scholarly journals Testing of the 4SM Method in the Gulf of California Suggests Field Data Are not Needed to Derive Satellite Bathymetry

Sensors ◽  
2017 ◽  
Vol 17 (10) ◽  
pp. 2248 ◽  
Author(s):  
Fabio Favoretto ◽  
Yann Morel ◽  
Andrew Waddington ◽  
Jorge Lopez-Calderon ◽  
Marco Cadena-Roa ◽  
...  
Keyword(s):  
Gulf Of California ◽  
Field Data ◽  
Satellite Bathymetry

scholarly journals 4SM Method Tested in the Gulf of California Suggests Field Data are Not Needed to Derive Satellite Bathymetry

2017 ◽  
Author(s):  
Fabio Favoretto ◽  
Yann Morel ◽  
Andrew Waddington ◽  
Jorge Lopez-Calderon ◽  
Marco Cadena-Roa ◽  
...  
Keyword(s):  
Time Series ◽  
Gulf Of California ◽  
Field Data ◽  
Control Method ◽  
Spectral Characteristics ◽  
Landsat 8 ◽  
Multispectral Images ◽  
Band Ratio ◽  
Average Accuracy ◽  
Satellite Bathymetry

Satellite derived bathymetry methods over coastal areas were born to deliver basic and useful information like bathymetry. However, the process is not straightforward, the main limitation being the need of field data. The Self-calibrated Spectral Supervised Shallow-water Modeler (4SM) method was tested to obtain coastal bathymetry without the use of any field data. Using LANDSAT-8 multispectral images from 2013 to 2016, a bathymetric time series was produced. Groundtruthed depths and an alternative method, Stumpf’s Band Ratio Algorithm, were used to verify the results. Retrieved (4SM) vs groundtruthed depths scored an average r2 (0.90), and a low error (RMSE = 1.47 m). Also 4SM showed, over the whole time series, the same average accuracy of the control method (40%). Advantages, limitations and operability under complex atmosphere and water column conditions, and high and low-albedo bottom processing capabilities of 4SM are discussed. In conclusion, the findings suggest that 4SM is equally accurate as the commonly used Stumpf’s method, the only difference being the independence of 4SM to previous field data, and the potential to deliver bottom spectral characteristics for further modelling. 4SM represents a significative advance in coastal remote sensing potential to obtain bathymetry and optical properties of the marine bottom.

scholarly journals A Hybrid Bio-Optical Transformation for Satellite Bathymetry Modeling Using Sentinel-2 Imagery

2019 ◽  
Vol 11 (23) ◽  
pp. 2746 ◽  
Author(s):  
Athanasios K. Mavraeidopoulos ◽  
Emmanouil Oikonomou ◽  
Athanasios Palikaris ◽  
Serafeim Poulos
Keyword(s):  
Optical Properties ◽  
Field Data ◽  
Sea Water ◽  
Aegean Sea ◽  
Multispectral Images ◽  
Inherent Optical Properties ◽  
Sentinel 2A ◽  
Satellite Bathymetry ◽  
Optical Transformation ◽  
Sentinel 2

The article presents a new hybrid bio-optical transformation (HBT) method for the rapid modelling of bathymetry in coastal areas. The proposed approach exploits free-of-charge multispectral images and their processing by applying limited manpower and resources. The testbed area is a strait between two Greek Islands in the Aegean Sea with many small islets and complex seabed relief. The HBT methodology implements semi-analytical and empirical steps to model sea-water inherent optical properties (IOPs) and apparent optical properties (AOPs) observed by the Sentinel-2A multispectral satellite. The relationships of the calculated IOPs and AOPs are investigated and utilized to classify the study area into sub-regions with similar water optical characteristics, where no environmental observations have previously been collected. The bathymetry model is configured using very few field data (training depths) chosen from existing official nautical charts. The assessment of the HBT indicates the potential for obtaining satellite derived bathymetry with a satisfactory accuracy for depths down to 30 m.

scholarly journals Two-dimensional determinant inversion of marine magnetotelluric data and a field example from the Gulf of California, Mexico

Geophysics ◽  
2021 ◽  
Vol 86 (1) ◽  
pp. E37-E57
Author(s):  
Shunguo Wang ◽  
Steven Constable ◽  
Valeria Reyes-Ortega ◽  
Hormoz Jahandari ◽  
Colin Farquharson ◽  
...  
Keyword(s):  
Gulf Of California ◽  
Subduction Zones ◽  
Field Data ◽  
Real Data ◽  
Transverse Magnetic ◽  
Two Dimensional ◽  
Magnetotelluric Data ◽  
Earth Structures ◽  
3D Effects ◽  
2D Data

