Use of water indices in the determination of thermokarst lakes according to remote sensing data

2021 ◽  
pp. 67-74
Author(s):  
Artem Pshenichnikov
Keyword(s):  
Visual Analysis ◽  
Remote Sensing Data ◽  
Water Bodies ◽  
Identical Result ◽  
Spectral Indices ◽  
Quadratic Error ◽  
Thermokarst Lakes ◽  
Ndvi Index ◽  
Water Indices

The results of application of six spectral indices (AWEI, MNDWI, NDVI, NDWI, TCW, WRI) for the isolation of thermokarst lakes in tundra landscapes of northern Yakutia are presented. To assess the accuracy of decryption of lakes, an average quadratic error (MSE) was calculated. The minimum MSE value is 0.11 km2 and corresponds to the NDWI index. An almost identical result (0.12 km2) is found in the WRI index, slightly worse (0.15 km2) one — in the NDVI index. An MNDWI index has the highest mean square error (7.02 km2). Visual analysis also showed better decryption of water bodies using the NDWI, WRI and NDVI indices, which allows the use of these indices for automatical isolatation water bodies.

scholarly journals Detecting the Cool Island Effect of Urban Parks in Wuhan: A City on Rivers

2020 ◽  
Vol 18 (1) ◽  
pp. 132
Author(s):  
Qijiao Xie ◽  
Jing Li
Keyword(s):  
Remote Sensing ◽  
Negative Impact ◽  
Remote Sensing Data ◽  
Urban Parks ◽  
High Water ◽  
Water Bodies ◽  
Green Spaces ◽  
Heat Island ◽  
Island Effect ◽  
Urban Heat

As a nature-based solution, development of urban blue-green spaces is widely accepted for mitigating the urban heat island (UHI) effect. It is of great significance to determine the main driving factors of the park cool island (PCI) effect for optimizing park layout and achieving a maximum cooling benefit of urban parks. However, there have been obviously controversial conclusions in previous studies due to varied case contexts. This study was conducted in Wuhan, a city with high water coverage, which has significant differences in context with the previous case cities. The PCI intensity and its correlation with park characteristics were investigated based on remote sensing data. The results indicated that 36 out of 40 urban parks expressed a PCI effect, with a PCI intensity of 0.08~7.29 °C. As expected, larger parks with enough width had stronger PCI intensity. An increased density of hardened elements in a park could significantly weaken PCI effect. Noticeably, in this study, water bodies in a park contributed the most to the PCI effect of urban parks, while the vegetated areas showed a negative impact on the PCI intensity. It implied that in a context with higher water coverage, the cooling effect of vegetation was weakened or even masked by water bodies, due to the interaction effect of different variables on PCI intensity.

scholarly journals Comparing of Landsat 8 and Sentinel 2A using Water Extraction Indexes over Volta River

2017 ◽  
Vol 10 (1) ◽  
pp. 1 ◽  
Author(s):  
Clement Kwang ◽  
Edward Matthew Osei Jnr ◽  
Adwoa Sarpong Amoah
Keyword(s):  
Remote Sensing ◽  
Satellite Images ◽  
Remote Sensing Data ◽  
Unsupervised Classification ◽  
Water Bodies ◽  
Water Extraction ◽  
Landsat 8 ◽  
Sensing Data ◽  
Optimal Classifier ◽  
Sentinel 2A

Remote sensing data are most often used in water bodies’ extraction studies and the type of remote sensing data used also play a crucial role on the accuracy of the extracted water features. The performance of the proposed water indexes among the various satellite images is not well documented in literature. The proposed water indexes were initially developed with a particular type of data and with advancement and introduction of new satellite images especially Landsat 8 and Sentinel, therefore the need to test the level of performance of these water indexes as new image datasets emerged. Landsat 8 and Sentinel 2A image of part Volta River was used. The water indexes were performed and then ISODATA unsupervised classification was done. The overall accuracy and kappa coefficient values range from 98.0% to 99.8% and 0.94 to 0.98 respectively. Most of water bodies enhancement indexes work better on Sentinel 2A than on Landsat 8. Among the Landsat based water bodies enhancement ISODATA unsupervised classification, the modified normalized water difference index (MNDWI) and normalized water difference index (NDWI) were the best classifier while for Sentinel 2A, the MNDWI and the automatic water extraction index (AWEI_nsh) were the optimal classifier. The least performed classifier for both Landsat 8 and Sentinel 2A was the automatic water extraction index (AWEI_sh). The modified normalized water difference index (MNDWI) has proved to be the universal water bodies enhancement index because of its performance on both the Landsat 8 and Sentinel 2A image.

scholarly journals Estimation of Infiltration Volumes and Rates in Seasonally Water-Filled Topographic Depressions Based on Remote-Sensing Time Series

Sensors ◽  
2021 ◽  
Vol 21 (21) ◽  
pp. 7403
Author(s):  
Pavel P Fil ◽  
Alla Yu Yurova ◽  
Alexey Dobrokhotov ◽  
Daniil Kozlov
Keyword(s):  
Remote Sensing ◽  
Time Series ◽  
Shallow Groundwater ◽  
Remote Sensing Data ◽  
Water Bodies ◽  
Water Infiltration ◽  
Temporary Ponds ◽  
Small Water ◽  
Negative Exponential ◽  
Topographic Depressions

