High-resolution GRACE Monthly Gravity Field Solutions Expressed as Geopotential Coefficients

2021 ◽  
Author(s):  
Qiujie Chen ◽  
Jürgen Kusche ◽  
Yunzhong Shen ◽  
Xingfu Zhang
Keyword(s):  
High Resolution ◽  
Gravity Field ◽  
Spatial Resolution ◽  
Spherical Harmonic ◽  
Regularization Method ◽  
A Priori ◽  
Spatial Constraints ◽  
Spherical Harmonic Models ◽  
Priori Information ◽  
Geopotential Coefficients

<p>The commonly used filters (e.g. Gaussian smoothing, decorrelation and DDK filtering) applied to GRACE spherical harmonic gravity field solutions generally lead to reduced resolution, signal damping and leakage. This work is dedicated to improving spatial resolution and reducing signal damping by developing a regularization method with spectral constraints to spherical harmonics. Before constructing the spectral constraints, we create spatial constraints over global grids (covering lands, oceans and the boundaries between lands and oceans) from the a priori information of GRACE spherical harmonic models. Since we are solving geopotential coefficients rather than mascon grids, we further transfer the spatial constraints into the spectral domain according to the law of variance-covariance propagation, leading to spectral constraints regarding geopotential coefficients. In our work, the regularization method with spectral constraints was demonstrated to have comparable ability as mascon modelling method to enhance the spatial resolution and signal power besides reducing signal leakage. Applying the presented method with spatial constraints, we produced the first time series of high-resolution gravity field solutions expressed as geopotential coefficients complete to degree and order 180. Our analyses over the global and regional areas show that our high-resolution solutions are in good agreement with CSR and JPL mascon solutions.</p>

scholarly journals Seismic Constrained Gravity Inversion: A Reliable Tool to Improve Geophysical Models Away from Seismic Information

Geosciences ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 467
Author(s):  
Daniele Sampietro ◽  
Martina Capponi
Keyword(s):  
High Resolution ◽  
Gravity Field ◽  
A Priori ◽  
Geophysical Methods ◽  
Real Life ◽  
Gravity Inversion ◽  
Seismic Surveys ◽  
Real Model ◽  
Gravity Fields ◽  
Priori Information

The exploitation of gravity fields in order to retrieve information about subsurface geological structures is sometimes considered a second rank method, in favour of other geophysical methods, such as seismic, able to provide a high resolution detailed picture of the main geological horizons. Within the current work we prove, through a realistic synthetic case study, that the gravity field, thanks to the availability of freely of charge high resolution global models and to the improvements in the gravity inversion methods, can represent a valid and cheap tool to complete and enhance geophysical modelling of the Earth’s crust. Three tests were carried out: In the first one a simple two-layer problem was considered, while in tests two and three we considered two more realistic scenarios in which the availability on the study area of constraints derived from 3D or 2D seismic surveys were simulated. In all the considered test cases, in which we try to simulate real-life scenarios, the gravity field, inverted by means of an advanced Bayesian technique, was able to obtain a final solution closer to the (simulated) real model than the assumed a priori information, typically halving the uncertainties in the geometries of the main geological horizons with respect to the initial model.

scholarly journals Influence of low spatial resolution a priori data on tropospheric NO<sub>2</sub> satellite retrievals

2011 ◽  
Vol 4 (9) ◽  
pp. 1805-1820 ◽  
Author(s):  
A. Heckel ◽  
S.-W. Kim ◽  
G. J. Frost ◽  
A. Richter ◽  
M. Trainer ◽  
...  
Keyword(s):  
High Resolution ◽  
San Francisco ◽  
Spatial Resolution ◽  
Power Plants ◽  
Transport Model ◽  
A Priori ◽  
Satellite Observations ◽  
Chemical Transport Model ◽  
Under Sampling ◽  
Priori Information

Abstract. The retrieval of tropospheric columns of NO2 and other trace gases from satellite observations of backscattered solar radiation relies on the use of accurate a priori information. The spatial resolution of current space sensors is often significantly higher than that of the a priori datasets used, introducing uncertainties from spatial misrepresentation. In this study, the effect of spatial under-sampling of a priori data on the retrieval of NO2 columns was studied for a typical coastal area (around San Francisco). High-resolution (15 × 15 km2) NO2 a priori data from the WRF-Chem model in combination with high-resolution MODIS surface reflectance and aerosol data were used to investigate the uncertainty introduced by applying a priori data at typical global chemical transport model resolution. The results show that the relative uncertainties can be large (more than a factor of 2 if all a priori data used is at the coarsest resolution) for individual measurements, mainly due to spatial variations in NO2 profile and surface albedo, with smaller contributions from aerosols and surface height changes. Similar sensitivities are expected for other coastal regions and localised sources such as power plants, highlighting the need for high-resolution a priori data in quantitative analysis of the spatial patterns retrieved from satellite observations of tropospheric pollution.

scholarly journals A 3-D tomographic retrieval approach with advection compensation for the air-borne limb-imager GLORIA

