CH/Z 9026-2018 in English

Analysis of the technical framework of the standard

CH/Z 9026-2018, as my country's first special standard for digital water depth model (DBM), has built a complete technical system from data collection to application of results. The standard innovatively adopts a secondary accuracy grading mechanism (A/B level) to achieve quantitative control through the grid point depth mean error indicator, among which the A-level accuracy requirement for 1:500 scale is ±0.15m.

Key technical requirements

Mathematical benchmark system

The standard stipulates the use of the 2000 National Geodetic Coordinate System and the 1985 National Height Datum, and the depth datum must use the local theoretical lowest tide level. For the projection method, the 1:5000 scale uses the 3° zoned Gauss-Krüger projection to ensure seamless connection with land terrain data.

Data quality control

• Blank area identification: The area where data cannot be obtained needs to be assigned a value of -99999 and described in the metadata
• Edge tolerance: The difference in water depth values of the same grids in the overlapping area of adjacent maps is ≤1 depth unit
• Metadata specification: Contains 81 required items (such as grid arrangement method, depth datum unit, etc.)

Implementation and application suggestions

Technology Evolution Direction

Compared with GB 12327-1998 Hydrographic Survey Specification, this standard has made a breakthrough in incorporating inland waters into its scope of application, and introduced the concept of water depth estimation area, reserving interfaces for new technologies such as drone depth measurement.