# Predictive hybrid scan-to-BIM method improves heritage building documentation completeness and accuracy

## TL;DR

A new hybrid method combining laser scanning and drone photography improves the accuracy and completeness of building documentation for complex structures.

## Contribution

A predictive feasibility model and hybrid scan-to-BIM workflow that enhances documentation of complex buildings.

## Key findings

- Phase 1 achieved only 54% coverage due to occlusions and limited scanner placement.
- Phase 2 increased coverage to 96% by incorporating UAV photogrammetry and supplemental TLS.
- The PSFEM model shows potential for predictive planning to reduce site visits and improve BIM reliability.

## Abstract

Incomplete survey data often undermines the reliability of Building Information Models (BIM), particularly for structures with restricted access and complex geometries. This study demonstrates a hybrid Scan-to-BIM workflow that integrates terrestrial laser scanning (TLS) and unmanned aerial vehicle (UAV) photogrammetry, supported by a predictive feasibility concept, to improve documentation accuracy and completeness. A two-phase strategy was validated on a chapel case study. Phase 1, combining TLS and ground-based photogrammetry, achieved only 54% coverage due to severe occlusions and limited scanner placement. These results led to the formulation of a Predictive Scan Feasibility Estimation Model (PSFEM), designed to generalize site-specific parameters such as scanner range, clearance angle, and building height into a decision-support tool for future surveys. Guided by the recognition of Phase 1 limitations, Phase 2 incorporated UAV photogrammetry and supplemental TLS, increasing coverage to 96%. Comparative analyses confirmed consistency in accuracy and improved geometric completeness. While the PSFEM was developed retrospectively based on the limitations identified in Phase 1, its analytical validation demonstrates the potential value of predictive planning for reducing redundant site visits and enhancing BIM reliability. The proposed framework provides a transferable basis for applying predictive hybrid workflows in both heritage and complex building documentation. This workflow offers a practical and scalable method for Scan-to-BIM documentation, applicable to heritage as well as other complex buildings, enabling high accuracy and completeness while effectively managing time and resources.