5.1　General requirements

5.1.1　Prior to survey，survey scheme shall be prepared，site reconnaissance shall be carried out，relevant survey data shall be received and collected，the handover for survey data shall be handled，and the existing survey control points shall be resurveyed and protected.

5.1.2　The survey records，calculation results，graphs and tables shall be clearly written and completely signed and shall be rechecked.

5.1.3　The locations of the survey stakes and points shall be favorable for protection，identification，ease of use，and location confirmation.Multiple points shall not be put on one single stake.

5.1.4　During construction，the allowable centerline error of the tunnel and the cavern shall comply with the requirements in Table 5.1.4.

5.1.5　When a new point is added on basis of an existing control point，the new point shall be rechecked and shall not be used untill it is qualified.

5.1.6　The survey control network shall be resurveyed regularly during construction. M1SmHSDyR3jk60id1evBfxA8BLo3qVeJPj9WMEYw4ndyCadesCCqQf7OwyFN5Vwz