Calibration correction of arbitrary optical distortions by non-parametric 3D disparity field for planar and volumetric PIV/LPT

In this study, a new image calibration approach is presented that corrects arbitrary optical distortions by utilizing non-parametric, 3D disparity fields. A calibration plate with a high spatial resolution (i.e., high density of calibration marks) was used to identify optical distortions that remain after the initial calibration, which were then used to create a correction field for the pinhole or polynomial mapping functions. Results from a pipe flow experiment with four cameras using volume self-calibration (VSC) and Shake-the-Box Lagrangian particle tracking (STB LPT) are presented and the impact of the improved calibration is discussed. Using the calibration marks with the correction field, distortions of initially more than 20 pixels are reduced below 1 pixel. Using VSC with the correction field allows further reduction of average calibration disparities below 0.02 pixels (maximum 0.5 pixels), whereas without a correction field the remaining average disparity is much higher at 1 pixel (maximum 5 pixels). STB analysis of the data shows a considerable higher spatial resolution at the pipe wall and a consistent spatial distribution of the number of detected particles in the measurement volume.

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Air quality impacts of COVID-19 lockdown measures detected from space using high spatial resolution observations of multiple trace gases from Sentinel-5P/TROPOMI

10.5194/acp-2021-534 ◽

2021 ◽

Author(s):

Pieternel F. Levelt ◽

Deborah C. Stein Zweers ◽

Ilse Aben ◽

Maite Bauwens ◽

Tobias Borsdorff ◽

...

Keyword(s):

Air Quality ◽

Spatial Resolution ◽

High Spatial Resolution ◽

Trace Gases ◽

Trace Gas ◽

Joint Analysis ◽

Anthropogenic Emissions ◽

China And India ◽

Societal Relevance ◽

The Impact

Abstract. The aim of this paper is two-fold: to provide guidance on how to best interpret TROPOMI trace gas retrievals and to highlight how TROPOMI trace gas data can be used to understand event-based impacts on air quality from regional to city-scales around the globe. For this study, we present the observed changes in the atmospheric column amounts of five trace gases (NO2, SO2, CO, HCHO and CHOCHO) detected by the Sentinel-5P TROPOMI instrument, driven by reductions of anthropogenic emissions due to COVID-19 lockdown measures in 2020. We report clear COVID-19-related decreases in NO2 concentrations on all continents. For megacities, reductions in column amounts of tropospheric NO2 range between 14 % and 63 %. For China and India supported by NO2 observations, where the primary source of anthropogenic SO2 is coal-fired power generation, we were able to detect sector-specific emission changes using the SO2 data. For HCHO and CHOCHO, we consistently observe anthropogenic changes in two-week averaged column amounts over China and India during the early phases of the lockdown periods. That these variations over such a short time scale are detectable from space, is due to the high resolution and improved sensitivity of the TROPOMI instrument. For CO, we observe a small reduction over China which is in concert with the other trace gas reductions observed during lockdown, however large, interannual differences prevent firm conclusions from being drawn. The joint analysis of COVID-19 lockdown-driven reductions in satellite observed trace gas column amounts, using the latest operational and scientific retrieval techniques for five species concomitantly is unprecedented. However, the meteorologically and seasonally driven variability of the five trace gases does not allow for drawing fully quantitative conclusions on the reduction of anthropogenic emissions based on TROPOMI observations alone. We anticipate that in future, the combined use of inverse modelling techniques with the high spatial resolution data from S5P/TROPOMI for all observed trace gases presented here, will yield a significantly improved sector-specific, space-based analysis of the impact of COVID-19 lockdown measures as compared to other existing satellite observations. Such analyses will further enhance the scientific impact and societal relevance of the TROPOMI mission.

