A sloping wedge technique for calculating gravity terrain corrections

Geophysics ◽  
1991 ◽  
Vol 56 (7) ◽  
pp. 1061-1063 ◽  
Author(s):  
L. J. Barrows ◽  
J. D. Fett
Keyword(s):  
High Precision ◽  
Field Data ◽  
Open Space ◽  
Gravity Station ◽  
Topographic Features ◽  
Original Field ◽  
Rugged Topography ◽  
Terrain Corrections ◽  
Wedge Technique

Gravity terrain corrections account for the upward pull of topographic features which are higher than a gravity station (hills) and the lack of downward pull from open space which is lower than the station (valleys). In areas of rugged topography or in high precision surveys, the magnitude of the terrain corrections can be comparable to the anomalies being sought and the uncertainties in the terrain corrections can limit the accuracy of the survey. Also, calculating the corrections can require more time and effort than gathering the original field data. Even if terrain corrections are not made, it is necessary to show that their omission does not compromise the integrity of the survey.

Improvement of the conic prism model for terrain correction in rugged topography

Geophysics ◽  
1981 ◽  
Vol 46 (7) ◽  
pp. 1054-1056 ◽  
Author(s):  
Raymond J. Olivier ◽  
Réjean G. Simard
Keyword(s):  
Gravity Anomalies ◽  
Terrain Correction ◽  
Field Calculation ◽  
Bouguer Gravity ◽  
New Model ◽  
Gravity Station ◽  
Rugged Terrain ◽  
Rugged Topography ◽  
Terrain Corrections ◽  
Prism Model

Terrain corrections for Bouguer gravity anomalies are generally obtained from topographic models represented by flat‐topped compartments of circular zones, utilizing the so‐called Hayford‐Bowie (1912), or Hammer’s (1939) method. Some authors have introduced improved relief models for taking uniform slope into consideration (Sandberg, 1958; Kane, 1962; Takin and Talwani, 1966; Campbell, 1980). We present a new model that increases the accuracy of the calculation of terrain correction close to the gravity station in rugged terrain, especially when conventional templates with few zones are used in field calculation.

Gravity terrain corrections calculated using digital elevation models

Geophysics ◽  
1990 ◽  
Vol 55 (1) ◽  
pp. 102-106 ◽  
Author(s):  
Allen H. Cogbill
Keyword(s):  
High Precision ◽  
The Other ◽  
Mountainous Areas ◽  
Data Set ◽  
Gravity Station ◽  
Digital Terrain ◽  
Terrain Effects ◽  
Digital Elevation ◽  
Gravity Measurements ◽  
Terrain Corrections

Corrections for terrain effects are required for virtually all gravity measurements acquired in mountainous areas, as well as for high‐precision surveys, even in areas of low relief. Terrain corrections are normally divided into two parts, one part being the correction for terrain relatively close to the gravity station (the “inner‐zone” correction) and the other part being the correction for more distant, say, >2 km, terrain. The latter correction is normally calculated using a machine procedure that accesses a digital‐terrain data set. The corrections for terrain very close to the gravity station are done manually using Hammer’s (1939) procedures or a similar method, are guessed in the field, or simply are neglected. Occasionally, special correction procedures are used for the inner‐zone terrain corrections (e.g., LaFehr et al., 1988); but such instances are uncommon.

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 A High-Precision Magnetic-Assisted Heading Angle Calculation Method Based on a 1D Convolutional Neural Network (CNN) in a Complicated Magnetic Environment

Micromachines ◽  
2020 ◽  
Vol 11 (7) ◽  
pp. 642
Author(s):  
Guanghui Hu ◽  
Hong Wan ◽  
Xinxin Li
Keyword(s):  
Neural Network ◽  
Convolutional Neural Network ◽  
High Precision ◽  
Geomagnetic Field ◽  
Field Data ◽  
Time Window ◽  
Magnetic Data ◽  
Navigation Systems ◽  
Pedestrian Navigation ◽  
Heading Angle

Due to its widespread presence and independence from artificial signals, the application of geomagnetic field information in indoor pedestrian navigation systems has attracted extensive attention from researchers. However, for indoors environments, geomagnetic field signals can be severely disturbed by the complicated magnetic, leading to reduced positioning accuracy of magnetic-assisted navigation systems. Therefore, there is an urgent need for methods which screen out undisturbed geomagnetic field data for realizing the high accuracy pedestrian inertial navigation indoors. In this paper, we propose an algorithm based on a one-dimensional convolutional neural network (1D CNN) to screen magnetic field data. By encoding the magnetic data within a certain time window to a time series, a 1D CNN with two convolutional layers is designed to extract data features. In order to avoid errors arising from artificial labels, the feature vectors will be clustered in the feature space to classify the magnetic data using unsupervised methods. Our experimental results show that this method can distinguish the geomagnetic field data from indoors disturbed magnetic data well and further significantly improve the calculation accuracy of the heading angle. Our work provides a possible technical path for the realization of high-precision indoor pedestrian navigation systems.

