Evaluation of the Use of Remote Sensing Techniques for Highway Alignment Layout

Abstract

The present research represents the ability of using the remote sensing techniques in highway engineering field throughout the evaluation process for road alignment that is considered in the study (Emam–Waise detour). This road lies between Al-Mukdadiyah and Khaneqeen towns connecting Al-Sa’adyah and Ibraheem Al- Somayda’ay villages along that alignment in the eastern part of Iraq. The research idea focuses on an evaluation process for the alignment in reconnaissance and preliminary planning stages depending on the compression process between the used conventional method which represents field survey operations and the new method which depends on remote sensing techniques and Digital Terrain Model design (DTM), through using of the most important programs in Geographical Information System (GIS). A Landsat (Thematic Mappar ) image taken for the study area is used in the analytical part of the work after some pre-processing for the image , including the enhancement process that helps us in data collection steps, especially in the determination of Ground Control Points (GCPs) which are distributed in the region. The study is also concerned with dividing the work into two main parts: The first one represents road field survey measurements that lie on the road centerline and sides (5m distance from each side). The second part of the work represents a (DTM) design, which gives three- dimensions (E, N, H) for each point in the region. A method for digital terrain model design is adopted, it is called (scanned contour lines) method, which depends on the topographic map of the study area of (1:100.000) scale and (10 m) contour interval , also using GIS program (Arc view, ver.3.1). A comparative study was conducted between the field measured coordinates and the corresponding coordinates extracted from digital model through plotting a longitudinal profile for field and DTM measurements together having the same scale, based on differences of heights. The study shows that the coincidence ratio between the two methods is 82%. After correcting the value of the contour interval of the base map that contains an error in contour interval values, the coincidence ratio between the two methods was increased to 95%.