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Interpreting high spatial resolution line observations of planet-forming disks with gaps and rings: the case of HD 163296

Astronomy and Astrophysics ◽

10.1051/0004-6361/202038712 ◽

2020 ◽

Vol 642 ◽

pp. A165

Author(s):

Ch. Rab ◽

I. Kamp ◽

C. Dominik ◽

C. Ginski ◽

G. A. Muro-Arena ◽

...

Keyword(s):

Spatial Resolution ◽

High Spatial Resolution ◽

Line Emission ◽

High Angular Resolution ◽

Back Side ◽

Gas Temperature ◽

Disk Model ◽

Gas Density ◽

The Impact ◽

Gas Properties

Context. Spatially resolved continuum observations of planet-forming disks show prominent ring and gap structures in their dust distribution. However, the picture from gas observations is much less clear and constraints on the radial gas density structure (i.e. gas gaps) remain rare and uncertain. Aims. We want to investigate the importance of thermo-chemical processes for the interpretation of high-spatial-resolution gas observations of planet-forming disks and their impact on the derived gas properties. Methods. We applied the radiation thermo-chemical disk code PRODIMO (PROtoplanetary DIsk MOdel) to model the dust and gas disk of HD 163296 self-consistently, using the DSHARP (Disk Substructure at High Angular Resolution) gas and dust observations. With this model we investigated the impact of dust gaps and gas gaps on the observables and the derived gas properties, considering chemistry, and heating and cooling processes. Results. We find distinct peaks in the radial line intensity profiles of the CO line data of HD 163296 at the location of the dust gaps. Our model indicates that those peaks are not only a consequence of a gas temperature increase within the gaps but are mainly caused by the absorption of line emission from the back side of the disk by the dust rings. For two of the three prominent dust gaps in HD 163296, we find that thermo-chemical effects are negligible for deriving density gradients via measurements of the rotation velocity. However, for the gap with the highest dust depletion, the temperature gradient can be dominant and needs to be considered to derive accurate gas density profiles. Conclusions. Self-consistent gas and dust thermo-chemical modelling in combination with high-quality observations of multiple molecules are necessary to accurately derive gas gap depths and shapes. This is crucial to determine the origin of gaps and rings in planet-forming disks and to improve the mass estimates of forming planets if they are the cause of the gap.

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The developement of red mud flood environmental information system and the methodology for the spatial analysis of the degraded area

Landscape & Environment ◽

10.21120/le/9/1/1 ◽

2015 ◽

Vol 9 (1) ◽

pp. 1-11

Author(s):

Gábor Bakó ◽

Gábor Kovács ◽

Zsolt Molnár ◽

Judit Kirisics ◽

Eszter Góber ◽

...

Keyword(s):

Remote Sensing ◽

Spatial Resolution ◽

Red Mud ◽

High Spatial Resolution ◽

Three Dimensional ◽

Environmental Information ◽

Evaluation Methodology ◽

Aerial Photogrammetry ◽

Impact Area ◽

The Impact

The red mud disaster occurred on 4th October 2010 in Hungary has raised the necessity of rapid intervention and drew attention to the long-term monitoring of such threat. Both the condition assessment and the change monitoring indispensably required the prompt and detailed spatial survey of the impact area. It was conducted by several research groups - independently - with different recent surveying methods. The high spatial resolution multispectral aerial photogrammetry is the spatially detailed (high resolution) and accurate type of remote sensing. The hyperspectral remote sensing provides more information about material quality of pollutants, with less spatial details and lower spatial accuracy, while LIDAR ensures the three-dimensional shape and terrain models. The article focuses on the high spatial resolution, multispectral electrooptical method and the evaluation methodology of the deriving high spatial resolution ortho image map, presenting the derived environmental information database

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Comprehensive investigation on non-parametric classification methods in order to separate urban objects using the integration of very high spatial resolution LiDAR and aerial data

Journal of Geospatial Information Technology ◽

10.29252/jgit.5.3.77 ◽

2017 ◽

Vol 5 (3) ◽

pp. 77-97

Author(s):

Zinat Ghavami ◽

Hossein Arefi ◽

Behnaz Bigdeli ◽

Milad Janalipour ◽

◽

...

