The route obtained by RS/GIS method shows 5.7 km saving (13.4%) over the original 42 km alignment obtained by existing survey method. This route after reconciliation has now been accepted as final alignment after ground visits confirmed the feasibility.
| Route Source | Actual Length (m) | Mean cost / unit (Relative) | Total cost (Relative) | Difference (%) (Route length) | Difference (%) (relative cost) |
| Reference route(Survey basedby MMIL, Ahd) | 42572 | 1339.6
(1.00) | 57046480 | 0.00 | 0.00 |
| SAC Route | 36868 | 1334.65
(0.996) | 49205876 | -13.40 | -13.50 |
2. Route plan for Chennai-Bangalore gas pipeline
Projects and Development India Ltd (PDIL) Noida had expressed interest in optimum routing of Chennai-Bangalore pipeline, which was entrusted to them on behalf of Gas Authority of India Ltd (GAIL), New Delhi.
The cost surface search methodology was applied on this important section to further demonstrate the utility of the technique. Twelve cost layers were derived from thematic maps on soil, geology, water bodies, drainage, transport network, elevation model, slope, road distance, land use, forest maps etc on 1:250 000 scale. CWCS was generated using suitable ranks and weightages and route analysis was performed for two points west and east of Chennai and Bangalore respectively using varying material, construction and access cost ratios. Costs were optimized with mean values having relative significant only. Six different routes based on combination of material, construction and access criteria and having up to 12 per cent saving as compared to a straight-line route have been generated.
Benefits : summing up
The method for semi-automated alignment of pipelines using RS and GIS tools has unique advantages like
- Updated and integrated information on terrain,
- Shortest route by automated and computation based search techniques,
- Spatial and numerical data organization of layout,
- Cadastral overlays for route ROU/ROW measures,
- Cost well compensated by high benefits and speedy implementation and
- Downstream options for O&M support.
The method is general enough to be applicable for other sectors related to linear infrastructure planning like alignment of electric transmission lines, network plans for roads and rail etc.
Concluding remarks: Costs
Two different methods of semi-automated alignment of pipelines using RS and GIS tools have been developed and tested. The cost in terms of budget and time for implementing RS/GIS method seems unnecessary at first glance, but the experiments carries out so far indicate its high benefits compared to cost. In fact various studies point towards almost guaranteed saving of 5-15 per cent. As the cost of implementing the method is merely one-thousandth part of the project cost, cost benefit ratio of over 50 is expected in worst case scenario.