AN INTEGRATION TECHNIQUE FOR AIRBORNE GRAVITY GRADIENT MEASUREMENTS

Geophysics ◽  
1961 ◽  
Vol 26 (4) ◽  
pp. 474-479 ◽  
Author(s):  
Norman R. Paterson
Keyword(s):  
Plane Surface ◽  
Vertical Gradient ◽  
Gravity Force ◽  
Airborne Gravity ◽  
Gravity Gradient ◽  
Integration Technique ◽  
Simple Method ◽  
Gradient Measurements

For some purposes it may be desirable to work with the gravity force g rather than its vertical gradient g′. A simple method has been tested by which measurements of g′ on a plane surface can be integrated to produce values of g anywhere in space above the plane of measurement. The method appears to show promising results.

TERRAIN CORRECTIONS FOR AIRBORNE GRAVITY GRADIENT MEASUREMENTS

Geophysics ◽  
1961 ◽  
Vol 26 (4) ◽  
pp. 480-489 ◽  
Author(s):  
M. A. Chinnery
Keyword(s):  
Vertical Gradient ◽  
Airborne Gravity ◽  
Gravity Gradient ◽  
Topographic Effects ◽  
Short Account ◽  
Airborne Measurements ◽  
Practical Procedure ◽  
Complete Set ◽  
Terrain Corrections ◽  
Gradient Measurements

A method is given for the calculation of terrain corrections for airborne measurements of the vertical gradient of gravity. This includes a short account of the theory concerned, a description of the practical procedure, a complete set of numerical tables, and some examples of their application. The method described is shown to be very flexible, both with regard to aircraft height and to complexity of topography. Some discussion is also given of the magnitude of topographic effects on the gravity gradient, and it is shown that terrain corrections are in general more important here than in normal gravity work.

On: “Gravity vertical gradient measurements for the detection of small geologic and anthropogenic forms” by Z. J. Fajklewicz (GEOPHYSICS, October 1976, p. 1016–1030)

Geophysics ◽  
1977 ◽  
Vol 42 (4) ◽  
pp. 872-873
Author(s):  
Stephen Thyssen‐Bornemisza
Keyword(s):  
Research Work ◽  
Vertical Gradient ◽  
Gravity Gradient ◽  
Wind Gust ◽  
Near Surface ◽  
New Methods ◽  
Vertical Gravity Gradient ◽  
Surface Variation ◽  
Gradient Measurements ◽  
Vertical Gravity

In his paper, Fajklewicz discusses the improvement of vertical gravity gradient measurements arising from a very stable tower apparently not affected by wind gust vibration and climatic changes. Further, the lower plate where the gravity meter is resting can be changed in position to avoid possible disturbances from surface and near‐surface variation, and new methods for correcting and interpreting observed gradients over the vertical interval of about 3 m are presented. Some 1000 field stations were observed, including research work and industrial application.

VERTICAL GRADIENT OF GRAVITY ON AXIS FOR HOLLOW AND SOLID CYLINDERS

Geophysics ◽  
1966 ◽  
Vol 31 (4) ◽  
pp. 816-820 ◽  
Author(s):  
Thomas A. Elkins
Keyword(s):  
Hollow Cylinder ◽  
Sudden Change ◽  
Vertical Gradient ◽  
Outer Radius ◽  
Gravity Gradient ◽  
Gradient Effect ◽  
Vertical Gravity Gradient ◽  
Vertical Gravity ◽  
Special Case ◽  
Vertical Gradient Of Gravity

The recent interest in borehole gravimeters and vertical gravity gradient meters makes it worthwhile to analyze the simple case of the vertical gravity gradient on the axis of a hollow cylinder, simulating a borehole. From the viewpoint of potential theory the results are interesting because of the discontinuities which may occur when a vertical gradient profile crosses a sudden change in density. Formulas for the vertical gradient effect are given for observations above, inside, and below a hollow cylinder and a solid cylinder. The special case of an infinitely large outer radius for the cylinders is also considered, leading to formulas for the vertical gradient effect inside a borehole on its axis and inside a horizontal slab. Some remarks are made on the influence of the shape of a buried vertical gradient meter on the correction factor for changing the meter reading to density.