2011 ◽  
Vol 4 (11) ◽  
pp. 2509-2529 ◽  
Author(s):  
J. Ungermann ◽  
J. Blank ◽  
J. Lotz ◽  
K. Leppkes ◽  
L. Hoffmann ◽  
...  
Keyword(s):  
Spatial Resolution ◽  
A Priori ◽  
Horizontal Resolution ◽  
Line Of Sight ◽  
Wind Fields ◽  
Closed Curves ◽  
Flight Direction ◽  
Mesoscale Structures ◽  
Priori Information ◽  
Horizontal View

Abstract. Infrared limb sounding from aircraft can provide 2-D curtains of multiple trace gas species. However, conventional limb sounders view perpendicular to the aircraft axis and are unable to resolve the observed airmass along their line-of-sight. GLORIA (Gimballed Limb Observer for Radiance Imaging of the Atmosphere) is a new remote sensing instrument that is able to adjust its horizontal view angle with respect to the aircraft flight direction from 45° to 135°. This will allow for tomographic measurements of mesoscale structures for a wide variety of atmospheric constituents. Many flights of the GLORIA instrument will not follow closed curves that allow measuring an airmass from all directions. Consequently, it is examined by means of simulations, what spatial resolution can be expected under ideal conditions from tomographic evaluation of measurements made during a straight flight. It is demonstrated that the achievable horizontal resolution in the line-of-sight direction could be reduced from over 200 km to around 70 km compared to conventional retrievals and that the tomographic retrieval is also more robust against horizontal gradients in retrieved quantities in this direction. In a second step, it is shown that the incorporation of channels exhibiting different optical depth can further enhance the spatial resolution of 3-D retrievals enabling the exploitation of spectral samples usually not used for limb sounding due to their opacity. A second problem for tomographic retrievals is that advection, which can be neglected for conventional retrievals, plays an important role for the time-scales involved in a tomographic measurement flight. This paper presents a method to diagnose the effect of a time-varying atmosphere on a 3-D retrieval and demonstrates an effective way to compensate for effects of advection by incorporating wind-fields from meteorological datasets as a priori information.

An optimal regularization method for convolution equations on the sourcewise represented set

2015 ◽  
Vol 23 (5) ◽  
Author(s):  
Ye Zhang ◽  
Dmitry V. Lukyanenko ◽  
Anatoly G. Yagola
Keyword(s):  
Integral Equation ◽  
Regularization Method ◽  
A Priori ◽  
Noisy Data ◽  
Optimal Recovery ◽  
Multidimensional Case ◽  
A Priori Information ◽  
Ill Posed ◽  
Priori Information ◽  
Convolution Equations

AbstractIn this article, we consider an inverse problem for the integral equation of the convolution type in a multidimensional case. This problem is severely ill-posed. To deal with this problem, using a priori information (sourcewise representation) based on optimal recovery theory we propose a new method. The regularization and optimization properties of this method are proved. An optimal minimal a priori error of the problem is found. Moreover, a so-called optimal regularized approximate solution and its corresponding error estimation are considered. Efficiency and applicability of this method are demonstrated in a numerical example of the image deblurring problem with noisy data.

Using Deconvolution to Improve PET Spatial Resolution in OSEM Iterative Reconstruction

2007 ◽  
Vol 46 (02) ◽  
pp. 231-235 ◽  
Author(s):  
I. Castiglioni ◽  
G. Russo ◽  
M. Tana ◽  
F. Dell'Acqua ◽  
M. Gilardi ◽  
...  
Keyword(s):  
Image Reconstruction ◽  
Spatial Resolution ◽  
Penalty Function ◽  
Iterative Reconstruction ◽  
A Priori ◽  
Image Deconvolution ◽  
A Priori Information ◽  
Novel Approach ◽  
Priori Information ◽  
Pet Image Reconstruction

Summary Objectives : A novel approach to the PET image reconstruction is presented, based on the inclusion of image deconvolution during conventional OSEM reconstruction. Deconvolution is here used to provide a recovered PET image to be included as “a priori" information to guide OSEM toward an improved solution. Methods : Deconvolution was implemented using the Lucy-Richardson (LR) algorithm: Two different deconvolution schemes were tested, modifying the conventional OSEM iterative formulation: 1) We built a regularizing penalty function on the recovered PET image obtained by deconvolution and included i in the OSEM iteration. 2) After each conventional global OSEM iteration, we deconvolved the resulting PET image and used this “recovered" version as the initialization image for the next OSEM iteration. Tests were performed on both simulated and acquired data. Results : Compared to the conventional OSEM, both these strategies, applied to simulated and acquired data, showed an improvement in image spatial resolution with better behavior in the second case. In this way, small lesions, present on data, could be better discriminated in terms of contrast. Conclusions : Application of this approach to both simulated and acquired data suggests its efficacy in obtaining PET images of enhanced quality.

