Lineament study in the Björkö area satellite radar and airbome VLF data- possible tools for groundwater prospecting
Abstract: This thesis work mainly concerns lineament study, that is the extraction and analysis of lineaments from satellite radar and airborne VLF data using GIS to explore potential aquifers or groundwater locations associated in the study area (Björkö) situated west of Stockholm in the lake Mälaren. The other objective focuses on improving the general knowledge of hydrology, more importantly techniques and methods in lineament analysis. The airborne VLF data for the Björkö area was received in the xyz-coordinate format. The data have been put into a 50 m grid (spatial resolution of 50 m) and was converted into Idrisi format using the analysis software Idrisi 32. The data was then analysed and classified into different categories based on the relative anomaly amplitude followed by on-line digitisation of suspected anomalies in each category. The anomalies from the different categories that were interpreted as lineaments were further added as a single overlay. The radar data was originally received in the Ascii version (a Grass file format). The data have been put into a 50 m grid (spatial resolution of 50 m). The data was then converted into Idrisi format using the Idrisi 32-analysis software. A series of filtering operations in Idrisi were further carried out on the generated radar image from the conversion in order to enhance it for digitisation. Different directional images resulted from the filtering operation and were used for the digitisation of suspected anomalies interpreted as lineaments. The result from the VLF operation shows different conductivity levels in anomalies that have been interpreted as lineaments depicting possible fracture zones in the bedrock from good conductors to weak conductors in the Björkö region. Lineaments derived from the radar data represent terrain escarpments that may be related to fracture zones. The obtained result from the maximum filtering represent terrain features at high angle to the radar incident signal. Also terrain features with a low angle to the radar incident signal were produced from the minimum filtering operation. The methods employed in the study have been successful in identifying possible fracture zones in the study area and can subsequently be applied in groundwater prospecting analysis.
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