GB/T 35637-2017 in English

Interpretation of the core content of the standard

As the national standard in the field of urban surveying and mapping, GB/T 35637-2017 has built a complete technical framework system. The standard contains 10 chapters and 20 referenced standards, mainly regulating the following core contents:

Detailed explanation of key technical indicators

5.1 Requirements for space-time benchmarks

Chapter 5 of the standard stipulates a unified space-time benchmark:

• Plane benchmark: 3° Gaussian projection is preferred (central meridian can be customized)
• Elevation benchmark: 1985 National Elevation Benchmark, the theoretical lowest tide surface is used in the sea area
• Special circumstances: It is allowed to establish an independent coordinate system but it must be linked to the national benchmark

6.3 Plane control network architecture

Innovatively propose a three-level control network structure:

Key points for the implementation of special surveying and mapping

8.3 Underground space surveying and mapping

In response to the development needs of urban underground space, the standard requires:

1. Establish a three-level control system of "ground-connection-underground"
2. Surveying and mapping content should include plan views, comprehensive maps, and cross-section views
3. 3D modeling must comply with GB/T 35636 specifications

9.3 Geographic Information Public Platform

Innovatively propose three versions of data service models:

Standard Implementation Suggestions

1. New projects must use the 2000 National Geodetic Coordinate System
2. The LOD level for 3D modeling should be selected according to the application scenario (LOD2 is recommended for conventional planning)
3. Quality control strictly implements the "two-level inspection, one-level acceptance" system
4. Regularly re-test the control network (recommended cycle ≤ 3 years)

Note: During the implementation process, special attention should be paid to the calibration requirements of equipment such as GNSS receivers and total stations, as well as the 3D model accuracy indicators specified in Chapter 7.6.