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.

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.

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).

scholarly journals Continuous record of the gravity changes at Mt. Vesuvius

1997 ◽  
Vol 40 (5) ◽  
Author(s):  
G. Berrino ◽  
G Corrado ◽  
R. Magliulo ◽  
U. Riccardi
Keyword(s):  
Southern Italy ◽  
Absolute Gravity ◽  
Time Interval ◽  
Data Set ◽  
Gravity Station ◽  
Hourly Data ◽  
Continuous Record ◽  
Gravity Measurements ◽  
Time Variations ◽  
Comparison Of The Results

High precision relative and absolute gravity measurements are periodically carried out at Mt. Vesuvius (Southern Italy) to monitor the changes in the gravity field caused by the internal dynamics of the volcano. Moreover, a recording gravity station is also operating at the Osservatorio Vesuviano (Old Building) aimed at measuring in continuous mode the time variations of the gravity and the tidal parameters, possibly due to changes in the physical state of the volcano. The analysis carried out on an hourly data set spanning the 1994-1996 time interval and a comparison of the results with those previously obtained, exhibit a change in the tidal parameters which occurred between 1991 and 1994. A gravity decrease of about 60 µGal was observed during the same time interval in the same area. Consistent with relative and absolute gravity observations, no significant variations have been detected since 1994 in the tidal parameters and gravity residuals.

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.

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.

The Determinants of Capital Adequacy Ratio: The Case of the Vietnamese Banking System in the Period 2011-2015

2017 ◽  
Vol 33 (2) ◽  
Author(s):  
Ngoc Anh Nguyen
Keyword(s):  
Banking System ◽  
Precious Metals ◽  
Capital Adequacy ◽  
The Other ◽  
Total Asset ◽  
Data Set ◽  
Hand Size ◽  
Net Interest Margin ◽  
Capital Adequacy Ratio ◽  
Positive Effect

The analysis of a data set of observation for Vietnamese banks in period from 2011 - 2015 shows how Capital Adequacy Ratio (CAR) is influenced by selected factors: asset of the bank SIZE, loans in total asset LOA, leverage LEV, net interest margin NIM, loans lost reserve LLR, Cash and Precious Metals in total asset LIQ. Results indicate based on data that NIM, LIQ have significant effect on CAR. On the other hand, SIZE and LEV do not appear to have significant effect on CAR. Variables NIM, LIQ have positive effect on CAR, while variables LLR and LOA are negatively related with CAR.

scholarly journals Measurement of the D → K−π+π+π− and D → K−π+π0 coherence factors and average strong-phase differences in quantum-correlated $$ D\overline{D} $$ decays

2021 ◽  
Vol 2021 (5) ◽  
Author(s):  
M. Ablikim ◽  
◽  
M. N. Achasov ◽  
P. Adlarson ◽  
S. Ahmed ◽  
...  
Keyword(s):  
The Other ◽  
Unitarity Triangle ◽  
Quantum Superposition ◽  
Final State ◽  
Data Set ◽  
Strong Phase ◽  
Signal Decay ◽  
Belle Ii ◽  
Coherence Factors ◽  
Phase Differences

Abstract The decays D → K−π+π+π− and D → K−π+π0 are studied in a sample of quantum-correlated $$ D\overline{D} $$ D D ¯ pairs produced through the process e+e− → ψ(3770) → $$ D\overline{D} $$ D D ¯ , exploiting a data set collected by the BESIII experiment that corresponds to an integrated luminosity of 2.93 fb−1. Here D indicates a quantum superposition of a D0 and a $$ {\overline{D}}^0 $$ D ¯ 0 meson. By reconstructing one neutral charm meson in a signal decay, and the other in the same or a different final state, observables are measured that contain information on the coherence factors and average strong-phase differences of each of the signal modes. These parameters are critical inputs in the measurement of the angle γ of the Unitarity Triangle in B− → DK− decays at the LHCb and Belle II experiments. The coherence factors are determined to be RK3π = $$ {0.52}_{-0.10}^{+0.12} $$ 0.52 − 0.10 + 0.12 and $$ {R}_{K{\pi \pi}^0} $$ R K ππ 0 = 0.78 ± 0.04, with values for the average strong-phase differences that are $$ {\delta}_D^{K3\pi }=\left({167}_{-19}^{+31}\right){}^{\circ} $$ δ D K 3 π = 167 − 19 + 31 ° and $$ {\delta}_D^{K{\pi \pi}^0}=\left({196}_{-15}^{+14}\right){}^{\circ} $$ δ D K ππ 0 = 196 − 15 + 14 ° , where the uncertainties include both statistical and systematic contributions. The analysis is re-performed in four bins of the phase-space of the D → K−π+π+π− to yield results that will allow for a more sensitive measurement of γ with this mode, to which the BESIII inputs will contribute an uncertainty of around 6°.

scholarly journals BATCH PROCESSING OF TREE-RING SAMPLES FOR RADIOCARBON ANALYSIS

Radiocarbon ◽  
2020 ◽  
pp. 1-13
Author(s):  
Alexandra Fogtmann-Schulz ◽  
Sabrina G K Kudsk ◽  
Florian Adolphi ◽  
Christoffer Karoff ◽  
Mads F Knudsen ◽  
...  
Keyword(s):  
High Precision ◽  
Tree Rings ◽  
Precision Measurement ◽  
Radiocarbon Dating ◽  
The Other ◽  
High Precision Measurement ◽  
Machine Performance ◽  
High Throughput Method ◽  
Ca 50 ◽  
Low Activity

ABSTRACT We here present a comparison of methods for the pretreatment of a batch of tree rings for high-precision measurement of radiocarbon at the Aarhus AMS Centre (AARAMS), Aarhus University, Denmark. The aim was to develop an efficient and high-throughput method able to pretreat ca. 50 samples at a time. We tested two methods for extracting α-cellulose from wood to find the most optimal for our use. One method used acetic acid, the other used HCl acid for the delignification. The testing was conducted on background 14C samples, in order to assess the effect of the different pretreatment methods on low-activity samples. Furthermore, the extracted wood and cellulose fractions were analyzed using Fourier transform infrared (FTIR) spectroscopy, which showed a successful extraction of α-cellulose from the samples. Cellulose samples were pretreated at AARAMS, and the graphitization and radiocarbon analysis of these samples were done at both AARAMS and the radiocarbon dating laboratory at Lund University to compare the graphitization and AMS machine performance. No significant offset was found between the two sets of measurements. Based on these tests, the pretreatment of tree rings for high-precision radiocarbon analysis at AARAMS will henceforth use HCI for the delignification.

scholarly journals Evaluating Presence/Absence of Target Microbes in Microbiological Tests

2000 ◽  
Vol 83 (6) ◽  
pp. 1429-1434
Author(s):  
Robert J Blodgett ◽  
Anthony D Hitchins
Keyword(s):  
Performance Studies ◽  
Collaborative Study ◽  
False Negative ◽  
The Other ◽  
Test Results ◽  
Logistic Curve ◽  
Microbiological Method ◽  
Test Portion ◽  
Method Performance ◽  
Data Set

Abstract A typical qualitative microbiological method performance (collaborative) study gathers a data set of responses about a test for the presence or absence of a target microbe. We developed 2 models that estimate false-positive and false-negative rates. One model assumes a constant probability that the tests will indicate the target microbe is present for any positive concentration in the test portion. The other model assumes that this probability follows a logistic curve. Test results from several method performance studies illustrate these estimates.

Sign in / Sign up

Export Citation Format

Share Document