scholarly journals Sub-Surface Investigation Using Vertical Electrical Sounding: Chennai Metropolitan Area

2018 ◽  
Vol 13 (3) ◽  
pp. 317-330 ◽  
Author(s):  
J. SARAVANAN ◽  
KISHAN SINGH RAWAT ◽  
SUDHIR KUMAR SINGH

The data or information on the sub-stratum, nature of aquifers, their spatial disposition, their hydrogeological characteristics and other information, are limited particularly in urban context. The study was performed in the Chennai metropolitan area. The objective of the study was to get the sub-surface information of the study area. The vertical electrical sounding was performed at ninety locations to identify the sub surface lithology. The Archaeans consisting of Charnockites, gneisses and dolerite occupy the southern part of the Metropolitan area. The lower portion of gondwanas belonging to the Talchir beds consist of light brown and green colored Shales occurring below the alluvium in the area between Nandanam on the east to Nandambakkam on the west. These Shales are overlying the older crystalline rocks. The lower portion of gondwanas belonging to the Talchir beds consist of light brown and green coloured Shales occurring below the alluvium in the area between Nandanam on the east to Nandambakkam on the west The Tertiary bed comprising friable white and reddish brown Sandstone occurs on the western side near Chembarambakkam and on the northwestern side between Thirunindravur and Villiwakkam. The thickness of the alluvium ranges between 5m on the southern side to a little more than 20m on the east central part of the Metropolitan area.

2016 ◽  
Vol 34 (1) ◽  
Author(s):  
Walter Sydney Dutra Folly ◽  
Aracy Sousa Senra

ABSTRACT. We describe the construction and testing of a simple and efficient low-cost resistivimeter designed for use in practical classes in Applied Geophysics. The equipment was successfully tested in a vertical electrical sounding (VES) performed on sandy terrain within the campus of the Universidade Federal de Sergipe, Brazil. The VES results were in good agreement with the profiles obtained from two boreholes located approximately 500 m from the test area, clearly demonstrating the efficiency of the equipment and the adopted methodology.Keywords: vertical electrical sounding, electrical resistivity, resistivity profile. RESUMO. Neste artigo, descrevemos a construção e o teste de um resistivímetro de baixo custo, simples e eficiente, concebido para ser utilizado em aulas práticas de Geofísica Aplicada. O equipamento foi testado com a realização de uma sondagem elétrica vertical (SEV) em um terreno arenoso localizado no campus da Universidade Federal de Sergipe, Brasil. Os resultados obtidos nesta SEV apresentaram boa concordância com os perfis observados em dois poços de sondagem localizados a 500 m da área de teste, fato que comprovou a eficiência do equipamento e da metodologia adotada.Palavras-chave: sondagem elétrica vertical, resistividade elétrica, perfil de resistividade. 


2021 ◽  
Vol 14 (6) ◽  
Author(s):  
Emmanuel Tochukwu Omeje ◽  
Desmond Onyeka Ugbor ◽  
Johnson Cletus Ibuot ◽  
Daniel Nnemeka Obiora

2018 ◽  
Author(s):  
Ryan Fry ◽  
Connor Parks ◽  
Mark Meadows ◽  
Rhett Herman

2021 ◽  
Author(s):  
Alan García-Haro ◽  
Josep Roca

<p>In recent years, the use of remote sensed NDVI has become recurrent in urban studies regarding the adaptation of cities to climate change. However, due to the physical diversity within cities and the different resolution offered by the sensors, the territorial interpretation of what the NDVI values really mean becomes difficult. Where the larger the size of the cells of the image, the greater the number of elements of the built environment within it, and the more complex the interpretation becomes.</p><p>In this work, the relationship between the NDVI of three sensors with different cell resolution for the same location and date is studied. In particular, the city of Granollers in the Metropolitan Area of Barcelona is analyzed. First, the NDVI images were obtained from Landsat-8 with 30m resolution, Sentinel-2 with 10m and from the Ministry of Agriculture, Livestock, Fisheries and Food of Catalonia (DARP) with 0.125m resolution. Then, the comparison was performed with a sample of five different typologies of the territory: dense urban core, suburban, industrial, area of highway and rural.</p><p>As first results, a supervised classification of the DARP image allowed the definition of 0.30 as the precise minimum value of NDVI that indicates the actual presence of vegetation. On the other hand, the comparison indicates that, in the urban context, the larger the cell size, the presence of vegetation quality is overestimated, where the higher percentage of cells is concentrated in higher NDVI values than in those with lower resolution. However, this behavior is not appreciated in rural areas, where higher percentages of cells of different resolutions were concentrated in the same NDVI ranges.</p><p>In such a way, it is corroborated that it is in the urban context where this indicator has a greater difficulty of territorial interpretation. Statements that are analyzed in greater depth in this study, where its implications in the use of NDVI in urban studies for the adaptation of cities to climate change are discussed.</p>


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