In semi-arid ecoregions of temperate zones, focused snowmelt water infiltration in topographic depressions is a key, but imperfectly understood, groundwater recharge mechanism. Routine monitoring is precluded by the abundance of depressions. We have used remote-sensing data to construct mass balances and estimate volumes of temporary ponds in the Tambov area of Russia. First, small water bodies were automatically recognized in each of a time series of high-resolution Planet Labs images taken in April and May 2021 by object-oriented supervised classification. A training set of water pixels defined in one of the latest images using a small unmanned aerial vehicle enabled high-confidence predictions of water pixels in the earlier images (Cohen’s Κ = 0.99). A digital elevation model was used to estimate the ponds’ water volumes, which decreased with time following a negative exponential equation. The power of the exponent did not systematically depend on the pond size. With adjustment for estimates of daily Penman evaporation, function-based interpolation of the water bodies’ areas and volumes allowed calculation of daily infiltration into the depression beds. The infiltration was maximal (5–40 mm/day) at onset of spring and decreased with time during the study period. Use of the spatially variable infiltration rates improved steady-state shallow groundwater simulations.

scholarly journals CNN-based visual analysis to study local boiling characteristics

2021 ◽  
Vol 2119 (1) ◽  
pp. 012068
Author(s):  
A N Chernyavskiy ◽  
I P Malakhov
Keyword(s):  
Network Architecture ◽  
High Speed ◽  
Visual Analysis ◽  
Nucleation Site ◽  
High Speed Video ◽  
Site Density ◽  
Segmentation Approach ◽  
Nucleation Site Density ◽  
Instance Segmentation

Abstract Visual analysis allows an estimate of different local boiling characteristics including bubble growth rate, departure diameters and frequencies of nucleation, nucleation site density and evolution of bubbles and dry spots in time. At the same time, visual determination of the presented characteristics in case of big amounts of data requires the development of the appropriate software which will allow not only determination of bubble location, but also an estimate of their sizes based on high-speed video. The presented problem can be solved by using the instance segmentation approach based on a convolutional neural network. In the presented work Mask R-CNN network architecture was used for estimation of the local boiling characteristics.

Determination of Relation between the Quaternary Sediments and Land Use Dissemination on the Basis of Šventoji River Basin

2017 ◽  
Author(s):  
Andrius Litvinaitis ◽  
Lina Bagdžiūnaitė-Litvinaitienė ◽  
Laurynas Šaučiūnas
Keyword(s):  
Land Use ◽  
River Basin ◽  
Water Bodies ◽  
Quaternary Sediments ◽  
Corine Land Cover ◽  
Quality Of Water ◽  
Management Plans ◽  
Subsurface Runoff

On preparing of the first management plans of River Basin Districts have been found that diffuse agricultural pol-lution is one of the most important causing factor and the most significant impact on the quality of water bodies. Diffuse agricultural pollution can be from 45% to 80% of nitrate nitrogen pollution load of water bodies. Pollution is transported by water surface and subsurface runoff through sediments from agricultural territories. This article aims at evaluating of relation between the Quaternary sediments and Land use dissemination. The lithological factor (sandy, loamy, argillaceous) of the basin was calculated based on Quaternary map of Lithuania M 1:200000 and Lithuanian river map M 1:50000. The land-use factor of the basin was calculated based on Corine Land cover M 1:100000 using ArcGis software. In order to carry out more thorough analysis of the determination of relation between the Quaternary sediments and Land use dissemination in given territories, sections of 0–50 m, 50–200 m, 200–500 m, 500–800 m, 800–1000 m and >1000 m were established, calculating the distance in meters from the riverbank.

Efficacy of the Touch Technique for Surface and Foot-Placement Preview

1997 ◽  
Vol 91 (1) ◽  
pp. 47-52 ◽  
Author(s):  
S.J. LaGrow ◽  
B.B. Blasch ◽  
W. De L'Aune
Keyword(s):  
Relative Position ◽  
Visual Analysis ◽  
Focal Point ◽  
Foot Placement ◽  
Exact Determination ◽  
Orientation And Mobility

Seven orientation and mobility specialists were videotaped simultaneously on three stationary cameras while traveling with long canes. The cameras were calibrated to allow for the exact determination of the relative position of the various body and cane parts as the travelers passed through the coordinated focal point. Input from the videotapes was digitized and entered on a computer to provide continuous traces of movement. A visual analysis of the traces indicated that the cane tip consistently touched outside the foot (and therefore did not provide foot-placement preview) and that surface preview was inconsistent.

The Distribution of Diatom in the Five Lakes along the Yangtze River

2013 ◽  
Vol 850-851 ◽  
pp. 1309-1312
Author(s):  
Yu Zhou ◽  
Quan Yu ◽  
Wei Hang ◽  
Yu Zhong Wang ◽  
Hui Pin Wang ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Water Samples ◽  
Yangtze River ◽  
Water Bodies ◽  
The Yangtze River ◽  
Significant Difference ◽  
The Future ◽  
Scanning Electron

In order to investigate the diatom distribution in the five lakes along the Yangtze River, and discuss the significance for the diagnosis of drowning. 6 water samples were collected in the five lakes along Yangtze River in June, 2012. Subsequently, The genus and the quantity of the diatoms in the water samples were investigated using scanning electron microscopy (SEM). The result showed us that there was significant difference between the waters sampled from the different sites . These data on diatom distribution are helpful to the diagnosis of the cause of the death as well as to the determination of the drowning site in cases of drowning. Therefore, it is necessary to develop the database of diatoms in more extensive water bodies for the forensic diagnosis of drowning in the future.

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