1. What is the principle of multi-period comparison?
Defects identified in each inspection are mapped to precise positions on the bridge’s 3D model, with projection accuracy at the pixel level. Overlaying data collected at different times allows direct comparison: whether the length and width of the same crack have changed, whether it has expanded, and whether new defects have appeared.
2. What value does multi-period comparison provide?
This capability turns scattered inspection records into a traceable development history, providing a basis for defect assessment and maintenance decisions, helping maintenance personnel identify expanding defects and arrange treatment priorities.
3. Applicable scenarios for multi-period comparison
| Scenario | Purpose |
|---|---|
| Crack development trend | Track length/width changes |
| New defect discovery | Overlay and compare old and new data |
| Maintenance decisions | Schedule by change trends |
4. Applicable conditions and scenarios
- Bridges with routine, multi-period inspection data
- Owners and maintenance agencies focused on defect development trends
- Defect history data retained long term for traceability
5. Notes
Multi-period comparison relies on a unified 3D model baseline and data retention policy; a routine inspection and data archiving mechanism is recommended.