TERRAIN CORRECTIONS FOR AN INCLINED PLANE IN GRAVITY COMPUTATIONS

Geophysics ◽  
1958 ◽  
Vol 23 (4) ◽  
pp. 701-711 ◽  
Author(s):  
C. H. Sandberg
Keyword(s):  
Inclined Plane ◽  
Gravity Station ◽  
Terrain Effect ◽  
Terrain Corrections ◽  
Inclined Planes

In many instances an inclined‐plane approximation represents more accurately the terrain near a gravity station than does the conventional block‐cylinder approximation. Combinations of the terrain effect of inclined planes through various terrain zones, as represented in the accompanying tables, can be used to approximate easily and quickly such familiar land forms as valleys, ridges, and hillsides.

scholarly journals Ørsted satellite captures high-precision geomagnetic field data

Eos ◽  
2001 ◽  
Vol 82 (7) ◽  
pp. 81-88 ◽  
Author(s):  
Torsten Neubert ◽  
M. Mandea ◽  
G. Hulot ◽  
R. von Frese ◽  
F. Primdahl ◽  
...  
Keyword(s):  
High Precision ◽  
Geomagnetic Field ◽  
Field Data

scholarly journals High Precision Terrain Corrections for Next Generation Airborne Gravity Data

2015 ◽  
Vol 2015 (1) ◽  
pp. 1-4
Author(s):  
T. Aravanis ◽  
M. Grujic ◽  
J. Paine ◽  
R. J. Smith
Keyword(s):  
High Precision ◽  
Gravity Data ◽  
Airborne Gravity ◽  
Next Generation ◽  
Terrain Corrections

Gravimetric terrain corrections in western Canada

1983 ◽  
Vol 20 (2) ◽  
pp. 259-265 ◽  
Author(s):  
J. A. R. Blais ◽  
G. D. Lodwick ◽  
R. Ferland
Keyword(s):  
Western Canada ◽  
Gravimetric Measurements ◽  
Optimal Technique ◽  
Rugged Topography ◽  
Terrain Corrections ◽  
Theoretical Results

Terrain corrections for gravimetric measurements have been studied in terms of accuracy requirements and automated computations. Geodetic and geophysical applications in western Canada have been considered specifically because of complications arising from the rugged topography. Comparing the computation methods of Nagy and Mathisen in relation to the theoretical results, the former is shown to be more reliable with simulated accidented topography. Other approaches are also briefly discussed and general recommendations are made for an optimal technique to compute gravimetric terrain corrections in western Canada.

scholarly journals Are phonological features of roots in syntax? Evidence from Guébie

2015 ◽  
Author(s):  
Hannah Sande
Keyword(s):  
Field Data ◽  
Title Page ◽  
Phonological Features ◽  
Third Person ◽  
Original Field

<div class="page" title="Page 1"><div class="layoutArea"><div class="column"><p><span>Based on original field data, I demonstrate that in Guébie (Kru, Niger-Congo), third person pronouns </span><span>phonologically </span><span>resemble their antecedents. This system, along with other phonologically determined agreement systems, pose problems for our traditional Y-model of grammar, which assumes that phonological features are not present in the syntax (cf. DM, Marantz 1995), thus morphosyntactic processes like agreement should not be able to access phonological features. </span></p><p><span>Here I address the question of whether phonologically determined agreement systems can be modeled without requiring syntax to be sensitive to phonological features. To do this I argue that pronouns select for an NP complement (cf. Elbourne 2001), where the pronoun enters into an agree relation with its NP complement. When spelled out, the morphologically agreeing heads must be phonologically similar, and this overt agreement licenses ellipsis of the NP. </span></p></div></div></div>

A method to compute terrain corrections for gravimeter stations using a digital elevation model

Geophysics ◽  
2001 ◽  
Vol 66 (4) ◽  
pp. 1110-1115 ◽  
Author(s):  
J. Garca‐Abdeslem ◽  
B. Martn‐Atienza
Keyword(s):  
Numerical Methods ◽  
Digital Elevation Model ◽  
Mass Density ◽  
Model Solution ◽  
Gravitational Attraction ◽  
Gravity Effect ◽  
Gravity Station ◽  
Digital Elevation ◽  
Terrain Corrections ◽  
Elevation Model

A description is given of a method to compute the terrain corrections for a gravity survey using a digital elevation model. This method is based upon a new forward model solution to compute the gravity effect due to a rectangular prism of uniform mass density that is flat at its base but has a nonflat top. The gravitational attraction of such a prism is evaluated at the gravity station locations by combining analytic and numerical methods of integration. Two simple synthetic examples are provided that show the accuracy of this numerical method, and its performance is illustrated in a field example.

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