Geodesy, Engineering Surveys, and Site Preparation
Survey types
Engineering surveys include topographic, geodetic, geological, hydrological, and environmental investigations. Each has its own scope and reporting requirements. Candidates must know the purpose of the geodetic control network, the setting-out of axes, and the as-built survey that verifies completed structures against design.
Setting-out and accuracy
Understand the instruments: total station, level, theodolite, GNSS. Know the concepts of reference point, benchmark, and the tolerance for axis deviation. The setting-out act fixes the position of the main axes and must be signed before main works begin. As-built surveys are mandatory for hidden and completed elements.
Traps
- Confusing the topographic survey (existing conditions) with the setting-out survey (design transfer).
- Assuming the contractor can choose tolerances; they are defined by normative documents.
- Forgetting that benchmarks must be tied to the state geodetic network.
- Mixing up the as-built survey with the acceptance act - both are needed.
Worked example
A column axis deviates 12 mm from design where the tolerance is 10 mm. The element is non-conforming; the correct response is to document the deviation, notify the designer, and obtain a decision on correction or acceptance with justification. It is not acceptable to record the deviation and proceed.
Rule of thumb
Before any main work: verify the geodetic control, sign the setting-out act, and confirm the benchmarks are tied to the state network.