6.13　Survey of Earth Electrode Site

6.13.1　The survey of earth electrode site should include horizontal and elevation control survey，topographic survey of land and water areas，survey of investigation points and lines，and the plans and sections of earth electrode rings.

6.13.2　Uniform national or local horizontal and elevation systems or the horizontal and elevation systems used for urban planning should be used for the survey of electrode site.

6.13.3　The precision of first-order horizontal control shall not be lower that of first-order traverse.The methods and precision indicators of horizontal control survey shall conform to the relevant provisions in the national standard in force GB 50026 Code for Engineering Surveying.The precision of first-order elevation control shall not be lower than that of mapping leveling or Level 1 electro-optical distance measurement trigonometric leveling.The methods and precision indicators of elevation control survey shall conform to the provisions in 6.5.6.

6.13.4　For the survey of topographic map of electrode site，the methods and technical requirements shall conform to the relevant provisions in the national standard in force GB 50026 Code for Engineering Surveying.The scale for topographic maps of land and water areas should be 1∶1000 or 1∶2000.

6.13.5　Permanent marks with numbers should be buried at the center point of electrode rings，starting points of plans and sections of external electrode ring and internal electrode ring，and their coordinates and elevations shall be surveyed in the field.

6.13.6　For the internal and external electrode rings and the laying route of injection shunt cables，the plans and sections shall be surveyed in the field，and the strip-type topographic maps with a scale of 1∶500 or 1∶1000 may be surveyed if necessary.

6.13.7　For the survey of longitudinal sections of electrode rings and laying route of cables，the selected section points shall accurately reflect the terrain variation and landform features along the direction of route，and the spacing between adjacent section points shall not be larger than 20m.The RMSE of elevation at section points shall not be larger than±0.3m.

6.13.8　The annular route shall be unfolded to a line to draw the plans and sections of electrode rings，for which the scale should be 1∶2000（transversal）and 1∶200（longitudinal），and the expression shall conform to the provisions in Appendix F of this code.

6.13.9　The plans and sections between the two towers at electrode site and the center of ring shall be developed separately.

6.13.10　The engineering geophysical prospecting points，exploration points，and profiling lines should be surveyed at the nearest control points by means of polar coordinate method with total station or GPS positioning method，and the corresponding survey marks shall be established in the field.

6.13.11　The elevations of geophysical exploration and prospecting points and profiling lines should be surveyed using the methods of EDM trigonometric leveling or GPS elevation-fitting.

6.13.12　The horizontal coordinates of geophysical exploration and prospecting points and profiling lines may be rounded up to 0.1m and elevation to 0.01m.