Long-Term Diagnostics of the Condition of the Choli Minaret in Erbil Using Photogrammetry and Laser Scanning

Abstract. Long-term documentation of historic monuments is essential for their preservation. This paper presents nearly twenty years of monitoring the 14th-century Choli Minaret in Erbil (Iraqi Kurdistan) using photogrammetry, geodetic methods, and modern laser scanning. Initial surveys in 2006–2008 established a detailed 3D model and control network, enabling evaluation of structural stability and supporting the subsequent restoration in 2009. A new campaign in 2025 employed a Trimble X7 laser scanner and photogrammetry, yielding datasets several orders of magnitude denser than earlier surveys. Comparison with previous measurements revealed no significant deformation or inclination of the minaret, with deviations remaining within tolerance (±2 cm) and surface roughness limits. The study confirms the structural stability of the monument but highlights persistent moisture issues at the base as a potential risk. The results demonstrate the value of long-term geodetic and photogrammetric monitoring, while also enabling future applications such as digital twins and VR/AR visualization for heritage conservation.