Abstract:
Construction of a new road usually required a complete layout plan, which is followed by road construction. This layout plan is prepared by road planners and surveyors, equipped with expensive survey instrument and requires large amount of resources in term of money, time and physical force to survey the whole area. Later, planners have to design multiple layouts manually by taking multiple criteria into account e.g. topography, slopes, wetlands, economic feasibility and environmental consequences. After design, designers have to analyze these layouts to find out the best route alignment. This task is cumbersome, iterative and prone to human errors because of concentrating on multiple criteria at same time. In this study, free geo-spatial data sets which includes Landsat 8 satellite imagery and ASTER GDEM has been used to aid the conventional route alignment process. Land use-Land cover classified map was derived from Landsat imagery. Aster GDEM was used to get different derivatives which include slope and drainage pattern of study area. These derivatives were used as criteria, were reclassified and weighted sum together to form an integrated data layer called "friction map". Reclassifying a criterion and assigning weights to criteria is dependent on experts' understanding of problem. "r.walk", a Grass GIS module, has been used to from accumulated cost map from friction map and DEM. Later "Least cost path" has been used to form a route alignment between source and destination point. Different route alignment were created using different criterion reclassifying schemes and changing relative weights. Results show that freely available geospatial data and open source free software can help in reducing the complexity involved in traditional route alignment techniques and can also play significant role in reducing the cost of preliminary survey of area by narrowing down the area of interest from large spatial extent to small area.
