4　Survey

4.0.1　The measuring apparatus and gauges must be checked before measuring.The minimum angle reading of theodolite shall not be larger than 1′.

4.0.2　Check survey of lines must be carried out according to the design data prior to locating of foundation pits.

4.0.3　In case of any of the following conditions during check survey，the causes shall be investigated and deviations shall be corrected:

1　The transverse deviation is more than 50mm taking two adjacent intermediate piles as benchmark.

2　The deviation of the longitudinal distance between central piles of two adjacent towers from the design value is larger than 1% of the design span.

3　The angle deviation of angle piles from the design value is larger than 1′30″when direction observation is used in check survey.

4.0.4　The following types of elevation shall be focused during check survey:

1　Elevation of bulge places where the clearance distance between conductors and the ground（including wind deflection）may be insufficient.

2　Elevation of over-crossing objects between towers.

3　Relative elevation of two adjacent towers.

Comparing to the designed values，the measured value deviations shall not be more than 500mm；otherwise，the causes of deviation shall be investigated and deviations shall be corrected.

4.0.5　The lost particular central piles of towers shall be supplemented based on design data.The relative deviation shall not exceed 1/200 for same-direction observation and not exceed 1/150 for opposite direction observation.

4.0.6　For displacement of central piles of towers，the survey accuracy shall comply with the following provisions:

1　If steel tape measurement is used，the difference between two measurements shall not exceed 1‰of the measured distance.

2　If stadia method is used，the difference between two measurements shall not exceed 5% of the measured distance.

3　If direction observation is used for angle measurement，the difference between measurements of two observation sets shall not exceed 1′30″.

4.0.7　During locating of foundation pits，necessary ancillary piles shall be made to provide convenience for construction and quality control，which shall be positioned in accordance with the location of central piles of towers.The survey accuracy shall meet requirements of standards for construction accuracy.For central piles of towers that can not be reserved during construction，reliable ancillary piles must be made and their locations shall be recorded so as to restore the central piles concerned.

4.0.8　Central piles of angle towers shall meet design requirements in respect of displacement.

4.0.9　The safe distance requirements of design documents for erection of lines must be satisfied.

4.0.10　Where GPS is to be used，the designer shall provide corporation for verification or inspection.