GB/T 35636-2017 in English

Analysis of standard technical framework

Technical module	Core requirements	Accuracy indicators
Control measurement	Establishment of ground/underground control network, connection measurement	Plane≤50mm, elevation≤20mm
Current situation surveying and mapping	Feature point collection, comprehensive map production	1:500-1:2000 scale
3D modeling	LOD classification, texture mapping	Optimization control of the number of triangle faces

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Key technical points

1. Unification of time and space benchmarks

Article 4.1 of the standard clearly stipulates that the unified urban plane coordinate system (such as CGCS2000) and elevation benchmark (such as the 1985 National Elevation Benchmark) must be adopted to ensure seamless connection of ground and underground data. A typical example is that the Shenzhen Metro project adopts the Shenzhen independent coordinate system unified throughout the city.

2. Accuracy control system

Article 4.2Establish accuracy control with mean error as the core:

• Ground control point: plane ≤50mm, elevation ≤20mm
• Azimuth difference of contact measurement ≤30″
• Mean error of gyro orientation ≤12″

Double well orientation or gyro-assisted measurement can be used under special working conditions.

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Special requirements for 3D modeling

Implementation suggestions

Key points of quality control

According to the requirements of Chapter 10:

• Implement a two-level inspection and one-level acceptance system
• Database construction needs to pass the GB/T 21740 test
• System acceptance should include stress testing and safety assessment

It is recommended to establish a special quality inspection ledger to record process data.

Technology development prospects

This standard is the first national standard for underground space surveying and mapping in China. In the future, it can be combined with:

• BIM+GIS fusion technology
• Mobile laser scanning system
• Real-life 3D China construction requirements

for dynamic update and improvement.