Keyword(s):

Spatial Resolution ◽

High Spatial Resolution ◽

Classification Methods ◽

Comprehensive Investigation ◽

Very High Spatial Resolution ◽

Parametric Classification ◽

Very High ◽

Non Parametric

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Satellite imagery of lengthy territories with complex configuration with the account of attitude and positioning errors

E3S Web of Conferences ◽

10.1051/e3sconf/20197501013 ◽

2019 ◽

Vol 75 ◽

pp. 01013

Author(s):

Dmitriy Mozgovoy ◽

Dmitriy Svinarenko ◽

Roman Tsarev ◽

Tatiana Yamskikh

Keyword(s):

Spatial Resolution ◽

Satellite Imagery ◽

High Spatial Resolution ◽

Program Control ◽

Complex Configuration ◽

Positioning Errors ◽

Satellite Attitude ◽

The Impact

A method for monitoring attitude and positioning errors when taking satellite imagery of lengthy territories with complex configuration using an ultra-high spatial resolution optical-electronic scanner is described in the article. The results of modeling the system of automatic satellite attitude program control during the process of imagery are presented. Given these results, the impact of attitude and positioning errors during satellite imagery was estimated on the coverage percentage of the territory to be imaged.

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Comparison of Canopy Closure Estimation of Plantations Using Parametric, Semi-Parametric, and Non-Parametric Models Based on GF-1 Remote Sensing Images

Forests ◽

10.3390/f11050597 ◽

2020 ◽

Vol 11 (5) ◽

pp. 597 ◽

Cited By ~ 1

Author(s):

Jiarui Li ◽

Xuegang Mao

Keyword(s):

Remote Sensing ◽

Spatial Resolution ◽

High Spatial Resolution ◽

Parametric Model ◽

Canopy Closure ◽

Mean Square ◽

Remote Sensing Images ◽

Estimation Models ◽

Forest Farm ◽

Non Parametric

Canopy closure (CC) is an important parameter in forest ecosystems and has diverse applications in a wide variety of fields. Canopy closure estimation models, using a combination of measured data and remote sensing data, can largely replace traditional survey methods for CC. However, it is difficult to estimate the forest CC based on high spatial resolution remote sensing images. This study used China Gaofen-1 satellite (GF-1) images, and selected China’s north temperate Wangyedian Forest Farm (WYD) and subtropical Gaofeng Forest Farm (GF) as experimental areas. A parametric model (multiple linear regression (MLR)), non-parametric model (random forest (RF)), and semi-parametric model (generalized additive model (GAM)) were developed. The ability of the three models to estimate the CC of plantations based on high spatial resolution remote sensing GF-1 images and their performance in the two experimental areas was analyzed and compared. The results showed that the decision coefficient (R2), root mean square error (RMSE), and relative root mean square error (rRMSE) values of the parametric model (MLR), semi-parametric model (GAM), and non-parametric model (RF) for the WYD forest ranged from 0.45 to 0.69, 0.0632 to 0.0953, and 9.98% to 15.05%, respectively, and in the GF forest the R2, RMSE, and rRMSE values ranged from 0.40 to 0.59, 0.0967 to 0.1152, and 16.73% to 19.93%, respectively. The best model in the two study areas was the GAM and the worst was the RF. The accuracy of the three models established in the WYD was higher than that in the GF area. The RMSE and rRMSE values for the MLR, GAM, and RF established using high spatial resolution GF-1 remote sensing images in the two test areas were within the scope of existing studies, indicating the three CC estimation models achieved satisfactory results.

