Final location and detailed survey

The final location and detailed survey transfers the alignment chosen in the preliminary survey to the ground and collects all the data needed for design, estimating and construction.

Process

1. Location of the centre line: the centre line from the plan is set out with a theodolite/total station and fixed by pegs at about 50 m intervals in plain and rolling terrain and 20 m in hilly terrain.
2. Setting out of curves: tangents are fixed at the points of intersection; circular and transition curves are set out by deflection angles/coordinates, and the curve data are recorded.
3. Levelling: the final longitudinal profile; cross-sections at about 50-100 m intervals in plains, 50-75 m in rolling and 20 m in hilly terrain (and at changes of slope); temporary bench marks at about every 250 m.
4. Reference pillars are fixed outside the construction limits so that the centre line can be restored.

Works to be carried out

• Detailed topographic survey at bridges, intersections, hairpin bends and difficult sections (scale 1:500 to 1:1000 near structures).
• Soil survey: soil testing for the subgrade and for borrow areas; CBR values.
• Hydrological survey: catchment area, flood levels, discharge and waterway needs for culverts and bridges.
• Geological/geotechnical investigation for slopes, cuts and fills, and the foundations of structures.
• Material survey: quarries, sand, aggregates, water and their lead distances.
• Land and property survey: land boundaries, structures to be removed, utility lines.
• Traffic survey if required.

Data collected and outputs

Plan and profile drawings, cross-sections, culvert/bridge details, soil data, material sources, quantities, cost estimate, specifications and tender documents.