Logistical and technical considerations for the use of unmanned aircraft systems in coastal habitat monitoring: A case study in high-resolution subaquatic vegetation assessment

Shore & Beach ◽  
2020 ◽  
pp. 46-52
Keyword(s):  
High Resolution ◽  
Spatial Resolution ◽  
A Priori ◽  
Unmanned Aircraft ◽  
Unmanned Aircraft Systems ◽  
Coastal Habitat ◽  
Lower Altitude ◽  
Seagrass Meadows ◽  
Aircraft Systems ◽  
Natural Resource Managers

In recent years, the technology and regulation surrounding the use of unmanned aircraft systems (UASs) has rapidly advanced. This has resulted in the availability of such technology for more common applications. Here we compare manned versus UAS platforms for acquiring high-resolution imagery of subaquatic habitat for the purpose of boat propeller scar delineation in seagrass meadows in Redfish Bay, Texas. We acquired aerial seagrass imagery in three 20-hectare plots using two UASs and one manned aircraft platform. The three plots represented a priori designations of low, moderate, and high seagrass scarring intensity. Overall, we observed that a smaller amount of scarring was detected in the manned aircraft imagery compared to that collected by the two UAS platforms, and that this disparity was much greater for the high scarring intensity plot. The observed differences in scar feature delineations were at least partially related to logistical difference between these two platforms — specifically, the lower altitude flown by the UASs results in a higher spatial resolution of the imagery that is less dependent on the camera specifications. From a logistical standpoint, the potential gain in spatial resolution via lower altitude flight could result in a reduced pricetag for high-resolution mapped products. Further, the rapid deployment and local operation typically resulting from the accessibility of UAS training greatly simplify the logistics of planning imagery acquisition at the appropriate scale. However, we realize that the current trade-off with regard to higher altitude is the ability to cover large areas with fewer transects and shorter flight time. Coverage limitations for UASs is currently rooted in both technological and legal issues. However, as technology and regulations evolve, the technical and logistical comparison of imagery products from UAS and manned platforms will become increasingly important to natural resource managers and researchers looking to make this transition to UAS.

scholarly journals Practical Tips for 3D Regional Gravity Inversion

Geosciences ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 351 ◽  
Author(s):  
Daniele Sampietro ◽  
Martina Capponi
Keyword(s):  
Spatial Resolution ◽  
Mass Density ◽  
A Priori ◽  
Regional Scale ◽  
Gravity Inversion ◽  
A Priori Information ◽  
Numerical Examples ◽  
Priori Information ◽  
Regional Gravity ◽  
The Ideal

To solve the inverse gravimetric problem, i.e., to estimate the mass density distribution that generates a certain gravitational field, at local or regional scale, several parameters have to be defined such as the dimension of the 3D region to be considered for the inversion, its spatial resolution, the size of its border, etc. Determining the ideal setting for these parameters is in general difficult: theoretical solutions are usually not possible, while empirical ones strongly depend on the specific target of the inversion and on the experience of the user performing the computation. The aim of the present work is to discuss empirical strategies to set these parameters in such a way to avoid distortions and errors within the inversion. In particular, the discussion is focused on the choice of the volume of the model to be inverted, the size of its boundary, its spatial resolution, and the spatial resolution of the a-priori information to be used within the data reduction. The magnitude of the possible effects due to a wrong choice of the above parameters is also discussed by means of numerical examples.

scholarly journals Применение плоских импульсных акустических волн в устройствах с фазированными решетками для ультразвуковой визуализации в слоистых средах

2018 ◽  
Vol 44 (16) ◽  
pp. 41
Author(s):  
С.А. Титов
Keyword(s):  
Wave Propagation ◽  
Detailed Analysis ◽  
Spatial Resolution ◽  
A Priori ◽  
A Priori Information ◽  
Acoustical Parameters ◽  
Theoretical Limit ◽  
Intermediate Layers ◽  
Priori Information ◽  
Ultrasonic Images

AbstractA new method of constructing ultrasonic images in layered media is proposed that is based on the radiation and reception of plane pulsed waves at various angles. Upon passage via a set of layers, plane pulsed waves do not change their shape and direction in the imaged region, which eliminates the need for detailed analysis of wave propagation in intermediate layers. It is shown that, in the absence of a priori information on the thicknesses and acoustical parameters of layers or the results of their measurement, the proposed method allows images to be obtained at a spatial resolution corresponding to the theoretical limit.

Digital Image Processing in High Resolution Electron Microscopy

1975 ◽  
Vol 33 ◽  
pp. 12-13
Author(s):  
J. Frank
Keyword(s):  
Image Processing ◽  
High Resolution ◽  
Signal To Noise Ratio ◽  
A Priori ◽  
Image Interpretation ◽  
High Resolution Electron Microscopy ◽  
Input Image ◽  
Additional Information ◽  
Resolution Electron ◽  
Priori Information

Image processing can be considered as an attempt to aid image interpretation and to improve image quality by using additional information not contained in the image, or to make optimal use of redundant information contained in the image. Since high resolution electron micrographs contain a very high amount of noise from substrate, electron statistics and photographic grain, the separation of the signal from the noise part of the image is one of the most important problems. An operation that produces an output image with a higher signal-to-noise ratio than the input image may appear as witchcraft but is in fact feasible through clever use of a-priori information such as the knowledge of object and noise statistics.

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