Drawing Heritage Façades from 3D Data: Reprocessing LiDAR and Photogrammetry Datasets from OpenHeritage3D

Façade documentation requires detailed drawings that illustrate the dimensions, locations, conditions, and materials of a building exterior. This documentation aims to provide a guide and record for assessing, monitoring, preserving, and restoring built heritage. In 1858, a Prussian architect, Albrecht Meydenbauer, nearly fell while taking direct measurements at a building façade. This incident motivated him to develop an indirect measurement method called photogrammetry to record built heritage façades using a photographic camera and surveying instruments. In the era of analogue photogrammetry, photographic films and other equipment were costly. Consequently, such photogrammetric documentation projects required careful planning and skilled personnel. In the 21st century, the cost of personal computers and digital cameras reduced significantly. Collecting large amounts of data has become relatively inexpensive. Meticulous planning in photogrammetric projects has been de-emphasized, and tools like digital cameras, LiDAR scans, and UAVs have significantly increased the volume of unstructured data collected. CyArk, a non-profit organization based in California, has documented heritage sites globally using a combination of LiDAR and photogrammetry and published their datasets through the OpenHeritage3D portal, an open-access platform. However, these datasets often lack proper description, documentation, categorization, standardization, and modularization. Although these data can create photorealistic models, they do not contain surveying data and are too large to process for most personal computers. This project proposes a workflow for reprocessing these LiDAR and photogrammetric datasets produced by CyArk using widely available software like RealityCapture, AutoCAD, AutoCAD Raster Design, and the Bulk Rename Utility. The objective is to deliver traditional 2D façade documentation from LiDAR and photogrammetric data required for heritage conservation projects and to create guidelines for the future collection and storage of such large building documentation datasets. Preliminary results show that more emphasis should be placed on metadata, georeferencing, and data organization than has hitherto been made.