scholarly journals Application of curvatures and Poisson’s relation to airborne gravity gradient data in oil exploration

2013 ◽  
Vol 2013 (1) ◽  
pp. 1-4
Author(s):  
Carlos Cevallos ◽  
Peter Kovac ◽  
Sharon J. Lowe
Keyword(s):  
Airborne Gravity ◽  
Gravity Gradient ◽  
Oil Exploration

scholarly journals Estimation of Near-Ground Propagation Conditions Using Radar Ground Echo Coverage

2011 ◽  
Vol 28 (2) ◽  
pp. 165-180 ◽  
Author(s):  
Shinju Park ◽  
Frédéric Fabry
Keyword(s):  
Spatial Resolution ◽  
Temporal Resolution ◽  
Vertical Gradient ◽  
Simple Method ◽  
Radar Observations ◽  
Beam Bending ◽  
Radar Measurements ◽  
Temporal And Spatial ◽  
Ground Echoes

Abstract The vertical gradient of refractivity (dN/dh) determines the path of the radar beam; namely, the larger the negative values of the refractivity gradient, the more the beam bends toward the ground. The variability of the propagation conditions significantly affects the coverage of the ground echoes and, thus, the quality of the scanning radar measurements. The information about the vertical gradient of refractivity is usually obtained from radiosonde soundings whose use, however, is limited by their coarse temporal and spatial resolution. Because radar ground echo coverage provides clues about how severe the beam bending can be, we have investigated a method that uses radar observations to infer propagation conditions with better temporal resolution than the usual soundings. Using the data collected during the International H2O Project (IHOP_2002), this simple method has shown some skill in capturing the propagation conditions similar to these estimated from soundings. However, the evaluation of the method has been challenging because of 1) the limited resolution of the conventional soundings in time and space, 2) the lack of other sources of data with which to compare the results, and 3) the ambiguity in the separation of ground from weather echoes.

Microgravimetric and gravity gradient techniques for detection of subsurface cavities

Geophysics ◽  
1984 ◽  
Vol 49 (7) ◽  
pp. 1084-1096 ◽  
Author(s):  
Dwain K. Butler
Keyword(s):  
Case History ◽  
Vertical Gradient ◽  
Gravity Gradient ◽  
Horizontal Gradient ◽  
Shallow Subsurface ◽  
Gradient Profile ◽  
First Case ◽  
Profile Line ◽  
Cavity System ◽  
Subsurface Cavities

Microgravimetric and gravity gradient surveying techniques are applicable to the detection and delineation of shallow subsurface cavities and tunnels. Two case histories of the use of these techniques to site investigations in karst regions are presented. In the first case history, the delineation of a shallow (∼10 m deep), air‐filled cavity system by a microgravimetric survey is demonstrated. Also, application of familiar ring and center point techniques produces derivative maps which demonstrate (1) the use of second derivative techniques to produce a “residual” gravity map, and (2) the ability of first derivative techniques to resolve closely spaced or complex subsurface features. In the second case history, a deeper (∼ 30 m deep), water‐filled cavity system is adequately detected by a microgravity survey. Results of an interval (tower) vertical gradient survey along a profile line are presented in the second case history; this vertical gradient survey successfully detected shallow (<6 m) anomalous features such as limestone pinnacles and clay pockets, but the data are too “noisy” to permit detection of the vertical gradient anomaly caused by the cavity system. Interval horizontal gradients were determined along the same profile line at the second site, and a vertical gradient profile is determined from the horizontal gradient profile by a Hilbert transform technique. The measured horizontal gradient profile and the computed vertical gradient profile compare quite well with corresponding profiles calculated for a two‐dimensional model of the cavity system.

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