Analysis of Survey Approach Using UAV Images and Lidar for a Chimney Study

UAVs for aerial photography have been promoted as the new way to map large areas efficiently. The cost of the technology is comparable to that of GNSS survey, and the results are comparable with much greater resolution. This is a major leap forward. The objective of this paper is to analyze the survey methodologies using a Lidar- and UAV-based photogrammetry and compare an overall approach over a chimney study. The whole analysis is done for a chimney under construction at Qasimpur, Harduaganj in Aligarh district in the Indian state of Uttar Pradesh. Chimney is one of the prominent structures in any thermal power plant, and its stability is really an issue for which conventionally total station and other instruments were used. The primary function of chimney is to discharge pollutants into atmosphere at such heights and velocities that the concentration of pollutants deemed harmful to the environment is kept within acceptable limits at ground level. Due to the development in unmanned aerial systems, survey has become quite accurate and accessible. Nowadays, it has been possible to study the structure more in detail and critical analysis can also be done using the point cloud data of the structure. Creation of mesh surface using these point cloud can be used to identify the undulation and defects in structure. In this paper, both UAV images and Lidar data are used to analyze the same structure from two different perspectives. Computing eccentricity of the structure using these two methodologies is further compared for accuracy, and an effort is made to understand the practicality of both survey methods.