RAIL ROUTE ALIGNMENT IN HILLY AREA IN GIS ENVIRONMENT

Abstract

Route survey has been done with the help of topographical maps provided by the Survey of India. In order to identify the possible corridors, contours drawn on the maps are used. Being the two-dimensional representation of three-dimensional world it become very difficult to visualize the terrain using these maps. This problem is enhanced in difficult terrain, such as hilly area. It takes much time to identify the possible corridors and some time not all corridors are identified: With addition it become very difficult and some time erroneous, to read all contour values and performall calculations for each identified alignments. Other problems associated with the topographical maps are Informations are not upto date. For route surveys in hilly terrain Aerial photographs and Satellite imageries with addition to topographical maps of suitable scale may be used to visualize and analyze the area. All these data sources are then compiled and processed using GIS. GIS uses digital inputs, which may be from Aerial photographs, Satellite imageries or may be from topographical map. Information on Topographical sheets is converted into digital form by digitizing the map features and contours. 3D-GIS a specialized branch of the GIS uses contours and -spot levels obtained from topographical sheets or from Aerial photographs or Field survey data, to create a mathematical, model of the terrain. Projecting all the feature.'on this surface of that mathematical model called DTM (Digital Terrain Model). Using this DTM, rendering over the terrain is possible, giving bird's eye view, which help to identify the possible corridors for the route. The information stored . in the form of DTM enables the planner to interrogate-- d obtain elevation of any point on the ?it map. The designer can make a quick decision of th alignment and profile, since the burden of routine calculation of grades, cross-sections and earthwork values is avoided. Thus the GIS enable the designer to examine the various alternative routes in the area, making the difficult terrain, no more difficult. Satellite data are used to update the informations, giving belt \Idea about Land-use/Land-cover of the area. Salellit