On: “The normal vertical gradient of gravity” by J. H. Karl (GEOPHYSICS, 48, 1011–1013, July 1983).

Geophysics ◽  
1986 ◽  
Vol 51 (7) ◽  
pp. 1505-1508 ◽  
Author(s):  
T. R. LaFehr ◽  
Kwok C. Chan
Keyword(s):  
Data Reduction ◽  
Normal Gravity ◽  
Traditional Approach ◽  
Vertical Gradient ◽  
Gravity Gradient ◽  
Average Value ◽  
Terrain Model ◽  
Vertical Gradient Of Gravity

In his reply to C. J. Swain’s (1984) discussion Karl states that no one has disagreed with his proposed (0.265 mGal/m) “average value” for the normal gravity gradient and that his global terrain model can be used to challenge the validity of the traditional approach to data reduction. Our investigations show that Karl is in error on both counts, and we hope that the following analyses will help toward a clearer understanding of this question.

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.

The normal vertical gradient of gravity

Geophysics ◽  
1983 ◽  
Vol 48 (7) ◽  
pp. 1011-1013 ◽  
Author(s):  
John H. Karl
Keyword(s):  
Gravity Field ◽  
Potential Field ◽  
Large Scale ◽  
Normal Gravity ◽  
Vertical Gradient ◽  
Original Model ◽  
Field Methods ◽  
The Earth ◽  
Vertical Gradient Of Gravity

Most gravity surveys are conducted to estimate subsurface density contrasts for one application or another. From large‐scale crustal studies to relatively small exploration surveys, it is necessary to determine in some way what the normal gravity field should be in order to identify anomalous features. The anomalies then represent deviations to be interpreted in light of the original model. It is a central limitation of potential field methods that this model, sometimes representing a so‐called “regional” field, is not unique. In the case of gravity, this model has traditionally involved geometrical approximations. It is generally assumed that variations in station elevations are small compared with the radius of the earth—an obviously excellent approximation, but one needs to be mathematically consistent.

Advantages of using the vertical gradient of gravity for 3-D interpretation

Geophysics ◽  
1993 ◽  
Vol 58 (11) ◽  
pp. 1588-1595 ◽  
Author(s):  
I. Marson ◽  
E. E. Klingele
Keyword(s):  
Gravity Data ◽  
Vertical Gradient ◽  
Three Dimensions ◽  
Gravity Gradient ◽  
Horizontal Gradient ◽  
Euler Deconvolution ◽  
Model Studies ◽  
Combined Use ◽  
Deconvolution Techniques ◽  
Vertical Gradient Of Gravity

Gravity gradiometric data or gravity data transformed into vertical gradient can be efficiently processed in three dimensions for delineating density discontinuities. Model studies, performed with the combined use of maxima of analytic signal and of horizontal gradient and the Euler deconvolution techniques on the gravity field and its vertical gradient, demonstrate the superiority of the latter in locating density contrasts. Particularly in the case of interfering anomalies, where the use of gravity alone fails, the gravity gradient is able to provide useful information with satisfactory accuracy.

OBSERVATION OF THE VERTICAL GRADIENT OF GRAVITY IN THE FIELD

Geophysics ◽  
1956 ◽  
Vol 21 (3) ◽  
pp. 771-779 ◽  
Author(s):  
Stephen Thyssen‐Bornemisza ◽  
W. F. Stackler
Keyword(s):  
Vertical Gradient ◽  
Gravity Gradient ◽  
Field Observations ◽  
Vertical Gravity Gradient ◽  
Vertical Gravity ◽  
Vertical Gradient Of Gravity

Field observations of the anomalous vertical gravity gradient were made at Houston, Texas, and over the Turner Valley structure near Calgary, Alberta, Canada. The results obtained are encouraging, but the precision of the measurements was to some extent reduced by vibrations generated in transporting the gravimeter up and down the tripod, as well as by gusts of wind.

On: “The anomalous vertical gradient of gravity” by Sigmund Hammer (GEOPHYSICS, February 1970, p. 153–157).

Geophysics ◽  
1971 ◽  
Vol 36 (1) ◽  
pp. 214-216 ◽  
Author(s):  
Stephen Thyssen‐Bornemisza
Keyword(s):  
Horizontal Plane ◽  
Vertical Gradient ◽  
Observation Point ◽  
Gravity Gradient ◽  
Vertical Gravity Gradient ◽  
Free Air ◽  
Plane Passing ◽  
Vertical Gravity ◽  
Vertical Gradient Of Gravity

The interesting analysis by Hammer seems to be founded partly on the approach of Heiskanen and Moritz (1967), in which a real gravity and a vertical gravity gradient are correlated according to the relation [Formula: see text] Here Δg denotes the free‐air anomalies on a horizontal plane passing through observation point p and [Formula: see text] is the anomaly at p, the latter representing the center of the (x, y) coordinates.

On: “The normal vertical gradient of gravity” by J. H. Karl (GEOPHYSICS, 48, 1011–1013).

