terrain with forest cover). Three interpolation algorithms were tested: Inverse Distance Weighted (IDW), Natural Neighbour (NN) and Thin-Plate Spline (TPS). Research was mainly focused on the issue of point data density. To analyze its impact on the quality of ground surface modelling, the density of the filtered data set was artificially lowered (from 0.89 to 0.09 points/m2) by randomly removing point observations in 10% increments. This provides a comprehensive method of evaluating the impact of LiDAR ground point density on DTM accuracy. While the reduction of point density leads to a less accurate DTM in all cases (as expected), the exact pattern varies by algorithm. The accuracy of the LiDAR-derived DTMs is relatively good even when LiDAR sampling density is reduced to 0.40–0.50 points/m2 (50–60 % of the initial point density), as long as a suitable interpolation algorithm is used (as IDW proved to be less resilient to density reductions below approximately 0.60 points/m2). In the case of slope estimation, the pattern is relatively similar, except the difference in accuracy between IDW and the other two algorithms is even more pronounced than in the case of DTM accuracy. Based on this research, we conclude that LiDAR is an adequate method for collecting morphological data necessary for modelling the ground surface, even when the sampling density is significantly reduced.

scholarly journals DTM-based analysis of the spatial distribution of topolineaments

2020 ◽  
Vol 12 (1) ◽  
pp. 1185-1199
Author(s):  
Mirosław Kamiński
Keyword(s):  
Laser Scanning ◽  
Digital Terrain Model ◽  
Research Area ◽  
Tectonic Structures ◽  
Empirical Bayesian ◽  
Scanning Method ◽  
Empirical Bayesian Kriging ◽  
Terrain Model ◽  
Digital Terrain ◽  
Airborne Laser

AbstractThe research area is located on the boundary between two Paleozoic structural units: the Radom–Kraśnik Block and the Mazovian–Lublin Basin in the southeastern Poland. The tectonic structures are separated by the Ursynów–Kazimierz Dolny fault zone. The digital terrain model obtained by the ALS (Airborne Laser Scanning) method was used. Classification and filtration of an elevation point cloud were performed. Then, from the elevation points representing only surfaces, a digital terrain model was generated. The model was used to visually interpret the course of topolineaments and their automatic extraction from DTM. Two topolineament systems, trending NE–SW and NW–SE, were interpreted. Using the kernel density algorithm, topolineament density models were generated. Using the Empirical Bayesian Kriging, a thickness model of quaternary deposits was generated. A relationship was observed between the course of topolineaments and the distribution and thickness of Quaternary formations. The topolineaments were compared with fault directions marked on tectonic maps of the Paleozoic and Mesozoic. Data validation showed consistency between topolineaments and tectonic faults. The obtained results are encouraging for further research.

scholarly journals Production, Validation and Morphometric Analysis of a Digital Terrain Model for Lake Trichonis Using Geospatial Technologies and Hydroacoustics

2021 ◽  
Vol 10 (2) ◽  
pp. 91
Author(s):  
Triantafyllia-Maria Perivolioti ◽  
Antonios Mouratidis ◽  
Dimitrios Terzopoulos ◽  
Panagiotis Kalaitzis ◽  
Dimitrios Ampatzidis ◽  
...  
Keyword(s):  
Morphometric Analysis ◽  
Ad Hoc ◽  
Regional Scale ◽  
Digital Terrain Model ◽  
Relevant Information ◽  
Relative Difference ◽  
Systematic Observation ◽  
Qualitative And Quantitative ◽  
Terrain Model ◽  
Digital Terrain

Covering an area of approximately 97 km2 and with a maximum depth of 58 m, Lake Trichonis is the largest and one of the deepest natural lakes in Greece. As such, it constitutes an important ecosystem and freshwater reserve at the regional scale, whose qualitative and quantitative properties ought to be monitored. Depth is a crucial parameter, as it is involved in both qualitative and quantitative monitoring aspects. Thus, the availability of a bathymetric model and a reliable DTM (Digital Terrain Model) of such an inland water body is imperative for almost any systematic observation scenario or ad hoc measurement endeavor. In this context, the purpose of this study is to produce a DTM from the only official cartographic source of relevant information available (dating back approximately 70 years) and evaluate its performance against new, independent, high-accuracy hydroacoustic recordings. The validation procedure involves the use of echosoundings coupled with GPS, and is followed by the production of a bathymetric model for the assessment of the discrepancies between the DTM and the measurements, along with the relevant morphometric analysis. Both the production and validation of the DTM are conducted in a GIS environment. The results indicate substantial discrepancies between the old DTM and contemporary acoustic data. A significant overall deviation of 3.39 ± 5.26 m in absolute bottom elevation differences and 0.00 ± 7.26 m in relative difference residuals (0.00 ± 2.11 m after 2nd polynomial model corrector surface fit) of the 2019 bathymetric dataset with respect to the ~1950 lake DTM and overall morphometry appear to be associated with a combination of tectonics, subsidence and karstic phenomena in the area. These observations could prove useful for the tectonics, geodynamics and seismicity with respect to the broader Corinth Rift region, as well as for environmental management and technical interventions in and around the lake. This dictates the necessity for new, extensive bathymetric measurements in order to produce an updated DTM of Lake Trichonis, reflecting current conditions and tailored to contemporary accuracy standards and state-of-the-art research in various disciplines in and around the lake.

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