Regression technique to remove temporal variation from geomagnetic survey data

Geophysics ◽  
1982 ◽  
Vol 47 (10) ◽  
pp. 1437-1443 ◽  
Author(s):  
Eric L. Sander ◽  
Charmaine P. Mrazek
Keyword(s):  
Temporal Variation ◽  
Survey Data ◽  
Field Measurements ◽  
Open Ocean ◽  
Regression Technique ◽  
Geomagnetic Survey ◽  
Regression Techniques

A flexible and effective set of procedures has been developed to reconstruct the temporal variation occurring during a geomagnetic survey. These procedures use regression techniques and the field measurements made at survey track intersections. They have been applied to both ship and aircraft survey data collected in open ocean areas to remove from 60 to 80 percent of the temporal variation. This paper presents these procedures and the results for one ship and one aircraft survey.

scholarly journals Global Observations of Open-Ocean Mode-1 M2 Internal Tides

2016 ◽  
Vol 46 (6) ◽  
pp. 1657-1684 ◽  
Author(s):  
Zhongxiang Zhao ◽  
Matthew H. Alford ◽  
James B. Girton ◽  
Luc Rainville ◽  
Harper L. Simmons
Keyword(s):  
Energy Loss ◽  
Internal Tide ◽  
Field Measurements ◽  
Open Ocean ◽  
Internal Tides ◽  
Global Integration ◽  
Tidal Waves ◽  
Topographic Features ◽  
Midocean Ridges ◽  
The Pacific

AbstractA global map of open-ocean mode-1 M2 internal tides is constructed using sea surface height (SSH) measurements from multiple satellite altimeters during 1992–2012, representing a 20-yr coherent internal tide field. A two-dimensional plane wave fit method is employed to 1) suppress mesoscale contamination by extracting internal tides with both spatial and temporal coherence and 2) separately resolve multiple internal tidal waves. Global maps of amplitude, phase, energy, and flux of mode-1 M2 internal tides are presented. The M2 internal tides are mainly generated over topographic features, including continental slopes, midocean ridges, and seamounts. Internal tidal beams of 100–300 km width are observed to propagate hundreds to thousands of kilometers. Multiwave interference of some degree is widespread because of the M2 internal tide’s numerous generation sites and long-range propagation. The M2 internal tide propagates across the critical latitudes for parametric subharmonic instability (28.8°S/N) with little energy loss, consistent with the 2006 Internal Waves across the Pacific (IWAP) field measurements. In the eastern Pacific Ocean, the M2 internal tide loses significant energy in propagating across the equator; in contrast, little energy loss is observed in the equatorial zones of the Atlantic, Indian, and western Pacific Oceans. Global integration of the satellite observations yields a total energy of 36 PJ (1 PJ = 1015 J) for all the coherent mode-1 M2 internal tides. Finally, satellite observed M2 internal tides compare favorably with field mooring measurements and a global eddy-resolving numerical model.

Parametric Wave Spectrum Model for Typhoon-Generated Waves Based on Field Measurements in Nearshore Strait Water

2021 ◽  
Vol 143 (5) ◽  
Author(s):  
Kai Wei ◽  
Hasan Imani ◽  
Shunquan Qin
Keyword(s):  
Temporal Variation ◽  
East Coast ◽  
Wave Spectrum ◽  
Field Measurements ◽  
Offshore Structures ◽  
Critical Parameters ◽  
Wave Spectra ◽  
Wave Data ◽  
Stochastic Waves ◽  
Spectrum Model

Abstract The stochastic waves generated by storm landfalls usually determine the design and safety of coastal and offshore structures in typhoon regions. This study developed a parametric wave spectrum model for typhoon-generated stochastic waves that considers the variation in the wave spectrum due to the temporal variation in the typhoon. A field measurement campaign was conducted in nearshore strait water on the east coast of China to measure the wave data for two landfall typhoons: Soudelor and Dujuan. The measured wave data were filtered through a preprocessing framework. The parametric wave spectrum model was then developed based on the measured wave spectra for different stages of the typhoon. The main conclusions include the following: (1) 78% of the measured wave spectra at the example site under a typhoon are double-peaked, and approximately 15% are single-peaked; (2) the parametric model with either the Joint North Sea Wave Project (JONSWAP) or Ochi-Hubble (OH) kernel function is effective in defining the typhoon-generated wave spectra; and (3) the critical parameters of the developed model for typhoon-generated waves are site-specific and depend on the temporal variation of the typhoon.