Geophysics ◽  
1984 ◽  
Vol 49 (9) ◽  
pp. 1563-1563 ◽  
Author(s):  
C. J. Swain
Keyword(s):  
Sea Level ◽  
Gravity Data ◽  
Vertical Gradient ◽  
Practical Significance ◽  
Average Value ◽  
The Earth ◽  
Free Air ◽  
The Mean ◽  
Local Anomalies ◽  
Vertical Gradient Of Gravity

The implication of the author’s hypothesis, that the conventional free‐air correction factor is difficult to justify and can lead to large errors (e.g., 14 mGal from 300 m of topographic relief), would be very serious indeed for many interpretations of gravity data if it were true. He predicts a normal vertical gradient of 0.264 mGal/m near sea level, 14 percent lower than the conventional theoretical value. However, precise measurements of the free‐air gradient near sea level have been reported (Kuo et al., 1969) which differ by less than [Formula: see text] percent from the theoretical value; moreover these differences correlate with small local (isostatic) anomalies. My own observations at Leicester, England (elevation 100 m) and Nairobi (elevation 1 650 m) (made with students) also differ by less than [Formula: see text] percent from the theoretical values and again the differences correlate with small local anomalies. If these values represent the normal free‐air gradient, it would appear that the author’s analysis must be wrong. The formula he derives gives, correctly, the mean vertical gradient at some level over and within the Earth to a good approximation. This can be seen simply by considering the well‐known formulas for the gradient at a point within the Earth where the density is ρ [Formula: see text] and at a point outside the Earth [Formula: see text] and taking averages at this radius. However, the average value has no practical significance. It does not apply to any point on the Earth’s surface; it is merely a mean.

scholarly journals Penerapan Metode Diskusi Terbimbing untuk Meningkatkan Kemampuan Guru dalam Pembuatan RPP di SMKN 3 Gowa

2021 ◽  
Vol 8 (4) ◽  
pp. 534
Author(s):  
H. Karnedy Bolong
Keyword(s):  
Data Analysis ◽  
Action Research ◽  
Learning Outcomes ◽  
Data Reduction ◽  
Lesson Plans ◽  
Research Instrument ◽  
Average Value ◽  
Analysis Technique ◽  
Three Stages ◽  
Target Set

The purpose of this study was to improve the ability of teachers in making lesson plans through guided discussions at SMKN 3 Gowa. The research used is school action research which is carried out in 2. This research instrument uses tests and non-tests. The data analysis technique used was descriptive which was carried out through three stages, namely: data reduction, data exposure, and inference. The results of this study indicate that the data in the first cycle with an average value of 59.7 with completeness of 43.3% and the ability of teachers to use lesson plans by 50% where these results have not reached the target set, then the action is taken in Cycle II by doing improvement of learning and lesson plans, so that learning outcomes increase to 72.0%. So it can be concluded that the guided discussion method can improve the ability of teachers in making lesson plans at SMKN 3 Gowa.

scholarly journals Reduction Method for Mobile Laser Scanning Data

2018 ◽  
Vol 7 (7) ◽  
pp. 285 ◽  
Author(s):  
Wioleta Błaszczak-Bąk ◽  
Zoltan Koppanyi ◽  
Charles Toth
Keyword(s):  
Data Reduction ◽  
Point Cloud ◽  
Laser Scanning ◽  
Digital Terrain Model ◽  
New Approach ◽  
Terrain Model ◽  
Digital Terrain ◽  
Airborne Laser ◽  
Short Time ◽  
Mls Method

Mobile Laser Scanning (MLS) technology acquires a huge volume of data in a very short time. In many cases, it is reasonable to reduce the size of the dataset with eliminating points in such a way that the datasets, after reduction, meet specific optimization criteria. Various methods exist to decrease the size of point cloud, such as raw data reduction, Digital Terrain Model (DTM) generalization or generation of regular grid. These methods have been successfully applied on data captured from Airborne Laser Scanning (ALS) and Terrestrial Laser Scanning (TLS), however, they have not been fully analyzed on data captured by an MLS system. The paper presents our new approach, called the Optimum Single MLS Dataset method (OptD-single-MLS), which is an algorithm for MLS data reduction. The tests were carried out in two variants: (1) for raw sensory measurements and (2) for a georeferenced 3D point cloud. We found that the OptD-single-MLS method provides a good solution in both variants; therefore, the choice of the reduction variant depends only on the user.

Regional lung water and hematocrit determined by positron emission tomography

1985 ◽  
Vol 59 (3) ◽  
pp. 860-868 ◽  
Author(s):  
D. P. Schuster ◽  
M. A. Mintun ◽  
M. A. Green ◽  
M. M. Ter-Pogossian
Keyword(s):  
Positron Emission Tomography ◽  
Regional Distribution ◽  
Vertical Gradient ◽  
Emission Tomography ◽  
Lung Water ◽  
Average Value ◽  
Positron Emission ◽  
Significant Difference ◽  
Regional Basis ◽  
The Difference

We have measured with positron emission tomography (PET) the regional distribution of extravascular lung water (EVLW) and hematocrit (HctL) in normal supine dogs. H2(15)O and C15O were used as total lung water (TLW) and intravascular water (IVW) compartment labels, respectively. An additional plasma volume label (68Ga-transferrin) was used to determine regional HctL. EVLW was calculated as the difference between TLW and IVW. In 13 dogs, EVLW was relatively constant along a gravity-dependent vertical gradient, although values in the most anterior regions were statistically less (P less than 0.05) than those in more posterior ones. The average value for EVLW (13 dogs) was 14.4 +/- 2.5 ml H2O/100 ml lung. When EVLW was compared with IVW on a regional basis, the EVLW/IVW ratio decreased significantly in a gravity-dependent direction from 1.95 +/- 0.28 to 0.88 +/- 0.18. In 7 dogs, no significant difference between HctL and systemic hematocrit (average ratio 1.01 +/- 0.08) was found nor was any significant variation of HctL within the lung detected. Thus, in contrast to gravimetric techniques, a hematocrit correction does not appear to be necessary when regional EVLW is studied by PET.

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