6.6　Survey of Plans and Sections

6.6.1　Where required by the design，the plans of relative positions of the lines going in and out of a substation shall be collected or surveyed.When the plans of ingoing and outgoing lines of a substation or power plant need to be surveyed and mapped，the scale can be 1∶1000 or 1∶2000.The plans of ingoing and outgoing lines shall adopt the same coordinate system as the substation or power plant.For the cartographic symbols for plans of incoming/outgoing lines of a substation or power plant，refer to Appendix C.

6.6.2　Before the survey of plans and sections，relevant basic information shall be available，including:turning angles of the sections to be measured，distances of line centerline to the sidelines required by the design discipline，width of horizontal measurement，maximum wind slanting distance，and map scale.

6.6.3　For the survey of plans and sections，the straight route shall take the backsight direction as 0° and foresight direction as 180°.When establishing a station at an angle stake to survey section points in the foresight direction，the surveyors shall set the horizontal circle at 180° and aim at the foresight direction.The bisecting line of the turning angle shall be taken as the boundary of survey scope for section points in foresight and backsight direction.

6.6.4　Where the plans and sections start from or end at a substation，the ground elevation of its centers shall be indicated and the crossarm elevation of existing attachment points of the conductors shall be surveyed and noted in response to the design requirements.In case of segmental survey，the relative elevation of stake at the junction of two segments shall be noted and described on the map.

6.6.5　Total station，GPS or aerial photographing may be used for the survey of plans and sections.

6.6.6　The following requirements shall be satisfied when a total station is used for the survey of plans and sections:

1　The total station shall be of Class DJ6 or above，the index error of vertical circle shall not exceed 1，and the constant of prism for photoelectric distance measurement shall be corrected.

2　Sketches shall be drawn on site.

3　Section points should be observed at the nearest stake.The length of the measured distance should not exceed 800m for a surface feature，and not exceed 1000m for a landform point.Otherwise，one observation set with the telescope in normal position shall be necessary，for which the relative error of distance discrepancy shall not be more than 1/500，the discrepancy of vertical angles shall not be more than 1，and the median shall be taken as the final result.

4　In case of large spacing between two stakes or complicated topographic conditions or surface features，temporary stations shall be established.When using a total station to establish a temporary observation station，the surveyors shall make two observation sets in the same or opposite directions，for which the relative error of distance discrepancy shall not exceed 1/1000 and the tolerance of elevation differences shall be 0.3m.

6.6.7　The following requirements shall be satisfied when RTK GPS is used for the survey of plans and sections:

1　The precision of RTK CPS instruments shall not be lower than 5cm.

2　Sketches shall be drawn on site.

3　In the original RTK GPS 3D coordinates，the indices of horizontal and elevation precision shall be maintained.

6.6.8　The following requirements shall be satisfied when aerial survey is used for plans and sections:

1　Relevant data shall be available before the survey of plans and sections，including the adjustment calculation of aerial triangulation densification，and the parameters of photographs，the coordinates values of turning angles after the route is determined in the field shall be taken as the starting and end point data of linear sections.

2　The parameters of camera and mapsheet and the distances of slide traverses shall be set up correctly and the coordinates of turning angles shall be imported or input correctly.

3　Data about sections can be collected manually or by means of automatic scanning.For flat and hilly areas，automatic scanning should be used.During automatic scanning，the stereomodel shall be traced manually.The scanning step should be in the range of 5-10m（actual distance）.The scanning pitch is the perpendicular distance from side conductors to the center conductor，and the number of conductors is three，e.g.，the center conductor，left side conductor and right side conductor.Manual mode should be used for mountainous areas.

4　The sections shall be edited on line and the data files and graphic files submitted shall be consistent.The map decoration，text lettering and map sheet joining should be edited offline.

5　The operator shall not be changed within one segment.

6　The format conversion shall not cause any data loss.

6.6.9　All buildings（structures），roads，pipelines，rivers，reservoirs，ponds，ditches，channels，graveyards，bluffs and cliffs within the specified scope on both sides of the route centerline，which may affect the lines，shall be actually surveyed with instruments and indicated on the plans.

6.6.10　Where the lines run through forests，orchards，nursery gardens，crops and cash crop areas，their boundaries and heights of trees shall be actually surveyed and indicated on the plans and sections.

6.6.11　Where the lines are parallel adjacent to communication lines or underground optical cables，the relative positions shall be actually surveyed or annotated with the scale of 1∶1000 or 1∶2000 according to the design requirements.For the sample of the plans of relative positions，refer to Appendix E of this code.

6.6.12　The section points selected to survey shall be able to truthfully reflect the topographical changes and landform features.The spacing between section points in flat areas should not be larger than 50m.On top of isolated hills，there shall be at least three section points.In the areas where the distance between conductors and the ground may possibly cause dangerous effects，the section points shall be appropriately densified.For areas where the safe distance between conductors and the ground is not affected，such as valleys and deep trenches，the surveying may be eliminated，and interruption is allowed in the drawings.

6.6.13　In case of a slope with the aspect ratio more than 1∶3 beyond the side conductors，the wind slanting sections or points shall be surveyed and mapped.The wind slanting sections shall have identical horizontal and vertical scale of 1∶500 or 1∶1000，and the central section point should be taken as the base point of mapping.If the central section point is in a deep cavity for which survey is not needed，the section of side conductor may be taken as the base point of mapping.Where the route is skew with mountain ridges，more than two wind slanting points shall be surveyed.

6.6.14　Any terrain or surface feature between the side conductors on both sides，which is 0.5m higher than the central section and side conductors，shall be surveyed and indicated on the maps.

6.6.15　If the terrain of side conductors is 0.5m higher than the central section，the sections of side conductors shall be surveyed with the surveying positions depending on the side conductor spacing determined by design personnel.When the route runs through gentle slopes，terraced fields，ditches/channels，and dykes/dams，the section points on side conductors which may impose effects shall be surveyed.

6.6.16　When the route runs through a crowded area，the plans of 1∶1000 or 1∶2000 may be mapped as required for design.For the sample of plans of crowded areas，refer to Appendix A of this code.

6.6.17　The plans and sections of lines should be in the horizontal scale of 1∶5000 and vertical scale of 1∶500.For the sample of plans and sections of power transmission lines，refer to Appendix F of this code.

6.6.18　The plans and sections mapped shall，based on the field data and sketches and，according to the regulation in Appendix G，reflect the locations and elevations of surface features and terrain points accurately and faithfully.The maps shall be clear and beautiful.

6.6.19　When the plans and sections obtained through aerial photographing are edited，the actually surveyed results shall be used for correction purposes，including the distances between straight-line stakes，elevations of angle stakes and straight-line stakes，and the survey results of crossing-over，and the annotation data shall be transferred to the plans and sections.