scholarly journals Spatial and temporal variation in pH, alkalinity and conductivity in surface runoff and groundwater for the Upper River Severn catchment

1997 ◽  
Vol 1 (3) ◽  
pp. 697-715 ◽  
Author(s):  
T. Hill ◽  
C. Neal
Keyword(s):  
Temporal Variation ◽  
Ground Water ◽  
Field Measurements ◽  
Temporal Variations ◽  
Spatial And Temporal Variation ◽  
Flow Conditions ◽  
Land Usage ◽  
Load Analysis ◽  
Stream Waters ◽  
Upland Catchments

Abstract. Measurements of pH, alkalinity and electrical conductivity are used to examine the extent of the spatial and temporal variation in stream and ground water chemistry for the Upper Severn catchment, Plynlimon. Wide temporal variations in stream waters broadly reflect flow conditions and complex soil and ground water interactions but not soil type, land usage or geology. The results have major implications for the use of critical load analysis and the development and application of models in upland catchments. They point to the value of field measurements for assessing the environmental management of upland catchments, rather than the present use of over simplistic or inappropriate models.

TIME SERIES ANALYSIS IN AGROMETEOROLOGICAL PROBLEMS WITH EMPHASIS ON SPECTRUM ANALYSIS

1967 ◽  
Vol 47 (5) ◽  
pp. 477-491
Author(s):  
R. L. Desjardins
Keyword(s):  
Time Series ◽  
Environmental Factors ◽  
Time Series Analysis ◽  
Multiple Regression ◽  
Spectrum Analysis ◽  
Meteorological Parameters ◽  
Regression Technique ◽  
Cross Spectrum ◽  
Time Series Studies ◽  
Regression Techniques

This paper reviews the principles and use of spectrum analysis and discusses the effectiveness of combining multiple regression techniques with cross-spectrum analysis in time series studies. This method is useful in comparing the variations of an empirical index or the response of different instruments to environmental factors as a function of time. The variability of daily latent-evaporation estimates from a regression technique is examined and compared with evaporation readings from atmometers. A comparison is made of the variation in evaporation from two types of small atmometers and two types of tank evaporimeters. All four instruments appear to respond to meteorological parameters similarly at Swift Current and Ottawa.

scholarly journals Improved Direction-of-Arrival Estimation of an Acoustic Source Using Support Vector Regression and Signal Correlation

Sensors ◽  
2021 ◽  
Vol 21 (8) ◽  
pp. 2692
Author(s):  
Faisal Alam ◽  
Mohammed Usman ◽  
Hend I. Alkhammash ◽  
Mohd Wajid
Keyword(s):  
Support Vector Regression ◽  
Cross Correlation ◽  
Direction Of Arrival ◽  
Doa Estimation ◽  
Regression Technique ◽  
Support Vector ◽  
Correlation Technique ◽  
Multilevel Regression ◽  
Acoustic Source ◽  
Regression Techniques

The direction-of-arrival (DoA) estimation of an acoustic source can be estimated with a uniform linear array using classical techniques such as generalized cross-correlation, beamforming, subspace techniques, etc. However, these methods require a search in the angular space and also have a higher angular error at the end-fire. In this paper, we propose the use of regression techniques to improve the results of DoA estimation at all angles including the end-fire. The proposed methodology employs curve-fitting on the received multi-channel microphone signals, which when applied in tandem with support vector regression (SVR) provides a better estimation of DoA as compared to the conventional techniques and other polynomial regression techniques. A multilevel regression technique is also proposed, which further improves the estimation accuracy at the end-fire. This multilevel regression technique employs the use of linear regression over the results obtained from SVR. The techniques employed here yielded an overall 63% improvement over the classical generalized cross-correlation technique.

scholarly journals A Review on Different Regression Techniques and its applications used in Machine Learning

2021 ◽  
Vol 3 (2) ◽  
pp. 217-220
Author(s):  
Anmol Kaur ◽  
Jaspreet Kaur ◽  
Maninder Kaur
Keyword(s):  
Biological Sciences ◽  
Machine Learning ◽  
Regression Analysis ◽  
Social Studies ◽  
Numerical Investigation ◽  
Research Paper ◽  
Regression Technique ◽  
Almost Everywhere ◽  
Regression Techniques

Regression Analysis is an assortment of factual methods that fill in as an explanation behind drawing acceptances about associations among the various interrelated elements. This technique is pretty much applicable in almost everywhere in study field which includes biological sciences, social studies and relapse examination. The main purpose of this research paper is to evolve the vital hypothesis for the factual Regression Technique and also to demonstrate the hypothesis with a collection of wide variety of various models looked over economical aspects, demography, sketching and engineering concepts. To assemble the relevant content which is independent from various insights, mathematics based on variable and numerical investigation is included.

