The influence of sunlight on the measurement of slender steel pole inclination – A case study

Abstract Many factors cause the deformation of slender structures, such as the weather conditions that significantly affect their geometry. Surveys of such structures are critical for deformation monitoring and, therefore, general safety. Modern surveying methods like electronic tacheometry (ET), Global Navigation Satellite Systems (GNSS), laser scanning (LiDAR, terrestrial (TLS) and mobile (MLS)), and Unmanned Aerial Vehicles (UAVs) provide means for accurate and effective monitoring. Integrating surveying technologies paves the way for an exhaustive approach to slender structure monitoring and provides accurate data to detect deformation and intervene early. Electricity transmission poles exemplify such structures. The poles need to be monitored regularly to ensure operating stability and safety. The article reports a survey of tubular steel pole deflection angles at various times of the year and under various weather conditions. The surveys were accompanied by temperature measurements and a solar irradiance analysis. The maximum horizontal deflection of the pole top was found to be approximately 27 cm over a single sunny day, highlighting the dynamic nature of solar influence. The analyses yielded conclusions regarding measurements of slender steel structures. Specifically, the study confirmed that solar irradiance can cause short-term deflections of the pole top by up to 27 cm in a single day, and uncertainty increases proportionally with structural dynamics. Consequently, recording precise time and weather conditions during surveys is essential to improve rapid, time-constrained measurement accuracy and the operational safety assessment of slender steel structures. This should improve the measurement accuracy and operational safety of slender steel structures.