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An evaluation of the potential of Sentinel 1 for improving flash flood predictions via soil moisture–data assimilation

Advances in Geosciences ◽

10.5194/adgeo-44-89-2017 ◽

2017 ◽

Vol 44 ◽

pp. 89-100 ◽

Cited By ~ 8

Author(s):

Luca Cenci ◽

Luca Pulvirenti ◽

Giorgio Boni ◽

Marco Chini ◽

Patrick Matgen ◽

...

Keyword(s):

Soil Moisture ◽

Data Assimilation ◽

Spatial Resolution ◽

Temporal Resolution ◽

Hydrological Model ◽

High Spatial Resolution ◽

Flash Flood ◽

Soil Moisture Data ◽

Time Period ◽

The Impact

Abstract. The assimilation of satellite-derived soil moisture estimates (soil moisture–data assimilation, SM–DA) into hydrological models has the potential to reduce the uncertainty of streamflow simulations. The improved capacity to monitor the closeness to saturation of small catchments, such as those characterizing the Mediterranean region, can be exploited to enhance flash flood predictions. When compared to other microwave sensors that have been exploited for SM–DA in recent years (e.g. the Advanced SCATterometer – ASCAT), characterized by low spatial/high temporal resolution, the Sentinel 1 (S1) mission provides an excellent opportunity to monitor systematically soil moisture (SM) at high spatial resolution and moderate temporal resolution. The aim of this research was thus to evaluate the impact of S1-based SM–DA for enhancing flash flood predictions of a hydrological model (Continuum) that is currently exploited for civil protection applications in Italy. The analysis was carried out in a representative Mediterranean catchment prone to flash floods, located in north-western Italy, during the time period October 2014–February 2015. It provided some important findings: (i) revealing the potential provided by S1-based SM–DA for improving discharge predictions, especially for higher flows; (ii) suggesting a more appropriate pre-processing technique to be applied to S1 data before the assimilation; and (iii) highlighting that even though high spatial resolution does provide an important contribution in a SM–DA system, the temporal resolution has the most crucial role. S1-derived SM maps are still a relatively new product and, to our knowledge, this is the first work published in an international journal dealing with their assimilation within a hydrological model to improve continuous streamflow simulations and flash flood predictions. Even though the reported results were obtained by analysing a relatively short time period, and thus should be supported by further research activities, we believe this research is timely in order to enhance our understanding of the potential contribution of the S1 data within the SM–DA framework for flash flood risk mitigation.

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Impact of Main Pipe Flow Velocity on Leakage and Intrusion Flow: An Experimental Study

Water ◽

10.3390/w11010118 ◽

2019 ◽

Vol 11 (1) ◽

pp. 118 ◽

Cited By ~ 3

Author(s):

Yu Shao ◽

Tian Yao ◽

Jinzhe Gong ◽

Jinjie Liu ◽

Tuqiao Zhang ◽

...

Keyword(s):

Flow Velocity ◽

Pipe Flow ◽

Pressure Difference ◽

Discharge Coefficient ◽

Pipe Wall ◽

Technical Note ◽

Opposite Pattern ◽

Main Pipe ◽

Pressurized Pipelines ◽

The Impact

The classic orifice equation is commonly used to calculate the leakage and intrusion rate for pressurized pipelines with cracks on the pipe wall. The conventional orifice equation does not consider the effect of the flow velocity in the main pipe, and there is a lack of studies on this matter. For this technical note, the influence of the main pipe flow velocity on the outflow and inflow through a crack on the pipe wall was studied in the laboratory. The experimental results show that the impact of the main pipe flow velocity can be significant. When the pressure difference across the orifice was constant, with the increase of the main pipe flow velocity, the outflow velocity increased, but the contraction area of the jet and the outflow discharge coefficient decreased. By comparing orifices with different shapes, it was found that the discharge from the circumferential crack was most sensitive to the main pipe flow velocity. In addition, the main pipe flow promoted the orifice inflow. When the pressure difference across the orifice was constant, with the increase of the main pipe flow velocity, the inflow discharge coefficient increased, which is the opposite pattern to that of the orifice outflow.

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