Calculating macroalgal height and biomass using bathymetric LiDAR and a comparison with surface area derived from satellite data in Nova Scotia, Canada

2020 ◽  
Vol 63 (1) ◽  
pp. 43-59 ◽  
Author(s):  
Tim Webster ◽  
Candace MacDonald ◽  
Kevin McGuigan ◽  
Nathan Crowell ◽  
Jean-Sebastien Lauzon-Guay ◽  
...  
Keyword(s):  
Nova Scotia ◽  
Surface Area ◽  
Survey Data ◽  
Satellite Data ◽  
High Tide ◽  
Field Measurements ◽  
Ground Truth ◽  
Cost Effective ◽  
Satellite System ◽  
Ground Truth Data

AbstractThe ability to map and monitor the macroalgal coastal resource is important to both the industry and the regulator. This study evaluates topo-bathymetric lidar (light detection and ranging) as a tool for estimating the surface area, height and biomass of Ascophyllum nodosum, an anchored and vertically suspended (floating) macroalga, and compares the surface area derived from lidar and WorldView-2 satellite imagery. Pixel-based Maximum Likelihood classification of low tide satellite data produced 2-dimensional maps of intertidal macroalgae with overall accuracy greater than 80%. Low tide and high tide topo-bathymetric lidar surveys were completed in southwestern Nova Scotia, Canada. Comparison of lidar-derived seabed elevations with ground-truth data collected using a survey grade global navigation satellite system (GNSS) indicated the low tide survey data have a positive bias of 15 cm, likely resulting from the seaweed being draped over the surface. The high tide survey data did not exhibit this bias, although the suspended canopy floating on the water surface reduced the seabed lidar point density. Validation of lidar-derived seaweed heights indicated a mean difference of 30 cm with a root mean square error of 62 cm. The modelled surface area of seaweed was 28% greater in the lidar model than the satellite model. The average lidar-derived biomass estimate was within one standard deviation of the mean biomass measured in the field. The lidar method tends to overestimate the biomass compared to field measurements that were spatially biased to the mid-intertidal level. This study demonstrates an innovative and cost-effective approach that uses a single high tide bathymetric lidar survey to map the height and biomass of dense macroalgae.

Methods of analysing competition with special reference to herbage plants: II. Effects of associate plants

1973 ◽  
Vol 81 (1) ◽  
pp. 91-98 ◽  
Author(s):  
J. Hill
Keyword(s):  
Special Reference ◽  
Present Experiment ◽  
Theoretical Models ◽  
Regression Technique ◽  
Frequency Dependent ◽  
Density Dependent ◽  
Regression Techniques ◽  
Dependent Density

SummaryAn examination of the role played by associate plants in conditioning the behaviour of a competitor was carried out on a diallel arrangement of five perennial ryegrasa genotypes using regression techniques similar to those devised for the analysis of genotype-environment interactions. By far the largest proportion of the significant genotype x associate interaction could be ascribed to differences between the slopes of the fitted regression lines, with the three long-leaved genotypes (A, C and E)having the highest slopes and hence being the most sensitive to changes in the associate environment. Significant departures from the fitted regression lines occurred, however, but these could be traced solely to genotype C.Theoretical models capable of identifying those conditions under which 50:50 mixtures may be expected, first, to exceed the average of their component monocultures, and secondly, to surpass the better monoculture, were developed. Applying these models to the present experiment confirms that the performance of the 50:50 mixtures generally exceeds the monoculture average, but rarely surpasses the better monoculture.The scope of the regression technique was broadened to incorporate the 75:25 and 25: 75 mixtures, thereby revealing that the response of the two strongest competitors (C and E) is frequency dependent. Density dependent effects were also uncovered in this material, with genotype C the strongest competitor, being particularly noteworthy in this respect. The role of this regression technique in the development of new and highly productive mixtures is briefly discussed.

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