Two-dimensional marine magnetotelluric (MT) observations are useful for offshore geologic studies, such as natural resource exploration, fault mapping, fluid estimation at subduction zones, and the delineation of the lithosphere-asthenosphere boundary beneath the seafloor. Earth structures are often assumed to be two dimensional, which allows MT data to be decomposed into a transverse electric (TE) mode and a transverse magnetic (TM) mode. The 2D assumption can effectively reduce acquisition and computational costs. However, offline 3D effects and other problems such as lack/failure of the compass on instruments are often encountered, making it difficult to decompose data into the TE and TM modes. In these cases, 2D inversion may be misleading or may not provide an acceptable misfit to the marine MT observations. Thus, we have developed a 2D determinant inversion to the marine MT method to mitigate these difficulties, implemented in the MARE2DEM code, and we tested its utility using synthetic examples and a field example. In the synthetic examples, the determinant inversion demonstrates an ability to overcome 3D effects caused by 3D anomalies and bathymetry. With confidence from the synthetic tests, we interpreted real data acquired in the Gulf of California, Mexico, where not only is the bathymetry 3D in nature, but the external compasses failed to record the orientation. The field data can not only be fit to a reasonable misfit with a determinant inversion, but the resolved conductive zones also have a good correlation with known faults. A comparison between the resistivity model from the field data and a seismic reflection section shows that a previously interpreted fault, the Wagner Fault, should be shifted 5 km toward the southwest and made slightly steeper. Thus, the implementation of the determinant inversion may provide a new approach for using problematic 2D data.

Invariant TE and TM impedances in the marine magnetotelluric method

2020 ◽  
Vol 221 (1) ◽  
pp. 163-177 ◽  
Author(s):  
A M Montiel-Álvarez ◽  
J M Romo ◽  
S Constable ◽  
E Gómez-Treviño
Keyword(s):  
Gulf Of California ◽  
Field Data ◽  
Real Data ◽  
Quadratic Equation ◽  
Impedance Tensor ◽  
Usual Practice ◽  
Average Maximum ◽  
Magnetotelluric Method ◽  
Traditional Approaches ◽  
Rotational Invariants

SUMMARY The magnetotelluric (MT) impedance tensor has a nil diagonal when one of the axes of the coordinate system coincides with the strike of a 2-D structure. In general, real data are full tensors either because of 3-D effects or measurements not aligned to the geological strike. The usual practice to adapt the field tensor to the 2-D assumption is to rotate to a new system of coordinates. In most cases, there is no single angle of rotation that warranties that the diagonal elements become zeros as in the ideal 2-D case. Even maximizing the off-diagonal elements does not necessarily produce a nil diagonal. Consequently, the 2-D inversions proceed by neglecting whatever there is left in the diagonals. In this work, we explore an alternative that places no constraints on direction but assures a nil diagonal. We use two rotational invariants that compact the four elements of the tensor into only two and reduce in 2-D to the TE and TM impedances. These are obtained readily by solving a quadratic equation. We explore four different scenarios: (1) using the invariants, (2) rotating the tensor perpendicular to the profile, (3) rotating to the average maximum orientation for each station and (4) maximizing the off-diagonal elements of the tensor for each site, frequency to frequency. These approaches were applied to 3-D synthetic and field data. The field data correspond to two marine magnetotelluric surveys in the Gulf of California. In one of them, there is no information on the instrument orientation because the compasses failed. In this case, the rotational invariants come handy to overcome the problem. In the other survey, there was orientation information and the 2-D inversions illustrate the better performance of the invariants relative to the traditional approaches.

Boussinesq Wave Model Compared with Field Data

2001 ◽  
Author(s):  
Denis Morichon ◽  
Barbara Boczar-Karakiewicz ◽  
Edward B. Thornton
Keyword(s):  
Field Data ◽  
Wave Model

Mekanisme Dan Proteksi Jaminan Nasabah Pada Gadai Informal

Liquidity ◽  
2017 ◽  
Vol 6 (2) ◽  
pp. 103-109
Author(s):  
Yuri Nanda Larasati ◽  
Jafril Khalil
Keyword(s):  
Qualitative Research ◽  
Research Methods ◽  
Financial Services ◽  
Field Data ◽  
Qualitative Research Methods ◽  
Research Field ◽  
Consumer Society ◽  
Library Research ◽  
The Cost

Regulation of the financial services authority (OJK) No. 31/POJK.05/2016 on Venture had arranged that the financial services agency on the basis of the law of pledge is in coaching and supervision OJK. Yet the existence of laws – invitation to Governing Enterprise pawn shops causing business activities conducted by the above parties are not yet regulated. The condition is feared could cause harm to the consumer society. The purpose of this research is to know the procedures, mechanisms, protection of goods and guarantee the consumer on an informal pledge financing, methods of determination of the cost of maintenance of the goods and the goods of the execution mechanism of the pledge as well as protection for the collateral items are viewed from the side of the consumer by looking at laws-invitations and Sharia. To find out whether the pledge have gotten permission from OJK. This research uses qualitative research methods with the study of library research, field data and simulations. The approach used in this study is the empirical juridical approach. Elaboration upon the results is discussed further in this article.

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